Dissertations / Theses on the topic 'Australian youth soccer players'

The purpose of this study was to develop a physiological profile of elite Australian Youth soccer players. Over three years, 150 players from the U'17, U'20 and U'23 national squads were tested for six measurements - height, weight, sum of eight skinfolds, vertical jump, maximum oxygen consumption and speed over twenty metres. Comparisons were made between those selected in the final team (classified as Successful) and those who failed to be selected (classified as Unsuccessful) to determine any significant differences between the two groups A physical and physiological profile was obtained for each player - expressed as a single value in both numerical and graphical formats. Players were ranked based on this score to determine significant differences between successful and unsuccessful players. Several significant differences (p<0.05) were found between Successful and Unsuccessful groups for a number of the variables primarily in the performance area rather than in the anthropometry parameters. For all squads, significant differences (P<0.05) were found between those who made the squad and those who did not when ranked based on their physical and physiological score. This study highlights the importance of the application of scientific testing to soccer Furthermore, it provides a system by which players' results can be analysed and ranked, and expressed in a format that provides the coach with immediate feedback as to an individual's specific strengths and weaknesses as a basis for training and team selection.

This thesis examined the physical development and match performance of elite youth academy soccer players some of whom were likely to progress to become professional soccer players. Physical characteristics such as standing height, body mass and estimated body fat composition, physical performance and match performance were explored. Furthermore, the relationships between physical performance and match running performance were examined in players from the U9 to U18 age group squads. Finally, the influence of biological maturity on physical characteristics, physical performance and match running performance in these elite youth soccer players was investigated and recommendations are made concerning talent identification and player development. One hundred and eighty-three elite soccer players (chronological age: 8.9 to 18.7 years; age grouping U9-U18) from an English Premier League Academy in the East Midlands were assessed for standing height, body mass, skinfolds, 30 m sprint, slalom and 505 agility, squat jump, counter movement jump with and without arms, Yo-Yo intermittent recovery test (level 1) and Multi-stage fitness test. All physical and performance variables measured in the study developed over time with chronological age except for the sum of 4 skinfold sites and estimated body fat composition (squad mean ± SD, U9 vs. U17: standing height, 139.4 ± 4.8 cm vs. 181.3 ± 5.6 cm; body mass, 33.6 ± 3.9 kg vs. 72.6 ± 5.7 kg; 30 m sprint, 5.26 ± 0.25 vs. 4.15 ± 0.11 s; slalom agility test, 4.83 ± 0.25 vs. 3.96 ± 0.09 s; counter movement jump with arms, 30 ± 3 cm vs. 48 ± 6 cm; the Yo-Yo intermittent recovery test (level 1), 787 ± 333 vs. 2617 ± 573 m). Standing height, body mass, 10, 15, and 30 m sprint times, performance on both agility tests, performance of squat jump and counter movement jump with arms; performance on the Yo-Yo intermittent recovery test (level 1) and on Multi-stage fitness test continued developing until the players reached the U17 squad. Moreover, the highest rate of development in standing height, body mass and all physical fitness tests occurred between the U9-U13 squads. Distance run during match play by 9 to 16 year old boys varied from 4056 (U9) to 7697 (U16) m per match (p < 0.05), and varied from 4675 to 6727 m·hour-1 of a match (p < 0.05). The U11-U16 squads covered a greater distance by high speed running (range: 487-553 mhour-1) compared to the U9 (178 m·hour-1) and U10 (219 m·hour-1) squads (p < 0.05 for all). Similarly, the percentage of time spent in high speed running by the U9 (1.1 %) and U10 (1.3 %) squads was less than that seen in the U11-U16 (2.6-3.0 %) squads (p < 0.05 for all). Chronological age accounted for 43% (p < 0.01), and the Multi-stage fitness test performance explained 7% (p < 0.05) of the variance in total distance covered per hour of a match in the U11-U16 group. Chronological age (p < 0.01) and the Multi-stage fitness test performance (p < 0.05) accounted for 10% and 11% respectively of the variance in percentage of time spent in moderate speed running. Chronological age accounted for 11 % of the variance in the percentage of time spent in high speed running (p < 0.01), whereas 30 m sprint and the Multi-stage fitness test performances explained 15% and 8% respectively of the variance in percentage of time spent in high speed running (p < 0.05 for both). The U9 and U10 squads showed a positive relationship between 20 m sprint time and distance covered in moderate speed running per hour of a match (r = 0.54, p < 0.05). In the U11-U13 squads relationships were evident between performance in 5, 10, 15, 20 and 30 m sprint (r = -0.67 to -0.46), the 3 standing vertical jumps (r = 0.46 to 0.73) and the 2 endurance tests (r = 0.45 to 0.60), and distance covered by moderate and high speed running per hour of a match (p < 0.05 for all). However, in the U14-U16 squads no significant relationships were evident. When stage of genital development was used to categorise players, standing height and body mass in the U12, U13 and U14 squads were positively influenced by biological maturity (p < 0.05 for all). The more mature players in the U13 squad also performed better in counter movement jump without arms and the Multi-stage fitness test (p < 0.05 for both). When stage of pubic hair development was used to categorise players, maturity status showed a positive influence on standing height and slalom agility test performance in the U12 squad (p < 0.05 for both) and on standing height and body mass in the U14 squad (p < 0.05 for both). When estimated chronological age at peak height velocity was used to categorise players, earlier maturing players were heavier (p < 0.01) and performed worse in counter movement jump without arms (p < 0.05) than later maturers in the U9 and U10 squads. Earlier maturers were taller (p < 0.01), heavier (p < 0.01) and possessed a thicker sum of 4 skinfold sites (p < 0.05) and higher estimated body fat (p < 0.01) compared to the later maturers in the U11 and U12 squads. Moreover, early maturers covered a greater distance than late maturers in the multi-stage fitness test (p < 0.05) in the U13 and U14 squads. In the U15 and U16 squads, early maturers were heavier and possessed thicker sum of 4 skinfold sites and higher estimated body fat compared to the late maturers (p < 0.01 for all). Furthermore, early maturers possessed a thicker sum of 4 skinfold sites (p < 0.05), higher estimated body fat (p < 0.01) and covered a shorter distance during the Yo-Yo intermittent recovery test (p < 0.01) compared to later maturers in the U17 and U18 squads. When stage of genital development was used to categorise players, the U12 and U13 players in stage 4 covered a greater distance in high speed running during a match than players in stage 3 (p < 0.05). There was a tendency for this still to be the case when distance was standardised into per hour of a match (p = 0.065). In the U9 and U10 squads, compared to later maturers, earlier maturers were given greater playing time during a match (p < 0.05), and consequently covered a greater distance during match play (p < 0.05). In the U13 and U14 squads, earlier maturers covered more distance per hour of a match and spent a higher percentage of time in high speed running when compared to their later maturing counterparts (p < 0.05 for both). In summary this research has provided the most extensive description yet of the physical characteristics, field test performance and match performance of elite youth soccer players. In addition, for the first time the effect of biological maturity (using 3 different methods of assessment) on a wide range of field tests and on match performance has been reported. The major changes in physical characteristics, field test performance and match performance between 10 and 14 years of age suggest that coaches should avoid as many selection decisions as possible during this age period, that they should take into account the fact that match distances covered at high speeds will be affected by maturity at these ages and that they should be aware that at present, coaches choose to give more mature players additional pitch time which obviously gives them an advantage in terms of playing development. An enhanced awareness of these findings in the coaching community could lead to an improved development and more appropriate selection decisions for elite youth soccer players in England.

Background: Football (Soccer) is arguably the most popular sport in the international sporting arena. A survey conducted by FIFA (Fédération International de Football Association) (FCPA, 2000) indicated that there are 240 million people who regularly play soccer around the world. Internationally, there are 300 000 clubs with approximately 1.5 million teams. In South Africa, there were 1.8 million registered soccer players in 2002/2003 (Alegi, 2004). Although youth players are predominantly amateurs and have no financial value for their clubs or schools, their continued health and safety are still of vital importance. There are some clubs which contract development players at 19 years of age in preparation for playing in their senior sides and these young players should be well looked after, to ensure a long career playing soccer. Being able to predict injuries and prevent them would be of great value to the soccer playing community. Aims: The main aim of this research was to create a statistical predictive equation combining biomechanics, balance and proprioception, plyometric strength ratios of ND/Bil (Non dominant leg plyometrics/ Bilateral plyometrics), D/Bil (Dominant leg plyometrics/ Bilateral plyometrics) and ND+D/Bil (Non dominant leg + dominant leg plyometrics/ Bilateral plyometrics) and previous injuries to determine a youth soccer player's risk of the occurrence of lower extremity injuries. In the process of reaching this aim it was necessary to record an epidemiological profile of youth soccer injuries over a two season period. It was also necessary to record a physical profile of, and draw comparisons between, school and club youth soccer players. Following the creation of the prediction model a preventative training programme was created for youth soccer players, addressing physical shortcomings identified with the model. Design: A prospective cohort study Subjects: Schoolboy players from two schools in the North West Province, as well as club players from three age groups were used for this study. Players from the U/16 and U/18 teams in the two schools were tested prior to the 2007 season. Players from the U/17, U/18 and U/19 club development teams were tested prior to the 2008 season. The combined total number of players in the teams amounted to 110 players. Method: The test battery consisted of a biomechanical evaluation, proprioceptive and plyometric testing and an injury history questionnaire. The Biomechanical evaluation was done according to the protocol compiled by Hattingh (2003). This evaluation was divided into five regions with a dysfunction score being given for each region. A single limb stance test was used to test proprioception. A Sergeant jump test was utilised using the wall mark method to test plyometric jumping height. A previous injury questionnaire was also completed on all players prior to testing. Test subjects from the schools were tested with the test battery prior to commencement of the 2007 season. The testing on the club teams was undertaken prior to the 2008 season. Injuries were recorded on the prescribed injury recording form by qualified Physiotherapists at weekly sports injury clinics at each of the involved schools and clubs. The coaching staff monitored exposure to training activities and match play on the prescribed recording forms. These training and match exposure hours were used, along with the recorded injuries for creating an epidemiological profile. Injuries were expressed as the amount of injuries per 1000 play hours. Logistical regression was done by using the test battery variables as independent variables and the variable injured/not injured as dependent variable (Statsoft, 2003). This analysis created prediction functions, determining which variables predict group membership of injured and non injured players. Results: There were 110 youth players involved in the research study from seven teams and four different age groups. There were two groups of U/16 players, an U/17 group, three U/18 groups and an U/19 group. The players were involved in a total of 7974 hours of exposure to training and match play during the seasons they were monitored. The average age of the players was 16.6 years. The majority of players were right limb dominant (83.6%) and 65.7% of players failed a single limb stance test. The mean jump height for both legs combined was 33.77cm, with mean heights of 22.60cm for dominant leg jump and 22.66cm for the non dominant leg. In the biomechanical evaluation of the lower leg and foot area, the average youth player presented with adaptation of toes, normal or flat medial foot arches, a normal or pronated rear foot in standing and lying and a normal or hypomobile mid-foot joint. Between 42.7% and 51.8% of players also presenting with decreased Achilles tendon suppleness and callusing of the transverse foot arch. The youth profile for the knee area indicated that the players presented with excessive tightness of the quadriceps muscles, normal patella tilt and squint, normal knee height, a normal Q-angle, a normal VMO: VL ratio and no previous injuries. This profile indicated very little dysfunction amongst youth players for the knee area. For the hip area, the youth profile was described as follows: There was shortening of hip external rotators, decreased Gluteal muscles length, normal hip internal rotation and no previous history of injury. Between 38.2% and 62.7% of players also exhibit shortened muscle length of the adductor and Iliopsoas muscles and decreased length of the ITB (Iliotibial Band). In the Lumbo-pelvic area there was an excessive anterior tilt of the pelvis with normal lumbar extension, side flexion, rotation and lumbar saggital view without presence of scoliosis. Between 58.18% and 65.45% of players presented with an abnormal coronal view and decreased lumbar flexion. Between 41.81% and 44.54% of players also presented with leg length, ASIS, PSIS, Cleft, Rami and sacral rhythm asymmetry. The similarity of the results for these tests in all players contributed to a new variable called 'SIJ dysfunction'. This was compiled from the average of the scores for Leg length, ASIS, PSIS, Cleft, Rami and Sacral rhythm, which was also considered for inclusion in the prediction model. The neurodynamic results of youth players indicated that approximately between 44.54% and 50.91% of players presented with decreased Straight leg raise and prone knee bend tests. The total combined dysfunction scores for the left and right sides were 17.091 and 17.909 respectively, indicating that there were higher levels of dysfunction on the right side than the left. This increased unilateral dysfunction could probably be attributed to limb dominance and increased use of the one leg for kicking and passing during the game. In the epidemiological study on youth players, there were a total of 49 training injuries and 52 match injuries. The total injury rate for youth players was 12.27 injuries/1000 hours, with a total match injury rate of 37.12 injuries/1000 match hours. The combined training injury rate was 7.17 injuries/1000 training hours. 87.13% of injuries were of the lower limb area and the individual areas with the highest percentage of injuries were the Ankle (25.74%), Knee (19.80%), Thigh (15.84%) and Lower leg (14.85%).The totals for youth players indicated that sprains (30.69% of total), strains (27.72% of total) and contusions (27.72% of total) were the most common causative mechanism of injuries. The severity of injuries show 'zero day' (no time off play) injuries to be the most common type (35.64%), followed by 'slight' (1 to 3 days off play) (33.66%) and 'minor' (4 to 7 days off play) (14.85%). School players had higher injury rates than club players but the severity of injuries to club players was higher, with longer absences from play. Non-contact injuries accounted for 52.47% of the total with 46.53% being contact injuries. School players had lower levels of non-contact injuries than club players, which correlated well with lower dysfunction scores recorded for school players during the biomechanical evaluations. This demonstrated that there was a definite relationship between levels of biomechanical dysfunction and the percentage of non-contact injuries in youth players, which formed the premise of the creation of a prediction model for non-contact youth soccer injuries. The next step in the creation of a prediction model was to identify the variables that discriminated maximally between injured and non-injured players. This was done using stepwise logistic regression analysis. After the analysis, ten variables with the largest odds ratios were selected for inclusion in the prediction model to predict non-contact injuries in youth soccer players. The prediction model created from the stepwise analysis presented as follows: P (injury)= exp(-8.2483 -1.2993a + 1.8418b + 0.2485c + 4.2850d + 1.3845e + 1.3004f-1.1566g + 1.8273h-0.9460i-0.5193j) l + exp(-8.2483-1.2993a + 1.8418b+ 0.2485c + 4.2850d + 1.3845e + 1.3004f-1.1566g + 1.8273h-0.94601-0.5193J) a = Toe dysfunction b = Previous ankle injury c = Ankle dysfunction d = SIJ dysfunction e = Lumbar Extension f = Straight Leg Raise g = Psoas length h = Patella squint i = Gluteal muscle length j = Lumbar dysfunction P = probability of non contact injury exp(x) = e x , with e the constant 2.7183 In the ankle area, the toe positional test, previous ankle injury history and combined ankle dysfunction score were included in the prediction model. In the knee area, the patella squint test was included in the model. In the hip area, the Psoas component of the Thomas test was included, along with the Gluteal muscle length test. In the Lumbo-pelvic area, the SIJ dysfunction (average of Leg length, ASIS, PSIS, Rami, Cleft and Sacral rhythm tests), lumbar extension test and lumbar dysfunction scores were included in the prediction model. In the neurodynamic area, the Straight leg raise test was included in the prediction model. The prediction model therefore contained tests from all five the bio mechanical areas of the body. Overall, this model correctly predicted 86.91% of players as either injured or not-injured. The I value (effect size index for improvement over chance) of the prediction model (1=0.67), along with the sensitivity (65.52%), specificity (94.87%), overall correct percentage of prediction (86.91%) and Hosmer and Lemeshow interferential goodness-to-fit value (X 2(8) = 0.7204), all demonstrated this prediction model to be a valid and accurate prediction tool for non-contact youth soccer injuries A second prediction model, for the prediction of hip and groin injuries amongst youth players, was also created. The prediction model created from the stepwise analysis for groin injuries presents as follows: P (Groin injury)^ exp(-116.2 + 33.5383d + 14.5108k + 4.1972m + 1.9330e + 10.7006f-14.4028n + 48.8751p) l + exp(-116.2 + 33.5383d+14.5108k + 4.1972m + 1.9330e + 10.7006f-14.4028n + 48.8751p) d = SIJ dysfunction k = Previous knee injury m = Previous hip injury e = Lumbar extension f = Straight leg raise n = Limb dominance p = ND/Bil plyometric ratio P = probability of groin injury exp(x) = ex, with e the constant 2.7183 The prediction model for hip and groin injuries included the variables of SIJ dysfunction, previous knee injury, previous hip injury, lumbar extension, straight leg raise, limb dominance and the ratio of non-dominant leg to bilateral legs plyometric height. When all the validifying tests were examined, the I-value (0.64868), sensitivity (66.67%), specificity (98.01%), false negatives (1.98%), false positives (33.33%), Hosmer and Lemeshow goodness-to-fit value (X2(8) = 0.77) and the overall percentage of correct prediction (96.26%) all reflected that this model was an accurate prediction tool for hip and groin injuries amongst youth soccer players. Conclusion: This study showed that it was possible to create a prediction model for non-contact youth soccer injuries based on a pre-season biomechanical, plyometric and proprioceptive evaluation along with a previous injury history questionnaire. This model appears as follows: P (injury)= exp(-8.2483 -1.2993a + 1.8418b + 0.2485c + 4.2850d + 1.3845e + 1.3004f - 1.1566g + 1.8273h - 0.9460i - 0.5193J) l + exp(-8.2483-1.2993a+ 1.8418b + 0.2485c + 4.2850d + 1.3845e + 1.3004f-1.1566g+1.8273h-0.94601-0.5193J) a = Toe dysfunction b=Previous ankle injury c = Ankle dysfunction d= SIJ dysfunction e=Lumbar Extension f = Straight Leg Raise g = Psoas length h = Patella squint i = Gluteal muscle length j = Lumbar dysfunction P = probability of non contact injury exp(x) = ex, with e the constant 2.7183 It was also possible to create a prediction model for non contact hip and groin injuries, which appears as follows: P (Groin injury)= exp(-116.2 + 33.5383d + 14.5108k + 4.1972m + 1.9330e + 10.7006f-14.4028n + 48.8751p) l + exp(-116.2 + 33.5383d + 14.5108k + 4.1972m + 1.9330e + 10.7006f-14.4028n + 48.8751p) d = SIJ dysfunction k = Previous knee injury m = Previous hip injury e = Lumbar extension f = Straight leg raise n = Limb dominance p = ND/Bil plyo metric ratio P = probability of groin injury exp(x) = ex, with e the constant 2.7183 It was also possible to create a prediction model for non contact hip and groin injuries, which appears as follows: P (Groin injury)= exp(-116.2 + 33.5383d + 14.5108k + 4.1972m + 1.9330e + 10.7006f-14.4028n + 48.8751p) l + exp(-116.2 + 33.5383d + 14.5108k + 4.1972m + 1.9330e + 10.7006f-14.4028n + 48.8751p) d = SIJ dysfunction k = Previous knee injury m = Previous hip injury e = Lumbar extension f = Straight leg raise n = Limb dominance p = ND/Bil plyo metric ratio P = probability of groin injury exp(x) = ex, with e the constant 2.7183 Using the hip and groin prediction model, combined with the injury prediction model, injuries in youth soccer players can be predicted. The data for each player should first be substituted into the injury prediction model, to determine the chance of getting injured during the season. The data should then be substituted into the hip and groin injury prediction model, determining the chance of hip and groin injuries during the season. The results from the groin injury prediction model could then be used to exclude groin injuries amongst players. A negative result for the hip and groin injury, which showed a false negative percentage of 1.98%, could be used to determine that an injury that was predicted using the overall injury prediction model, would not be a hip and groin injury. A positive result in the groin injury test could, however, not exclude injuries to other body areas that were predicted by the overall injury prediction model, so the groin injury prediction model could only be used to exclude hip and groin injuries.
Thesis (Ph.D. (Education)--North-West University, Potchefstroom Campus, 2009.

Sleep is a recurring state that is considered a critical process in the optimal attainment of daily functions and recovery in athletes. However individuals from elite sports, such as soccer, may be exposed to a number of situations that may impact sleep within the competitive season (such as inconsistent schedules and travel), which may result in sub-optimal sleeping patterns. However, research documenting the sleep of soccer players is at present limited. Therefore it would seem important to investigate how soccer players sleep to further the understanding of how sleep may be impacted. On this basis, the aim of the current thesis was to examine the typical sleeping patterns of youth soccer players and the factors effecting sleep. This was completed through a series of investigations conducted during the competitive youth soccer season. The aim of the first study (Chapter 3) was to validate a commercially available wireless sleep-monitoring device (WS). This was done in an attempt to provide a viable methodology to measure sleep within the habitual environment of soccer players. Nine randomly selected male participants were monitored over 3 nights and comparisons were made between the WS and other established field measures of sleep (Wristwatch actigraphy, sleep diary and Firstbeat bodyguard heart rate system). The relationships between the WS and the other sleep devices, indicated strong to very strong correlations (r > 0.6) and no significant differences between a range of outputs; total sleep time (Actigraphy assumed sleep time [0.97] & Sleep Diary [0.87] p > 0.05), sleep onset latency (Actigraphy [0.69] p > 0.05) and number of awakenings (Sleep Diary [0.69], p > 0.05). There were also low bias and narrow limits of agreement (LOA) within the comparison of mean differences with the WS for assumed sleep time (2 ± 17 min 95% LOA: -30 to 34 min [Actigraphy]), sleep onset latency (7 ± 17 min, 95% LOA -28 to 40 min [Actigraphy]), and number of awakenings (0.05 ± 1, 95% LOA -3 to 3 [Sleep Diary]). These results suggested that the WS is a viable device for the detection of these selected sleep variables. Chapter 4 looked to provide a comparison of sleep measures between a sample of youth soccer players (N=8) and non-athletes (N=8). Both groups were monitored over a period of 6 days within the habitual setting using the WS. The findings showed the soccer player group attained greater amounts of sleep quantity in comparison to the non-athlete group (504 ± 22 vs. 433 ± 46 min [+71 min] total sleep time, ES: 2.0, Large, p < 0.01). This may have been as a result of a later time of final awakening (08:54 ± 00:14 vs. 07:34 ± 00:46 [+77 min], ES: 1.7, Large, p < 0.01). Such an observation suggested that the soccer players were afforded greater time in bed as a result of the imposed soccer schedule. The soccer players also displayed a statistically greater time spent in wake (13(13) vs. 3(5) min [+10 min], PS: 0.86 ES: 1.5, Large, p < 0.05) on average each night. This data suggested that the sleep of the youth soccer players might be less efficient (as a consequence of greater levels of disturbance), despite desirable quantities of sleep being attained than non-athlete controls. Chapter 5 provided a daily comparison of sleep measures conducted over a 14-day assessment period. It is apparent that youth soccer players attained more sleep quantity in the nights preceding the match day (M-2: 488 ± 53 min [ES: 0.91, Moderate; p = 0.06] & M-1: 486 ± 64 min [ES: 0.84, Moderate; p = 0.02] respectively) in comparison to the night of the day after the match day (M+1: 422 ± 61 min). Such a finding suggested that youth soccer players adopt behaviours that reduce their sleep quantity on the designated recovery day (M+1) by >60 min, which may impact the recovery processes associated to this day. Relationships between sleep parameters and training and match load indicated a 100 au rise in RPELOAD (RPE * Duration) increased the time spent in wake (42 s [90% CI: 0 to 84 s]; ES: 0.36, Small; p = 0.098). It was also observed that an increase of 1000 m total distance increased the time spent in wake (40 s [90% CI: 5 to 75 s]; ES: 0.33, small; p = 0.06) A 100 m rise in high-speed running distance increased the number of awakenings observed (0.14 [90% CI: 0.03 to 0.25]; ES: 0.28, p =0.04) and the time spent in wake on average each night (1.5 min [90% CI: 0.78 to 2.3 min]; ES: 0.57, Small; p = 0.04). A similar outcome was observed in Chapter 6 were a 100 m rise in average high-speed running distance across three different 14-day training periods during the youth soccer season showed a 5 min increase in the time spent in wake on average (ES: 0.88, moderate; p = 0.04). Such outcomes provided a potential link between increases in training intensity (i.e. high-speed running distance) and sleep disturbances within youth soccer players. Increases in high-speed running distance also related to an increase of 24 min (90% CI: 12 to 36 min) on average for total sleep time (ES: 1.3, large; p < 0.01). Similarly increased high intensity heart rate (>85% max HR) was shown to effect total sleep time +20 min (90% CI: 6 to 32 min; ES: 0.87, moderate; p = 0.035). This may suggest that increases in intensity also may impact the amount of sleep quantity within youth soccer players. At present the mechanism for this response largely remains unknown. Within Chapter 7, a practical sleep hygiene strategy (10 min showering at ~40 °C, 20 min before time of lights out) was investigated. A group of ten youth soccer players were evaluated under normal sleeping conditions (control) and a shower intervention period, each consisting of three days within a randomized cross over trial design. Sleep information was collected using the WS. In addition to skin temperature, which was evaluated using iButton skin thermistors. The iButtons were used to establish both distal and proximal skin temperatures. This data was also used to create the distal to proximal gradient (average of distal measures – average of proximal measures = DPG). The data demonstrated that the shower intervention elevated distal skin temperature by (+1.1 °C [95% CI: 0.1 to 2.1 °C]; ES: 0.44, Small; p = 0.04) on average during a 10-minute period prior to lights out in comparison to the control condition. This elevation was also present during the first 30 minutes following lights out (1.0 °C [95% CI: 0.4 to 1.6 °C]; ES: 0.65, Moderate; p < 0.01), which was also accompanied by an increased DPG between conditions (0.7 °C [95% CI: 0.3 to 1.2 °C]; ES: 0.45, Small; p < 0.01). Additionally it was observed that on average the sleep onset latency of the youth soccer players was lower in the shower intervention condition (-7min [95% CI: -13 to -2 min]; ES -0.55, Moderate; p = 0.007). However no other sleep variable was affected as a result of the intervention. These findings demonstrate that a warm shower performed before lights out may offer a practical strategy to alter the thermoregulatory properties of distal skin temperature, which may advance sleep onset latency within youth soccer players.

As youth sport has become increasingly professionalized, many believe that the route to elite level play is through early specialization. Early specialization is a contentious issue, and many risk factors have been associated with high levels and intensities of training in youth. Youth today participate in highly competitive sport in pursuit of elite levels of play, recognition, and financial gain. Early specialization is thought to be a requirement for advancement, yet little is known about the early experiences of team sport athletes who grew up in the US. This is the story of 15 elite female athletes who “made it” to Division I soccer. The study offers us a window into the professionalized and commercialized world of youth soccer. It is a description of the childhood and adolescent journeys through sport and spans 10+ years of development. Through its telling, we learn about the expensive pay-to-play pipeline in soccer, we hear of the differences in opportunities that exist between social classes, and we confirm theories of expertise development. We learn that whether a young athlete specializes early or chooses to play multiple sports has little relevance to her progression to Division I. Through our thematic analysis of injury, we see how young athletes routinely play through injury, hide injury from coaches, and carry injury forward into their collegiate playing careers.

Background Organized sports offer an opportunity to promote physical activity and healthy eating. However, current data suggest that youth sports settings may not necessarily provide these benefits. In one study, youth were sedentary nearly half of a soccer match and in another foods and beverages offered at different youth sporting events were found to be energy-dense with little nutritional value. Parents, coaches and their respective sports organizations have the capacity to support a positive sports environment by promoting nutritious foods and beverages as well as optimal movement. To date, there is little research available on physical activity and sports trends of younger audiences, as well as perceptions of coaches and parents of young children toward sports snacks and policies to support healthy eating. The goal of these three studies were to better understand the youth soccer setting as an opportunity to address healthy eating and physical activity. Study 1 Objective: Assess snack offerings of parents and coaches of young soccer players, and policies. Methods: Beverage and Snack Questionnaires were distributed among all parents (n=120) and coaches (23) participating in recreational under five (U5) and under six (U6) soccer. The questionnaires assessed: socio-demographic information; types, as well as frequency, of snacks and beverages offered to children; reasons for snack and beverage choices; and attitudes toward snack policies. Results: Of the 44 parents and 23 coaches that participated, nutrition was ranked as the number one factor in choosing snacks and beverages for children participating in soccer. Yet parents and coaches reported offering many low-nutrient dense foods to their children as snacks. Coaches were receptive to limiting snack options and recommending healthy alternatives. Study 2 Objective: Observe snack offerings for young, recreational soccer players at combined practices and games to determine nutrient content and energy density of the foods and beverages provided. Methods: Snack observations for multiple, randomly selected teams were recorded using an observational checklist by trained researchers following all scheduled combined practices/games. Mean values across all snack foods and beverages were computed for the following key nutrients: calories, protein, fat, carbohydrates, fiber, sugars, and sodium. Results: Offered snacks were high in sugar, contributing nearly 77% of recommended total sugar intake per day, and low in sodium, fiber, and protein. Study 3 Objective: Determine the level of physical activity among young soccer players. Methods: Six random U5 and U6 teams were selected with 36 eligible players to participate in accelerometer collection data. Participants wore magnetic running pouches containing an accelerometer for a combined practice/game totaling 60 minutes. Informed, voluntary consent was obtained from each child and parent. Results: For the entire recorded session, average speed was 2.2 km/hour, average distance was 1.3 miles. Children were considered sedentary 55.0% of the recorded time. Discussion and Conclusions Organized sports settings offer an ideal avenue for promoting health and wellness among youth athletes. The current culture unfortunately promotes unhealthy snacking and sub-optimal physical activity. While the location and sample sizes limit generalizability, our results support research conducted with older children and highlight the importance of nutrition education for parents and coaches, as well as the potential for snack policies and strategies to encourage more vigorous physical activity in youth sports settings.
Master of Science

Based upon postulates derived from the Developmental Model of Sports Participation (Côté et al., 2012) we tested the effects of domain specific activities (play and practice), as well as sporting diversity during the sampling years, on the development of motivation, passion and skill ratings. The first component of our study required testing predictions that play and diversity during the sampling years (age 5-12 yr) were positively correlated with intrinsic motivation and passion. We questioned elite youth level soccer players (N= 148), across 3 age groups, who were on the pathway towards achieving professional status at the adult level. Overall, we found no significant correlations between play and early sporting diversity during the sampling years with scores of motivation or passion. A small, yet significant positive correlation was observed between accumulated hours in soccer practice and integrated regulation. However, independent analysis of age groups yielded significant negative correlations between hours accumulated in soccer practice and measures of intrinsic motivation (Under 15 yr) and harmonious passion (Under 17 yr). The second study component investigated associations between time spent in soccer activities during the sampling years and across participants’ full careers as well as sporting diversity with coach ratings of skill. For the U17 group, hours accumulated in organized practice were related to creative and overall skill, while accumulated hours in soccer practice were related to technical skill for the U15 group. Moreover, for the U17 group, % accumulated hours in play negatively correlated with technical and overall skill ratings. The youngest group (U13) showed a different pattern of results to the older players, with more hours in play (% and total) related to creative skill. Due to these overall relationships, we conclude that recommendations towards early sporting diversity and more time in deliberate play activities (i.e., individually-led practice or play) should be treated with caution, because they do not inoculate against any hypothesized negative effects of early specialization in sport and are negatively related to predictors of skill (at least for the older players). Follow-up longitudinal analysis is recommended to determine how these practice and motivation variables are related to future success.

Youth soccer players are required to play multiple matches within a short period of time. Participation in congested match schedules like youth soccer tournaments can result in fatigue and a decline in physical performance. The purpose of this study was to examine changes in countermovement jump height variables and sprint time to determine if physical performance was altered. Fourteen youth female soccer players performed countermovement jump testing pre, post-match, and post-tournament, and sprint testing pre and post-tournament. Jump height differed significantly (p <0.001) between time periods during the tournament, and sprint time increased by a statically significant amount (p = 0.001). Results also indicated that there were significant effects on CMJ variables; RSImod (p = 0.015), eccentric impulse (p = 0.022), concentric impulse (p = 0.010), peak power (p = 0.044). It was concluded that certain CMJ variables are sensitive to fatigue as well as sprint time and may be useful for coaches to use to monitor fatigue and determine recovery strategies and proper training load before and after a youth soccer tournament.

BACKGROUND: Concussions in youth sports are growing in prevalence. This “invisible injury” can cause permanent brain damage and even death. An increased understanding of how youth athletes view the injury is imperative in improving education and developing more effective return-­‐to-­‐play protocols. OBJECTIVE: To examine if history of concussion is associated with a difference in knowledge, attitudes, and perception of concussive injuries in youth soccer players. METHODS: We conducted a survey of youth soccer players aged 14 to 18 years. Players were recruited from Tucson Soccer Academy in Tucson, Arizona. RESULTS: Surveys were obtained from 90 athletes, with 32 (36%) previously sustaining at least one concussion. On average, participants responded “correctly” to 77% of attitude questions and 81% of knowledge questions. There was not a significant difference in knowledge of or attitude towards concussion between previously concussed and non-­‐concussed athletes; however, females scored significantly higher on knowledge questions than males. CONCLUSIONS: This study shows a high level of awareness of concussion in youth soccer players, while still highlighting a need for education. Limited distinctions were made among subgroups of players, suggesting directions of future research in investigating the role, if any, outside factors have on knowledge and perception of concussion.

Psychosocial factors are the interrelated psychological, social and/or behavioural considerations that can influence talent development in football (Holt & Dunn, 2004). Despite this, the significant growth of female football worldwide, and the psychosocial challenges faced by female athletes during adolescence, scant scholarly attention has been afforded to the role of psychosocial factors in the development of talented female football players. Therefore the main aim of this thesis was to understand psychosocial factors associated with talent development in UK female football players. Study one systematically reviewed the literature on psychosocial factors associated with talent development in soccer. Following an extensive literature searching, selecting and appraisal process, three overarching themes of psychological, social and behavioural factors associated with talent development in soccer - underpinned by a total of 33 subthemes were created. The appraised literature has a moderate-to-high risk of reporting bias; had a significant bias towards adolescent, Caucasian, male, able-bodied, and European soccer players; and extant literature has demonstrated bias towards quantitative approaches and retrospective data collection methods. Consequently, study two began to address these reported biases by longitudinally and prospectively investigating the developmental experiences of English elite female youth soccer players. Through interviews, fieldwork and the use of composite sequence analysis, study two forwarded the importance of psychosocial considerations including the interaction between players and key social agents (soccer fathers, soccer brothers, soccer peers and non- soccer peers), elements of self-regulation and volitional behaviours, and the subsequent developmental benefits for their soccer careers. However, this study did not address the experiences of those who were unsuccessful in their attempts to achieve an elite female soccer career, nor did it collect primary data from other key social agents. Building on the critique of study two, study three sought to adopt an underutilised approach of negative case analysis by examining the experiences of players who had been unsuccessful in their attempts to forge a career in female soccer. Based on interviews former female players, their best friends, coaches and teachers, a grounded theory of talent and career development in UK female youth soccer players was produced. The theory posited that interactions with multiple social agents can affect the quality of talent development and learning environment that a player experiences, which can lead to adaptive player level benefits and changes (e.g., basic psychological need satisfaction; development of pertinent intra-individual constructs; optimal match preparation and training behaviours) and create a greater chance of career success. Study three also forwarded important culturally significant considerations for practitioners working with UK female soccer players, such as an understanding of dual career demands and the impact of role strain on female players. However, study three did not test any of the theoretical predictions offered by the grounded theory. Owing to the need to test predictions of grounded theories to assess their predictive validity, study four sought to test key predictions using a representative sample of English talented and elite adolescent female soccer players (N=137). As a result of the limited structural stability of the Basic Needs Satisfaction in Sport Scale and the Talent Development Environment Questionnaire (as demonstrated by significant cross loading of items, high bivariate correlations between subscales, and one example of an inadequate Cronbach s alpha), data was parcelled and the revised path hypothesis: perceptions of talent development environment > basic psychological needs satisfaction > career aspirations and beliefs > career intentions was produced. Path analysis supported the hypothesis. Supporting findings of studies two and three, regression analysis demonstrated that playing level positively predicted career beliefs, aspirations and intentions; whereas age negatively predicted these variables. Finally, TDEQ results indicated a perception that UK female soccer players that they can be written off before having the opportunity to fulfil their potential. Overall, this thesis has provided original and unique contributions to the sport psychology literature by enlightening the body of research to the developmental experiences of English female youth soccer players. It provides a developmental understanding scarcely evident in existing talent development literature. The interactional roles of multiple social agents have been elucidated and linked to psychosocial development, behavioural outcomes and talent and career progression within talented female players. The thesis has extended previous approaches to talent development in soccer by testing the predictions of the grounded theory. Initial evidence suggests that the proffered grounded theory is robust; however further research utilising structurally sound and ecologically valid measures would serve to further validate these claims.

Training stress in the absence of adequate recovery has been associated with a decrease in well-being and performance. Thus, there is potential for the high training and competition loads that elite English youth football players experience to have a negative effect on wellbeing and performance. The aim of the thesis was to assess the utility of well-being and physical performance assessments in managing the development of elite English youth football players. The first study (Chapter 4) examined the sensitivity of a subjective well-being questionnaire (WQ; developed ‘in-house’ by sport science practitioners at a category two academy and only taking < 30 s to complete), by comparing the player’s next day responses between two acute training bouts of varied duration; 15 mins (low load) compared to 90 mins (high load) high intensity intermittent exercise (Loughborough intermittent shuttle test, LIST). WQ items showed small to large deteriorations following the high load compared to low load (d=0.4-1.5, P=0.03-0.57). The ability of the WQ to differentiate between responses to high and low training loads indicated that this questionnaire could be used to detect training induced stress prior to training on a daily basis throughout the season. Other modes of monitoring assessment evaluated were either not sensitive to differentiate between high and low loads (countermovement jump; CMJ) or detected differences between high and low training load responses (HR indices) but lacked utility in detecting individual changes. The second study (Chapter 5) applied well-being and physical performance assessments to elite English youth football players during a high intensity, low volume pre-season training period. Trivial changes in perception of WQ items of sleep, recovery, appetite, fatigue, stress and muscle soreness were observed across weeks (P=0.35-0.93, 2 P  =0.02-0.08) with no negative WQ responses evident. Internal training load was lower to a large extent in week 1 (P= < 0.001, 2P  =0.54) yet no differences in internal training load were evident across weeks two, three, four and five. Trivial to small associations (r=-0.21 to 0.19) between internal training load and WQ responses were observed. Small to moderate improvements in aerobic performance were evident post training in comparison with pre training (P < 0.001-0.53, d= 0.33 – 0.94) with a large to moderate improvement in submaximal HR measures (P < 0.001 – 0.09; 2 P  = 0.34 - 0.74) observed across the training weeks. Trivial to moderate impairments in neuromuscular performance were evident post training in comparison with pre training (P < 0.001 – 0.21; d=0.17 – 1.00). Collectively, the preservation of well-being prior to each training session during a pre-season period and improvements in aspects of physical performance were indicative of a balance between stress and recovery. The third study (Chapter 6) examined player perceptions of well-being and physical performance across a season in Elite English youth football players. Increases in training exposure (P < 0.05; 2 P  =0.52) and moderate to large deteriorations in perceptions of well-being (motivation, sleep quality, recovery, appetite, fatigue, stress, muscle soreness P < 0.05; 2 P  =0.30-0.53) were evident as the season progressed. A large improvement in Yo-Yo intermittent recovery test performance (Yo-Yo IRT; P < 0.05; 2 P  =0.93) and a small to moderate impairment in neuromuscular performance (P > 0.05; 2 P  =0.18 - 0.48) was observed as the season progressed. These findings show an imbalance between stress and recovery in English elite youth football players even when players experienced lower training exposure than stipulated by the elite player performance plan (EPPP). In summary, this thesis highlights the potential utility of subjective well-being assessments to inform the management English elite youth football player development. Furthermore, it highlights the high training volumes that English elite youth players are exposed can potentially lead to an imbalance between stress and recovery.

The aims of this thesis were to examine the relationships between relative age, maturity status, and physical phenotypes on the selection, playing position allocation, and development tempo of a broad sample of elite youth soccer players’ that best represents UK development programs governed by the Elite Player Performance Plan (EPPP). The first research study (Chapter 4) aimed to establish the short-term reliability (STR) and smallest worthwhile changes (SWC) for a battery of field tests commonly used to assess elite youth soccer players’ physical and somatic phenotypes. On two occasions, the within-practitioner STR of three anthropometric measures (stature, seated height and body-mass) were assessed to estimate age at peak height velocity (APHV). In addition, within-player STR of the Multi-Stage Fitness Test (MSFT), 10 and 20 m sprints were assessed using 45 elite youth soccer players (age: 13.5 ± 1.5 years; body-mass: 49.2 ± 10.3 kg; stature: 177.7 ± 6.4 cm). In addition, within-player STR was established for T-Test and counter-movement jump (CMJ) performance using 21 senior amateur soccer players (age: 24 ± 5.3 years; body-mass: 84.3 ± 7.1 kg; stature: 177.7 ± 6.4 cm). The within-practitioner STR (coefficient of variance [CV], (95% confidence interval [CI])) and SWC were established for anthropometric measures (stature: CV = 0.4 % [CI = 0.3 to 0.5 %], SWC = 2.3 cm; seated height: CV = 1.1 % [0.9 to 1.4 %], SWC = 1.1 cm; body-mass: CV = 0.7 % [0.6 to 0.9 %], SWC = 2.3 kg) and APHV (CV = 0.8 % [0.7 to 1.0 %], SWC 0.1 year) respectively. Within-player physical fitness reliability and SWC were also established for CMJ (CV = 5.9 % [4.6 to 9.0 %], SWC = 0.6 cm), T-Test (CV = 1.7 % [1.3 to 2.4 %], SWC = 0.08 s), 10 m sprint (CV = 2.7 % [2.2 to 3.4 %], SWC = 0.03 s) and 20 m sprint (CV = 4.9 % [4.1 to 6.4 %], SWC = 0.06 s) performances. This battery of anthropometric and physical fitness field tests observed a high level STR and produced SWC values that will permit talent development (TD) practitioners to implement SWC % to assess changes in player growth, maturity and physical fitness. Research study 2 (Chapter 5) aimed to quantify the relative-age effect (RAE) and examine differences in physical phenotypes owing to the RAE of 731 (U11 to 18) elite youth soccer players sampled from 17 UK soccer development centres. Chi-squared analysis identified a clear un-even birth distribution across all age groups, demonstrating an over-representation of players born in the first quartile (Q1) (U11 to 12: 39%; U13 to 14: 46%; U15 to 16: 57%; U17 to 18: 42%) in comparison to Q4 (U11 to 12: 13%; U13 to 14: 8%; U15 to 16: 8%; U17 to 18: 14%) of the selection year that significantly differed to the distribution expected from National census data (all ≤ 0.001). Small to moderate differences in player stature and body-mass were identified for U11 to 14 players, whereby players born in Q1 were both heavier (ES = 0.48 to 0.57) and taller (ES = 0.62 to 1.06) than players born in Q4. U11 to U12 and U17 to 18 players born in Q1 were generally (ES = 0.37 to 0.70) more mature than their relatively younger (Q4) counterparts. There were no significant differences in agility (P = 0.108 to 0.643), 10 m (P = 0.122 to 0.886) and 20 m (0.090 to 0.911) sprint times between Q1 and Q4 players. However, relatively younger (Q4) U15 to U16 players showed small to moderate (ES = 0.34 to 0.49) inferiority in MSFT performance that continued for Q2 (Q2 vs. Q4: P = 0.041, ES = 0.91). The obvious birth distribution bias identified within this chapter favours the selection of players who are born earlier in the selection year, who possess enhanced maturity related anthropometric and aerobic performance characteristics. Study 3 (Chapter 6) assessed the contribution of relative age, maturity and physical phenotypes upon soccer playing position allocation (goalkeeper [GK], central-defender [CD], lateral-defender [LD], central-midfield [CM], lateral-midfielder [LM], and forward [FWD]) in 465 elite-youth soccer players (U13 to U18`s). U13 to 14 CD were identified as being relatively older than LD (ES = 0.72). CD and GK were generally taller (U13 to 14: ES = 0.49 to 1.19; U15 to 16: ES = 0.72 to 1.48; U17 to 18: ES = 0.96 to 1.58) and heavier (U13 to 14: ES = 0.64 to 1.40; U15 to 16: ES = 0.24 to 1.57; U17 to 18: ES = 0.51 to 1.32) than other players at each developmental stage and were advanced maturers at U13 to 14 (ES = 0.63 to 1.22). Position specific fitness characteristics were distinguished at U17 to 18, where LD and LM were faster than their central counterparts (10m: ES = 0.72 to 0.83; 20m: ES = 0.94 to 1.07). In summary, relative age, maturity and anthropometric characteristics appear to bias the allocation of players into key defensive roles from an early development stage, whereas position-specific physical attributes do not become apparent until the latter stages (U17 to 18) of talent development in outfield players. Study 4 (Chapter 7) assessed the development tempo of anthropometric and physical fitness characteristics according to players decimal age and maturity offset (YPHV) of 969 (U9 to U18) UK elite youth soccer players using battery of 7 field tests. Segmented regression analysis established that estimated stature increases were highest between 10.7 (CI = 10.2 to 11.2) to 15.2 (CI = 14.8 to 11.2) years, and between -3.2 (-3.5 to -2.9) to 0.8 (0.5 to 1.1) YPHV, with estimated annual growth rates of 7.5 (CI = 7.0 to 7.9) and 8.6 (CI = 8.3 to 9.0) cm·year-1 identified for decimal age and YPHV, respectively. Estimated rate of body-mass developmet was also increased (7.1 [CI = 6.6 to 7.6] kg·year-1) between 11.9 (CI = 11.5 to 12.3) to 16.1 (CI = 15.5 to 16.7) years of age, whereas when modelled against somatic maturity, body-mass increases continued at 7.5 (CI = 7.2 to 7.7) kg·year-1 from -1.6 (CI = -2.1 to -1.1) to ~4.0 YPHV, without plataeu. Estimated CMJ development tempo decreased from 2.5 (CI = 2.2 to 2.8) to 1.3 (CI = 0.7 to 1.9) cm·year-1 circa- PHV (0.6 [-0.4 to 1.6] YPHV). Estimated T-Test performance gains ceased from 15.8 (CI = 15.2 to 16.4) years of age onwards, but when modelled against somatic maturity status, improvements slowed by ~43% at 0.4 (CI = -0.1 to 0.9) YPHV. Players estimated endurance capacity increased by 169 (CI = 158 to 179) and 185 (CI = 173 to 198) m·year-1, until 16.4 (CI = 15.9 to 17.0) years and 2.1 (CI = 1.6 to 2.5) years post PHV, respectively. Estimated 10 and 20m sprint performance increased until 11.8 (CI = 11.2 to 12.5) years of age, or -1.8 (CI = -2.5 to -1.0) YPHV, before development tempo increased (31-43%) until 15.8 (CI = 15.3 to 16.3) years, or 1.2 (CI = 0.1 to 2.3) to 1.3 (CI = 0.8 to 1.8)YPHV. Findings identified that model strength for stature and body-mass was slightly higher in YPHV (r2 = 0.89) versus decimal age (r2 = 0.81). However these trends were not apparent for the development of physical fitness attributes. In addition, Chapter 7 revealed that players estimated sprint performance development markedly increased (31 to 43%) between 11.8 years and 15.8 years, or 1.2 to 1.3 YPHV. This data will provide practitioners with a guide to help forecast players’ rate of anthropometric and physical fitness characteristics development at an early stage of their development. Findings here’s suggest that TD practitioners should systematically use estimates of maturity offset to reduce the premature deselection of equally talented but slower players who may reach the same sprint capacity in adulthood, but are slightly later maturers versus there team-mates. In summary, the standardised battery of field-tests used within this thesis observed high levels of STR. There was a clear birth distribution bias that favours the selection of players’ for UK elite soccer development centres, who are born earlier in the selection year. It is likely that transient anthropometric advantages afforded to relatively older players within younger age categories act as a major contributory factor that bias the premature selection and role allocation of these players in to key defensive (GK and CD) roles, before the development of position-specific physical attributes become apparent during the latter stages (U17 to 18) of the EPPP in outfield players.
Likely to be of particular importance to TD practitioners, players’ estimated sprint performance development increased across decimal ages (11.8 to 15.8 years) spanning PHV (-1.8 to 1.3 YPHV), justifying research to further examine the intricacies between training prescription and maturity on sprint speed development. Monitoring player maturity will enable a better understanding of maturity related anthropometric and performance gains, and is likely to improve sensitivity of training prescription and physical phenotype development forecasting. Emphasising the necessity for systematic and consistent monitoring of player growth and maturity that will likely inform talent identification and development processes, and reduce the biases associated with relative age and anthropometric advantages upon talent selection and positional role allocation.

Thesis (M.A.) -- University of Maryland, College Park, 2005.
Thesis research directed by: Dept. of Kinesiology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Lower extremity non-contact injuries are common in male youth soccer players. Altered neuromuscular control defined as muscle strength, power or activation patterns that lead to increased joint loads has been suggested as a mechanism that underpins the occurrence of these injuries during rapid deceleration tasks. However, data pertaining to neuromuscular risk factors and screening in male youth soccer players is sparse. The purpose of this thesis was to investigate the validity of a novel movement screen to predict injury risk in elite male youth soccer players. Study 1 examined the test re-test reliability of a range of field-based neuromuscular control tests reporting acceptable values for measures of single leg dynamic balance, landing force, maximal hop distance and tuck jump knee kinematics; however, other commonly used assessments were more variable. The effects of chronological age on the measures deemed reliable in study 1 were then analysed in study 2. A number of between group differences were evident but this pattern was variable across the different constructs of neuromuscular control, thus an age-specific training emphasis may be required at different stages of a young player‟s development. Also, the normative data included for a range of chronological age groups in this study may be useful for practitioners, from which fluctuations in performances can be identified. The results of study 3 showed acceptable within subject variation on the majority of the tests measured at three time points across a soccer season. However, percentage change scores in neuromuscular control were more variable and differences between test sessions were often considerably lower than the random variation, thus observed changes may not be meaningful. However, single leg countermovement jump forces increased considerably throughout the season indicating that a „real‟ change occurred and this may be associated with greater injury risk. Seasonal variation in injury occurrence was also identified in study 4, but a major finding was a three-fold increase in player incidence rate since the introduction of an early soccer specialisation model in the United Kingdom. This indicates that elite male youth players are now at a greater risk of injury. The final study examined the ability of a novel movement screen to predict non-contact lower extremity injury risk in male youth soccer players. A combination of anthropometric and neuromuscular risk factors were shown as predictors, but there was variability across the different chronological age groups. Single leg countermovement jump landing force asymmetry was the most frequently reported risk factor and univariate analysis also identified a number of significant predictors in respective chronological age groups. The results of this study provide an evidenced-based diagnostic assessment tool from which “at risk” players could be identified; the injury prevention asymmetry soccer screen (i-PASS). However, greater weightings of specific assessments may be required at different stages of a child‟s development due to variability across age groups. This thesis has made an original and significant contribution to the existing paediatric injury risk screening literature for soccer players. Furthermore, these findings can easily be applied by practitioners to more accurately screen their players and develop targeted prevention strategies to reduce injury risk.

Abstract Background: Football is among the world’s most popular sports. It is played all over the world. The sport is an intermittent team sport with demands on technical, tactical, psychological and physical abilities. This study focused on the physical ability and more specifically sprinting and agility. Youth national teams are selected every year from the age of 15 and the Swedish Football Association are funding camps and friendly matches were this selected few youth players are being educated in technique, tactics, psychology and physical training. Due to the selections for the national teams taking place at the age of 15, youth players can be affected on how far they have come in the biological maturation. Aim: The aim of this study was to compare linear speed and non-reactive agility between youth football players selected or not selected for the national team. Method: The study was an observatory cross-sectional study. Twenty-three subjects from an elite club in Sweden were divided into two groups. Eleven subjects had been to a national team gathering (n=11) and twelve players from the same teams had not been invited and was one group (n=12). The subjects performed a linear sprint test and a non-reactive agility test to compare differences between the two groups. The linear sprint test consisted of a 20-meter sprint with split times at 5 and 10 meters. The non-reactive agility test was a zigzag-test over a total of 15 meter. Both tests used timing gates to record time. SPSS was used for the statistical analysis. Results: There was a statistically significantly difference (p<0.050) between the groups in the linear sprint. The national team group ran 6.6% (p=0.003) faster in the 5-meter sprint test, 2.4% (p=0.020) faster in the 5-meter sprint test and 3.4% (p=0.007) faster in the 20-meter sprint test. There were no statistically significant differences (p>0.050) in the non-reactive agility test. Conclusion: This study found a difference in sprinting ability and it could be due to the difference in the maturation phases. The biggest difference was in the shortest distance, indicating that shorter sprints are more important to develop over longer sprints. The non-reactive agility test showed no statistically significant differences. Future studies could investigate speed and agility separate with larger groups of participants and follow them over time to see if the difference in both speed and agility evens out over time, when all participants have gone trough the final stages of maturation.

Elite youth soccer player’s performance depends on a multitude of factors (Stølen et al. 2005). Muscular force production capability is of likely importance due to the frequency of powerful actions that occur within match play (Faude et al. 2012). Little is known though of the training undertaken at elite youth soccer academies to increase muscular force production capabilities particularly across maturation groups. There is also little evidence around the nature, or genetic influence on this variable in these populations. Greater knowledge on these areas would be beneficial to aid an understanding of performance and to plan practical interventions. Eight weeks of training for players in the under 9 (U9) through to under 21 (U21) age groups (Chapter 3) were recorded to investigate the duration of each training type completed. The total training duration increased from U9 to U14 before reducing at U15 and then remaining unchanged through to, and including, the U21 age group. Soccer training accounted for 97 ± 4 % of session time in the U9 to U14 groups and 74 ± 3 % in the U15 to U21 groups. The remainder of training was made up of work that was not soccer based. The data in this case study suggest that training time is focussed on the technical/tactical development throughout the academy, particularly in the younger age groups. Study 2, part A (Chapter 4) provided baseline isometric maximal voluntary force (MVF) data for players and an maturation-matched non-elite control group. MVF was slightly higher in the elite compared to control cohorts during an isometric mid-thigh pull (IMTP, 118.29 ± 13.47 N compared to 109.69 ± 17.00 N). Such data may indicate that ability to produce force, specifically isometric MVF, may not be a crucial determinant of performance in elite youth soccer based on this sample. The purpose of study 2, part B (Chapter 4) was to establish the effect of 8 weeks typical training on elite youth soccer players’ IMTP MVF. This was also compared to a non-elite control cohort matched for maturation status and not undertaking training. Isometric MVF did not change in either group over the 8 week period (P = 0.386). These data suggest that this elite youth soccer training simply maintained current strength levels and was not sufficient to elicit increases in isometric MVF. Study 3 (Chapter 5) examined variations in four separate genes, all identified as potentially having an influence on muscular force production capabilities: PPARA rs4253778, NOS3 rs2070744, COLIA1 rs2249492 and VDR rs2228570. Allele and genotype frequency was determined along with the influence of those single nucleotide polymorphisms (SNPs) on isometric MVF. Only NOS3 was different in genotype distribution between cohorts with TT genotype showing 45.0 % and 30.4 % frequency in elite and control cohorts respectively (P < 0.001). Furthermore, no difference was seen between cohorts for isometric MVF data when comparing influence of any genotypes of any gene. These data provide novel information around genotype frequency in this population and would suggest that the gene variations examined here might not play a role in force production in these populations. Overall, these findings suggest that muscular force production may be important for elite youth soccer performance, but that current training practices to improve this characteristic should be revised. This seems especially relevant given the lack of genetic association with force production in the gene variations examined here, i.e. elite youth soccer players do not appear to be selected based on a genetic predisposition for greater isometric force production capabilities.

Aim: The aim of the present study was to examine the outcome of repetitive-part training and dual-task training in the acquisition of dribbling technique and decision making in prepubescent novice soccer players. Method: Twenty four preschool pupils, with an age of 6.2 ± 0.4 years (mean ± SD) and with no previous experience of partaking in any organized team or ball sport participated in the study. The participants were tested (pre test) for initial performance level of dribbling technique and decision making and were then divided into two balanced experimental groups. The repetitive-part group underwent four weeks of part-task training (isolated dribbling-technique training) which were followed by four weeks of dual-task training (simultaneous training of dribbling technique and decision making). The dual-task group underwent eight weeks of dual-task training. The outcome in acquisition of dribbling technique and decision making was examined after four (mid test) and eight (post test) weeks of training. Both training regimes were followed by four weeks of non-training and thereafter a test (retention test) of the retention effects was carried out. Effect sizes (d) of the acquisition within each group and of the difference in performance and acquisition between the two groups were evaluated based on Cohen's effect size criteria (|d| > 0.2, small effect; |d| > 0.5, moderate effect; |d| > 0.8, large effect). Results: Between the pre and mid test, both groups showed large improvements in dribbling technique. The corresponding improvement was small in the repetitive-part group and moderate in the dual-task group between the mid and post test. There were large differences between the groups' decision-making performances at the mid, post, and retention test where the dual-task group was superior to the repetitive-part group. The dual task group showed large improvements of decision making between the pre and mid test. Between the mid and post test, the corresponding effect was large within the repetitive-part group and moderate in the dual-task group. The improvement of the dual-task group's decision making between the pre and mid test was greater than the corresponding improvement showed by the repetitive-part group, between the mid and post test. This difference produced a moderate effect size. Conclusions: These findings challenge conventional repetitive-part training regimes and, with references to previous research, emphasize the importance of dual-task training for skill acquisition in prepubescent novice soccer players.

Background: Plyometric training is a form of conditioning with increasing popularity that involves the performance of body weight jumping type exercises with the use of the stretch-shortening cycle muscle action. It is widely accepted that plyometric training has beneficial effects on many sports, including soccer. Objectives: To assess the effect of plyometric training on explosive actions of soccer performance (sprinting, jumping, agility, ball kicking) and indicated the kind, the frequency and targeted age groups on which the plyometrics should be executed. Methods: A search for all types of trials was performed on Pubmed, Web of Science and Sport Discus databases and the results were recorded according to PRISMA recommendations. 24 studies were included and judged for risk of bias and quality of evidence according to Cochrane guidelines and GRADE. Results: The studies were judges to have “low”, “high” and “unclear” risk of bias and were judged as “moderate”, “low” and very low quality of evidence. The finding of most of the studies show that plyometric training has beneficial effects and statistically significant improvements on the explosive actions (sprinting, jumping, agility and ball kicking) of young soccer players between 10 and 19 years old. Conclusions: The level of evidence of the review is moderate which means that further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. The current study suggests that plyometric training can be beneficial for young soccer players when is applied with gradual intensity, frequency of 2-3 times per week and along with regular soccer and strength training. Future research of higher quality of evidence studies and lower risk of bias should be performed in this field.

Abstract Aim The main purpose of this study was to investigate and compare the effects of a very heavy resisted sprint training regimen and a unresisted sprint training regimen on sprint, acceleration and jump performance in late pubertal adolescent football (soccer) players at mid- to post-PHV and >95% PAH. Method In total 27 male football players were recruited as volunteer participants. The participants had no previous experience with resisted sprint training. The participants were randomly assigned to either the resisted sprint (RST) (n=9) or unresisted sprint (UST) (n=10) training group. However, the grouping was matched based on the force-velocity (F-v) profiling. A control group (i.e. TAU group n=8) was matched with the experimental groups based on age and anthropometrics. The training was done twice a week for four weeks, consisting of either resisted or unresisted sprints. 24 of the original 27 participants could later be included for statistical analysis. During intervention the TAU group performed the regular team training with no additional stimuli from the researchers. Anthropometrics, sprint, acceleration and jump performance testing was tested pre- and post-training intervention. Results The four-week training intervention resulted in significant improvements of sprint- and acceleration for the RST-group. The improvements were 3,8% (±0.05) in T30, 4,2% (±0.06) in T20, 5,7% (±0.06) in T10, and 7,9% (±0.06) in the T5. The RST and UST groups also had significant improvements in both vertical and horizontal jump performance. Further there were several significant between group changes in both sprint and jump performance favoring the RST group over both the UST and TAU groups. Conclusion The conclusions are that in this population a very heavy RST regimen elicits improvements in sprint and acceleration performance whilst a UST regimen does not. Further, both the RST- and UST- training regimens elicit improvements in both vertical and horizontal jump performance. The improvements of the present study follow the pattern of previous studies in the field indicating a greater horizontal force generating ability. However, the improvements in the present study are larger than previously seen, indicating that this type of training might be extra beneficial to enhance sprint and jump performance in late pubertal adolescent athletes. The findings of the present study also contradict the typical recommendations of using light resistance loads (i.e. the 10% rule) when it comes to RST. Heavier loads, as in this case 103,5% of body weight on average, can indeed be used to produce sprint and acceleration gains in a late pubertal adolescent athlete population. The improvement in these short sprints (5-30m) versus the eventual performance decrease in longer sprints 40-70m (e.g. due to less effective maximal velocity phase) is a trade off which logically should be worthwhile for team sport athletes.
Abstrakt Syfte Det huvudsakliga syftet med denna studie var att undersöka och jämföra effekterna av väldigt tungt belastad sprintträning och obelastad sprintträning på sprint-, acceleration och hopprestation hos unga fotbollsspelare i sena tonåren som ligger på en mognadsgrad av ”mid- post-PHV” samt >95% PAH. Metod Totalt 27 fotbollsspelare rekryterades som frivilliga deltagare. Deltagarna hade ingen tidigare erfarenhet av belastad sprintträning. Deltagarna blev slumpmässigt indelade till antingen den belastade (RST) eller den obelastade (UST) träningsgruppen. Dock skedde grupperingen med deltagarnas kraft- hastighetsprofilering som bas, då grupperna blev matchade efter denna. Kontrollgruppen (TAU n=8) matchades med experimentgrupperna efter ålder och antropometri. Träningen bestod av väldigt tungt belastad eller obelastad sprintträning och utfördes två gånger i veckan under fyra veckor. 24 av de initialt 27 deltagarna kunde inkluderas för vidare analys. Under interventionen genomförde TAU den vanliga lagträningen utan ytterligare träningsstimuli från forskarna. Antropometri, sprint, acceleration och hopprestation testades före respektive efter interventionen. Resultat Den fyra veckor långa träningsinterventionen resulterade i signifikanta förbättringar i sprint och acceleration för RST-gruppen. Förbättringarna var 3,8% (±0.05) i T30, 4,2% (±0.06) i T20, 5,7% (±0.06) i T10, och 7,9% (±0.06) i T5. RST och UST grupperna hade också signifikanta förbättringar i både vertikal och horisontell hopprestation. Vidare fanns det flera signifikanta mellangruppsskillnader i både sprint- och hopprestation till fördel för RST gruppen över både UST och TAU grupperna. Konklusion Konklusionen är att ett väldigt tungt RST-träningsprogram framkallar signifikanta förbättringar i både sprint, acceleration och hopprestation medan ett UST-träningsprogram inte gör det. Vidare kan konkluderas att både ett RST- och ett UST-träningsprogram signifikant förbättrar både vertikal och horisontell hopprestationen. Förbättringarna följer mönstret från tidigare studier på området och indikerar en större horisontell kraftproduktion. Dock är förbättringarna större än vad som tidigare observerats vilket indikerar att denna typ av träning kan vara extra förtjänstfull för denna population. Resultaten motsäger även den typiska rekommendationen kring lätta vikter (dvs. 10% regeln) vid belastad sprintträning. Tyngre belastning, som i detta fall i genomsnitt 103,5% av kroppsvikten, kan användas för att producera sprint- och accelerationsförbättringar i denna population. Förbättringen av denna typ av korta sprinter (5-30m) gentemot den eventuella prestationsförsämringen i längre sprinter (40-70m) torde vara ett byte som är värt att göra för lagidrottare.

Thesis (M.Sc.)--York University, 2008. Graduate Programme in Kinesiology and Health Science.
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Dissertação de Mestrado em Treino Desportivo para Crianças e Jovens apresentada à Faculdade de Ciências do Desporto e Educação Física
Soccer is one of the most popular sports in the world, and there are a lots of training method introduced to improve players’ performance, and small-side game (SSG) was one of the reliable method as it is highly modifiable and a good method to simulate real match situation. The aim of present study was to investigate the differences of activity pattern between different age groups during small-sided game (SSG) by investigating the change of heart rate (HR), speed and distance covered and see if there was any difference to between ages to provide feedback for the coaches which assist their SSG training plan. In present study, there were no significant difference (p>0.05) between U-12 and U-13, U-12 and U-14, U-13 and U-14 in HR, no significant difference (p>0.05) between U13 and U-14 in distance covered, and no significant difference (p>0.05) between U-12 and U-13, U-12 and U-14, U-13 and U-14 in speed. To conclude the finding of present study, present study discovers that during a seven-a-side SSG match, there were no significant differences between U-12, U-13, and U-14 players in HR, distance covered and speed which suggest that U-12, U-13 and U-14 have similar activity pattern during a seven-a-side SSG.Soccer is one of the most played sports around the world, from the report of FIFA, the 2014 FIFA World Cup have 32 teams, and there are over 265 million soccer players around the world which shows soccer is a very popular team sport in the world. As a team sport, soccer players could develop a complex, open system during the match which constituted of many degrees of freedom that result from the variety of possible interactions among system components (Duarte et al., 2012; Mendez-Villanueva et al., 2013). In these systems, they consist lots of high speed, intensive activities. During a match, soccer players must cover distance by walking, jogging, running, and sprinting. The speed intensity is dependent upon a variety of factors, including training level, team playing style and ability to maintain possession, player positions, tactical situations, period of competition, and the intensity can reach to the anaerobic threshold, but 90% of the energy used was produced by the aerobic system (Di Salvo, 2012; Radzimisnski et al., 2013). The overall activity pattern of soccer consists intermittent high-intensity type and, in average, high-speed activity accounts for approximately 8 % of the total distance covered during match-play (Gregson, 2010; Mukherjee & Chia, 2013; Nicholas et al., 1999). To develop an elite soccer team, players must go through the training from a young age and learn all types of soccer motor skills and master them when they are growing up. Since soccer development has gone through a long period of time, modern soccer training evolved towards integrated types of physical training and many types of training method to suit the need of competitive demands and technical skills development. Among these types of training methods, small-sided game (SSG) is one of the most popular training method and proved to be a reliable, effective training.
Soccer is one of the most popular sports in the world, and there are a lots of training method introduced to improve players’ performance, and small-side game (SSG) was one of the reliable method as it is highly modifiable and a good method to simulate real match situation. The aim of present study was to investigate the differences of activity pattern between different age groups during small-sided game (SSG) by investigating the change of heart rate (HR), speed and distance covered and see if there was any difference to between ages to provide feedback for the coaches which assist their SSG training plan. In present study, there were no significant difference (p>0.05) between U-12 and U-13, U-12 and U-14, U-13 and U-14 in HR, no significant difference (p>0.05) between U13 and U-14 in distance covered, and no significant difference (p>0.05) between U-12 and U-13, U-12 and U-14, U-13 and U-14 in speed. To conclude the finding of present study, present study discovers that during a seven-a-side SSG match, there were no significant differences between U-12, U-13, and U-14 players in HR, distance covered and speed which suggest that U-12, U-13 and U-14 have similar activity pattern during a seven-a-side SSG.Soccer is one of the most played sports around the world, from the report of FIFA, the 2014 FIFA World Cup have 32 teams, and there are over 265 million soccer players around the world which shows soccer is a very popular team sport in the world. As a team sport, soccer players could develop a complex, open system during the match which constituted of many degrees of freedom that result from the variety of possible interactions among system components (Duarte et al., 2012; Mendez-Villanueva et al., 2013). In these systems, they consist lots of high speed, intensive activities. During a match, soccer players must cover distance by walking, jogging, running, and sprinting. The speed intensity is dependent upon a variety of factors, including training level, team playing style and ability to maintain possession, player positions, tactical situations, period of competition, and the intensity can reach to the anaerobic threshold, but 90% of the energy used was produced by the aerobic system (Di Salvo, 2012; Radzimisnski et al., 2013). The overall activity pattern of soccer consists intermittent high-intensity type and, in average, high-speed activity accounts for approximately 8 % of the total distance covered during match-play (Gregson, 2010; Mukherjee & Chia, 2013; Nicholas et al., 1999). To develop an elite soccer team, players must go through the training from a young age and learn all types of soccer motor skills and master them when they are growing up. Since soccer development has gone through a long period of time, modern soccer training evolved towards integrated types of physical training and many types of training method to suit the need of competitive demands and technical skills development. Among these types of training methods, small-sided game (SSG) is one of the most popular training method and proved to be a reliable, effective training.

Dissertação de Mestrado Internacional em Análise da Performance Desportiva
The aim of this study is to verify if differencial learning can improve technical skill pass more than the traditional training in youth football and futsal players. The sample was composed by 27 young Portuguese football players from Under 11 age group (U11: n=27, age: 10.0 ± 0.39) and 17 young Portuguese futsal players (U11: n=17, age: 9.27 ± 1.03). Each team was divided into 2 groups (control group and experimental group), in total 4 groups were made, two control and two experimental groups. The intervention time was around 2 months, and only experimental groups had an interventional program based on differential learning. The intervention was founded on analytic exercises and a small-side-games. Both groups performed the Loughborough Football Passing Test and the Creative Behaviour Assessment in Team Sports (CBATS) to assess the pass skills. The results of the Loughborough Football Passing Test showed that all 4 groups improved from the pre to the post test, however, a higher improve was presented in the experimental groups in football (-1,7; ± 1,3, possibly -ive) and socfutsal (-0,4; ±1,2, likely) teams when comparing with the control groups. Regarding to game related creative behaviour the results showed that the experimental group of the socfutsal team improves more in the versatility (0,6; ±0,6, likely + ive) and in the fails (0,5; ±0,5, likely – ive), on the other hand the fluency was stressed in the football team (0,5; ±0,9, possibly + ive). Comparing the two teams, the training intervention seems to be more effective in the football team. This study demonstrated that a differential learning intervention can provide an improvement in the performance of the pass technique in football and futsal players.
O objetivo deste estudo foi verificar se a aprendizagem diferencial pode melhorar a capacidade técnica do passe quando comparado a um modelo de aprendizagem mais tradicional em jovens jogadores de futebol e futsal. A amostra era composta por 27 jovens jogadores portugueses de futebol no escalão sub-11 (Sub11: n=27, idade: 10.0 ± 0.39) e 17 jovens jogadores portugueses de futsal (Sub11: n=17, idade: 9.27 ± 1.03). cada equipa foi dividida em dois grupos, formando assim o grupo controlo e o grupo experimental. A intervenção foi de cerca de 2 meses e apenas os grupos experimentais participavam no programa de intervenção. O programa era baseado em na aprendizagem diferencial, utilizando exercícios analíticos e jogo reduzido. Toda a amostra executou o mesmo teste para avaliar o passe, o Loughborough Football Passing Test e um jogo reduzido para avaliar a criatividade. Os resultados do Loughborough Football Passing Test demostram que todos os grupos melhoraram, tendo melhor resultados o grupo experimental de futebol (-1,7; ± 1,3, possibly-ive) e socfutsal (-0,4; ±1,2, likely) quando comparado com os grupos de controlo do pré para o pós-teste. Relativamente á criatividade os resultados mostram que o grupo experimental melhora mais na versatilidade na equipa de futsal (0,6; ±0,6, likely +ive) e nas falhas (-0,5; ±0,5, likely –ive) e fluência (0,5; ±0,9, possibly +ive) na equipa de futebol. Mostrando assim que o programa de treino ajuda no aumento da performance. No LSPT ambos os grupos experimentais (futebol e futsal) melhoraram comparativamente aos grupos de controlo. Comparando as duas equipas, o programa de treino parece ser mais efetivo na equipa de futebol. Este estudo demostra que a aprendizagem diferencial pode providenciar um aumento na performance relacionada á técnica do passe em jogadores de futebol e futsal.

Na presente tese procura-se fornecer demonstrações empíricas e orientações pedagógicas para a compreensão e modelação do contexto formal do jogo de futebol em relação às caraterísticas dos jogadores, indagando se os constrangimentos estruturais e funcionais da competição (superfície do campo, formato de jogo, e escalão etário) promovem assimetrias na performance física, técnica e tática dos jovens jogadores. Ainda há pouca evidência científica sobre as mudanças produzidas no desempenho dos jogadores e equipas devido ao efeito dos constrangimentos estruturais e funcionais da competição infanto-juvenil. Assim, é difícil justificar se jogos de futebol das competições infanto-juvenis são realizados em condições de jogo adaptadas ao nível de habilidade e idade dos jogadores. Por conseguinte, pretendeu-se perceber que tipo de formatos de jogo são utilizados nos campeonatos infanto-juvenis e como os respetivos formatos se correlacionam com a idade dos jogadores. Para tal, realizou-se um estudo com recurso a um teste de independência de Qui-Quadrado e um coeficiente de correlação ordinal de Spearman para correlacionar o escalão etário com os diferentes formatos de jogo utilizados nas competições infanto-juvenis. Posteriormente, considerando os formatos de jogo (5v5; 7v7; 9v9; e 11v11) e o tipo de superfícies de campo (relva natural; relva artificial; e terra batida) que são utilizados nos campeonatos infanto-juvenis, desenvolveram-se mais quatro estudos para indagar: (i) o efeito da superfície do campo na atividade locomotora e no desempenho técnico de jovens futebolistas; (ii) o efeito da superfície do campo no posicionamento e deslocamento de jovens futebolistas; (iii) o efeito do formato do jogo e escalão etário na atividade locomotora de jovens futebolistas; (iv) a influência dos formatos de jogo no posicionamento e deslocamento de jovens futebolistas durante o jogo. Os resultados encontrados permitiram constatar que os formatos de jogo mais utilizados na Europa (Estudo I) são o 5v5, 7v7, 9v9, e 11v11 mostrando uma correlação significativa com os escalões etários de U8, U10, U12, e U14 respetivamente (χ2 (63) = 477,724; p <0,001), com um coeficiente de correlação de Spearman de (0.852). Os estudos (ii) e (iii) evidenciaram um efeito significativo da superfície do campo na atividade locomotora (p < 0.05), no desempenho técnico (p < 0.001) e no posicionamento (p < 0.001) e deslocamento (p < 0.05) dos jovens futebolistas. Relativamente aos estudos (iv) e (v) os resultados demonstraram que o formato de jogo e o escalão etário influenciam significativamente a atividade locomotora (p < 0.001) e o posicionamento (p < 0.001) e deslocamento (p < 0.001) dos jovens futebolistas. Podemos afirmar que a superfície de relva natural induz a diminuição da atividade locomotora dos futebolistas enquanto a relva artificial reflete maior atividade locomotora assim como um estilo de jogo mais estruturado do ponto de vista tático; a superfície de terra batida promove o insucesso na execução das ações técnicas enquanto a relva artificial promove o aumento de ações bem-sucedidas. Também podemos argumentar que o formato de 11v11 promove o aumento significativo da atividade locomotora e maior estabilidade na variabilidade do posicionamento e deslocamento dos futebolistas; os formatos de 5v5 e 7v7 induzem menor atividade locomotora assim como o aumento de movimentos e ações imprevisíveis. Também identificamos que em idades entre os 8-10 anos os futebolistas tendem a realizar movimentos longitudinais e laterais de maior amplitude comparativamente a futebolistas com 12-14 anos. O conhecimento mais preciso sobre as adaptações promovidas pelas superfícies do campo, formatos de jogo e escalões etários pode contribuir para que os treinadores utilizem ferramentas mais apropriadas no processo de formação de futebolistas. Além disso, pode ajudar os treinadores e instituições reguladoras nacionais a implementarem condições adequadas de prática em que as exigências do jogo sejam adequadas à idade e às caraterísticas desenvolvimentais dos jovens praticantes.PALAVRAS-CHAVE: FUTEBOL, DESEMPENHO FÍSICO E TÉCNICO-TÁTICO, CONSTRANGIMENTOS DE JOGO, FORMATOS DE JOGO, SUPERFÍCIE DE CAMPO, ANÁLISE DA PERFORMANCE
This thesis aims to provide empirical evidence and pedagogical guidelines for understanding and modelling the formal context of soccer matches. More specifically, it aims to investigate whether the structural and functional constraints of the competition induce asymmetries in the physical, technical and tactical performance of youth players. The lack of scientific evidence about the effect of game constraints (i.e. pitch surface, game format and age-group) on performance of young players, reflects many doubts about whether the competitive design that are being used in youth soccer are suitable to the characteristics and capacity of the participants. Thus, we proposed to understand what kind of game formats are used in the youth championships and how the respective formats correlate with the age of the players. For this, a study was performed using a Chi-Square independence test and Spearman´s ordinal correlation coefficient to correlate the age-group with the formats. Posteriorly, considering the game formats (5v5; 7v7; 9v9; and 11v11) and the type of pitch surfaces (natural turf; artificial turf; and dirt field) that are being used in the youth championships, four studies were carried out to investigate: (i) the effect of the pitch surface on running activity and technical performance of young soccer players; (ii) the effect of the pitch surface on the positioning and displacement of young players; (iii) the effect of the game format and age-group on running activity of young players; (iv) the influence of the game formats on the positioning and displacement of young soccer players during match-play. The following statistical procedures were used: Kolmogorov-Smirnov and Shapiro-Wilks parametric tests to test adherence to data normality; two-way analysis of variance (ANOVA) with repeated measures to quantify differences in means of dependent variables; Mauchly´s test of sphericity was performed to verify any violations of sphericity, which were corrected through the Greenhouse-Geisser adjustment; effect sizes were reported as partial eta squared (η2) obtained with the ANOVAs. The results showed that the most widely used game formats in Europe (Study I) are the 5v5, 7v7, 9v9, and 11v11, showing a significant correlation with the U8, U10, U12, and U14 age-groups, respectively (χ2 (63) = 477,724, p < 0.001), with a Spearman correlation coefficient of (0.852). Studies (ii) and (iii) showed a significant effect of pitch surface on running activity (p < 0.05), in the technical performance (p <0.001) and the positioning (p < 0.001) and displacement (p < 0.05) of young soccer players. The results of the studies (iv) and (v) showed that the game format and the age-group significantly influence running activity (p < 0.001) and the positioning (p < 0.001) and displacement (p < 0.001) of the young soccer players. Thus, we can argue that the natural turf surface induces a decrease in the players´ running activity while the artificial turf reflects greater running activity as well as a more tactically structured game style. Additionally, the dirt field surface promotes failure in the execution of technical actions while the artificial turf promotes the increase of successful actions. We can also argue that the 11v11 game format promotes a significant increase in running activity and greater stability in the positioning and displacement variability of the players. Finally, the 5v5 and 7v7 formats induce less running activity as well as the increase unintentional movements and actions. We also identified that the players of 8-10 years tend to perform longitudinal and lateral movements of greater amplitude compared to soccer players with 12-14 years. The most accurate knowledge about the adaptations induced by pitch surfaces, game formats and age-groups can contribute to the coaches use the most appropriate tools in the process of the players´ development. Moreover, can help the coaches and national bodies to implement appropriate conditions of practice in which the requirements of the game are appropriate to the age and characteristics of the players.

Na presente tese procura-se fornecer demonstrações empíricas e orientações pedagógicas para a compreensão e modelação do contexto formal do jogo de futebol em relação às caraterísticas dos jogadores, indagando se os constrangimentos estruturais e funcionais da competição (superfície do campo, formato de jogo, e escalão etário) promovem assimetrias na performance física, técnica e tática dos jovens jogadores. Ainda há pouca evidência científica sobre as mudanças produzidas no desempenho dos jogadores e equipas devido ao efeito dos constrangimentos estruturais e funcionais da competição infanto-juvenil. Assim, é difícil justificar se jogos de futebol das competições infanto-juvenis são realizados em condições de jogo adaptadas ao nível de habilidade e idade dos jogadores. Por conseguinte, pretendeu-se perceber que tipo de formatos de jogo são utilizados nos campeonatos infanto-juvenis e como os respetivos formatos se correlacionam com a idade dos jogadores. Para tal, realizou-se um estudo com recurso a um teste de independência de Qui-Quadrado e um coeficiente de correlação ordinal de Spearman para correlacionar o escalão etário com os diferentes formatos de jogo utilizados nas competições infanto-juvenis. Posteriormente, considerando os formatos de jogo (5v5; 7v7; 9v9; e 11v11) e o tipo de superfícies de campo (relva natural; relva artificial; e terra batida) que são utilizados nos campeonatos infanto-juvenis, desenvolveram-se mais quatro estudos para indagar: (i) o efeito da superfície do campo na atividade locomotora e no desempenho técnico de jovens futebolistas; (ii) o efeito da superfície do campo no posicionamento e deslocamento de jovens futebolistas; (iii) o efeito do formato do jogo e escalão etário na atividade locomotora de jovens futebolistas; (iv) a influência dos formatos de jogo no posicionamento e deslocamento de jovens futebolistas durante o jogo. Os resultados encontrados permitiram constatar que os formatos de jogo mais utilizados na Europa (Estudo I) são o 5v5, 7v7, 9v9, e 11v11 mostrando uma correlação significativa com os escalões etários de U8, U10, U12, e U14 respetivamente (χ2 (63) = 477,724; p <0,001), com um coeficiente de correlação de Spearman de (0.852). Os estudos (ii) e (iii) evidenciaram um efeito significativo da superfície do campo na atividade locomotora (p < 0.05), no desempenho técnico (p < 0.001) e no posicionamento (p < 0.001) e deslocamento (p < 0.05) dos jovens futebolistas. Relativamente aos estudos (iv) e (v) os resultados demonstraram que o formato de jogo e o escalão etário influenciam significativamente a atividade locomotora (p < 0.001) e o posicionamento (p < 0.001) e deslocamento (p < 0.001) dos jovens futebolistas. Podemos afirmar que a superfície de relva natural induz a diminuição da atividade locomotora dos futebolistas enquanto a relva artificial reflete maior atividade locomotora assim como um estilo de jogo mais estruturado do ponto de vista tático; a superfície de terra batida promove o insucesso na execução das ações técnicas enquanto a relva artificial promove o aumento de ações bem-sucedidas. Também podemos argumentar que o formato de 11v11 promove o aumento significativo da atividade locomotora e maior estabilidade na variabilidade do posicionamento e deslocamento dos futebolistas; os formatos de 5v5 e 7v7 induzem menor atividade locomotora assim como o aumento de movimentos e ações imprevisíveis. Também identificamos que em idades entre os 8-10 anos os futebolistas tendem a realizar movimentos longitudinais e laterais de maior amplitude comparativamente a futebolistas com 12-14 anos. O conhecimento mais preciso sobre as adaptações promovidas pelas superfícies do campo, formatos de jogo e escalões etários pode contribuir para que os treinadores utilizem ferramentas mais apropriadas no processo de formação de futebolistas. Além disso, pode ajudar os treinadores e instituições reguladoras nacionais a implementarem condições adequadas de prática em que as exigências do jogo sejam adequadas à idade e às caraterísticas desenvolvimentais dos jovens praticantes. PALAVRAS-CHAVE: FUTEBOL, DESEMPENHO FÍSICO E TÉCNICO-TÁTICO, CONSTRANGIMENTOS DE JOGO, FORMATOS DE JOGO, SUPERFÍCIE DE CAMPO, ANÁLISE DA PERFORMANCE
This thesis aims to provide empirical evidence and pedagogical guidelines for understanding and modelling the formal context of soccer matches. More specifically, it aims to investigate whether the structural and functional constraints of the competition induce asymmetries in the physical, technical and tactical performance of youth players. The lack of scientific evidence about the effect of game constraints (i.e. pitch surface, game format and age-group) on performance of young players, reflects many doubts about whether the competitive design that are being used in youth soccer are suitable to the characteristics and capacity of the participants. Thus, we proposed to understand what kind of game formats are used in the youth championships and how the respective formats correlate with the age of the players. For this, a study was performed using a Chi-Square independence test and Spearman´s ordinal correlation coefficient to correlate the age-group with the formats. Posteriorly, considering the game formats (5v5; 7v7; 9v9; and 11v11) and the type of pitch surfaces (natural turf; artificial turf; and dirt field) that are being used in the youth championships, four studies were carried out to investigate: (i) the effect of the pitch surface on running activity and technical performance of young soccer players; (ii) the effect of the pitch surface on the positioning and displacement of young players; (iii) the effect of the game format and age-group on running activity of young players; (iv) the influence of the game formats on the positioning and displacement of young soccer players during match-play. The following statistical procedures were used: Kolmogorov-Smirnov and Shapiro-Wilks parametric tests to test adherence to data normality; two-way analysis of variance (ANOVA) with repeated measures to quantify differences in means of dependent variables; Mauchly´s test of sphericity was performed to verify any violations of sphericity, which were corrected through the Greenhouse-Geisser adjustment; effect sizes were reported as partial eta squared (η2) obtained with the ANOVAs. The results showed that the most widely used game formats in Europe (Study I) are the 5v5, 7v7, 9v9, and 11v11, showing a significant correlation with the U8, U10, U12, and U14 age-groups, respectively (χ2 (63) = 477,724, p < 0.001), with a Spearman correlation coefficient of (0.852). Studies (ii) and (iii) showed a significant effect of pitch surface on running activity (p < 0.05), in the technical performance (p <0.001) and the positioning (p < 0.001) and displacement (p < 0.05) of young soccer players. The results of the studies (iv) and (v) showed that the game format and the age-group significantly influence running activity (p < 0.001) and the positioning (p < 0.001) and displacement (p < 0.001) of the young soccer players. Thus, we can argue that the natural turf surface induces a decrease in the players´ running activity while the artificial turf reflects greater running activity as well as a more tactically structured game style. Additionally, the dirt field surface promotes failure in the execution of technical actions while the artificial turf promotes the increase of successful actions. We can also argue that the 11v11 game format promotes a significant increase in running activity and greater stability in the positioning and displacement variability of the players. Finally, the 5v5 and 7v7 formats induce less running activity as well as the increase unintentional movements and actions. We also identified that the players of 8-10 years tend to perform longitudinal and lateral movements of greater amplitude compared to soccer players with 12-14 years. The most accurate knowledge about the adaptations induced by pitch surfaces, game formats and age-groups can contribute to the coaches use the most appropriate tools in the process of the players´ development. Moreover, can help the coaches and national bodies to implement appropriate conditions of practice in which the requirements of the game are appropriate to the age and characteristics of the players.

ABSTRACT Common lower extremity injuries in female high school soccer players in Johannesburg east district Mtshali P.T.S. Background and purpose of research As the number of females participating in sports has increased, so has the necessity of understanding the effect of female growth and development in participation, athletic ability and injury patterns. Soccer is one of the sports where South Africa has seen an increase of youth and adult females’ participation. Aim: To establish the prevalence of and extrinsic risk factors contributing to injuries in the lower extremity in female high school soccer players in the Johannesburg east district. Method: A retrospective descriptive questionnaire – based study of 103 first team high school female soccer players in the Johannesburg east district was conducted. This was to determine point and one year prevalence of injuries, profile of injuries that affect female soccer players, associations between injuries and player position, age, use of equipment, frequency of play, and training duration and also to identify possible risk factors that contribute to injuries. Results: The one year prevalence of injured players was 46.1% and point prevalence was 37.8%. Knee injuries (18.6%) and ankle injuries (17.6%) were reported for one year prevalence and for point prevalence knee injuries were 13.3% and ankle injuries 18.9%. An extended duration of skills (p=0.0001) and fitness (p=0.02) training in this population reduced the likelihood of incurring an injury and the older (p=0.01) the players, the more chances of sustaining injuries. The players who wore shin guards were less prone to shin/leg injuries (p=0.01) and the relative odds were 0.35 (CI 0.16-0.79). The midfielders had more foot and toe injuries (p = 0.05). Starting age (p=0.78), frequency of play (p=0.83) wearing of shoes (p=0.54) and stretching had no influence on injury. Conclusion: The knee and ankle were the main locations of injury with defenders and midfielders mostly being injured. The increased duration of training for both skills and fitness and not wearing shin guards are risk factors for injury in female soccer players in high school.

This study aimed to compare the acute effects of two independent warm-up (WU) protocols, neuromuscular warm-up (NMWU) and standardized soccer warm-up (STWU), on three soccer-specific performance tests in adolescent male and female soccer players. Substantial evidence exists of NMWU programs reducing Anterior Cruciate Ligament (ACL) injuries, particularly in soccer. Regardless of this reduced risk of injury, NMWU program adherence is low. Enhanced athletic performance has been reported to encourage consistent WU adherence more effectively than injury risk, especially in youth athletes. Therefore this study compared the effects of a NMWU and a STWU on physical performance in youth soccer players to encourage adherence and implementation. Following familiarization with a locally developed NMWU, 35 (11 female, 24 male) student-athletes (mean age: 14.7 yrs) from two high school-based soccer academies completed four sessions over a two week period evaluating the effects of WU on three soccer specific performance tests. Performance tests included T-test (agility), vertical jump (Peak Power Output), and 20-m sprint (acceleration and speed). The first week of testing consisted of NMWU familiarization, Yo-Yo Intermittent Recovery Test Level 1, and the collection of physical characteristics. The second week of testing consisted of two testing sessions, WU protocols were randomly assigned to the testing sessions ahead of time (session 1: STWU; session 2: NMWU) and were completed at the beginning of the session prior to testing. A series of five two-tailed repeated measures ANOVA were conducted to determine significant differences in WU means. The overall group demonstrated a significant increase in Peak Power Output (p=0.001) and agility (p=0.016) following the STWU compared to the NMWU. Neither WU demonstrated a measurable effect on 5m,10m, and 20m times. The findings of this research may have been influenced by the single use of the NMWU which may have limited the NMWU potential to enhance the three soccer-related performance tests. In order to explore the effectiveness of NMWU on performance enhancement as a means of improving its adherence in youth players, further research implementing NMWU over an extended period of weeks or months should be carried out, consistent with studies demonstrating NMWU impact on ACL injury risk in youth and adults.
Graduate

碩士
中國文化大學
體育學系運動教練碩士班
98
Purpose: Three different aerobic fitness tests applied on youth soccer players. Performances of these three fitness tests are analyzed individually by comparing each correlation with the VO2max value. We try to discover the most valid and suitable field test for coaches to evaluate the aerobic capacity of youth soccer players. Methods: 14 volunteers from National Sang Chung senior high school (age 17±1.2 year old；height 172.4±6.4 cm；weight 65.8±6.3 kg) took part in the study during post season, completed the maximal oxygen uptake test with Bruce protocol at the laboratory over the period of a week. Three field tests were completed: the 12 min Cooper test, the 20m multistage shuttle run test (the beep test) and the Yo-Yo intermittent recovery level 2 test, separately over a two-week period. The subjects’ performances data gathered would be compared with VO2max by conducting the Pearson Product Moment Correlation way, to find the most closely related test. Results: Test-retest reproducibility of these three field tests was discovered (12 mins cooper test, ICC = .78；beep test, ICC = .70；Yo-Yo IR2 test, ICC = .69). The highest correlation between 12 min Cooper test performance and VO2max was found( r = .60, p < .05), subsequently the the Yo-Yo IR2 test ( r = .47, p > .05), and lastly the beep test ( r = 0.22, p > 0.05). Conclusion: 12 mins Cooper test has the ability to evaluat youth soccer player’s aerobic capacity from post-season, and stronger accuracy of estimating VO2max. The further researches about discovering the reason, for the lower correlation with VO2max of both the Beep test and the Yo-Yo IR2 test, are needed.

碩士
正修科技大學
休閒與運動管理所
105
Purposes: The purpose of this study was to investigate the effect of core strength training on the special skill of male adolescent soccer players. Methods: Subject to researchers currently teaches at the Kaohsiung City as a state within a football player as the main subject, ball players with no less than 4 years of age, a total of 20. The mean age of the control group (n = 12) was 14.16 ± .57 years, with a height of 158.08 ± 10.42 cm and a body weight of 47.16 ± 9.06 kg. The average age of the control group (n = 8) was 15.37 ± .74 years, height 170.00 ± 5.90 cm, ± 8.58 kg are male players. And the implementation of eight weeks of core training, 3 times a week, each time 30 minutes, and before and after the implementation of its special technology: 1. Soccer fixed point kick; 2. 20 meters S-type ball; Throw away. Special physical fitness: 1.30 meters rushed; 2. standing long jump; 3. a minute knees sit-ups; 4. sitting posture front bend; 5.100 meters run; 6.12 minutes to run. Results: 1. Special skill: "standing long jump", "sitting in front of the bend", "100 meters", "30 meters sprint" experimental group was significantly better than the control group; 2. Special technology: "20 meters S disk The experimental group was significantly better than the control group. Conclusion: 1. Core strength training for men and adolescents soccer players with a significant physical fitness has improved significantly. 2. Core strength training for men and adolescent football players with a significant improvement in special technology.

Submitted to the Faculty of Health Science in partial compliance with the requirements for the Master’s Degree in Technology : Chiropractic, Department of Chiropractic,Durban University Of Technology, Durban. South Africa, 2015.
Introduction: Participation of young females in soccer has started to increase in the past few years. Females participating in soccer are more vulnerable to injuries than males due to the nature of the sport especially because the sport is characterised as a vigorous, high intensity, intermittent ball and contact activity. Objective: This study sought to determine the epidemiology of injuries in high school female soccer players in the eThekwini district. Method: A quantitative approach using a cross sectional survey was used to determine the epidemiology of injuries in female high school soccer players in the eThekwini district. One-hundred-and-ninety-seven female high school soccer players, between the ages of 14 to 19 years who have played soccer for at least one season, from 27 female high schools in the eThekwini district were invited to participate. A self-administered questionnaire was used to determine the demographic profile of the players and the reported prevalence of injuries in the soccer players. The study also determined the profile of soccer related injuries, management of injuries, identified risk factors for injury, and compared injuries occurring during training and during matches. Results: Out of a total of 85 respondents only 31 sustained injuries. The injury prevalence for the season was 36.5%. Only 61 injuries (71.8%) were reported by the injured players. The rate of injury was 90 per 1000 athlete exposure hours during the season. Only two female players reported the five injuries while all 29 female players sustained at least one injury. The defenders (31.7%) and midfielders (28.6%) sustained the most injuries. Most injuries reported were contact in nature (12.9%). More injuries occurred during training (12.9%) rather than during matches (8.2%). The lower extremity (77.8%) was injured more than the upper extremity (22.2%). The knee (22.2%) and ankle (15.9%) were the most frequently injured body parts. Muscle injury (23.5%) was the most commonly reported followed by bruising (10.6%). Conclusion: Prevalence of injuries was high in the cohort studied. The lower limb, specifically the knee and ankle were most commonly injured. Muscle injury and bruising were the most common injury affecting the lower extremity. It is recommended that the study be extended to a larger cohort of school children.

碩士
國立屏東教育大學
體育學系碩士班
101
The main purpose of the study was to explore the difference of the youth soccer players team culture between aboriginal and non-aboriginal schools in Pingtung and sources of sport-confidence . This study used questionnaires with the tools of team culture scale and sport-confidence scale. Study objects were junior high school soccer team players with total of 166 valid samples (Aboriginal schools-71 participants,non-aboriginal schools-95 participants); Data were the statistical software package SPSS For Windows 12.0 for data analysis, statistical analysis included descriptive statistics、one-way MANOVA analysis、Pearson product-moment correlation analysis and canonical correlation analysis. The results were as follows: 1. Different grades of youth soccer players variables in team culture, “Obedience Orientation”of ninth grade was higher than seventh grade;“Championship Orientation”of aboriginal school was higher than non-aboriginal school. 2. Different grades of youth soccer players variables in sport-confidence,“ vicarious experience” 、 “situation advantage” 、 “mastery technic”and “showing ability”aspects of ninth grade were higher than seventh grade; “situation advantage”aspect of aboriginal school was higher than non-aboriginal school;“mastery technic”aspect of non-aboriginal school was higher than aboriginal school. 3. The canonical correlation between team culture and sources of sport-confidence was significant. Based on the results,suggestions for future researches were discussed and proposed.

Background: With the aim of professional status and sporting success, selection processes and talent identification in youth players are common in football clubs and national teams. Football requiring different types of abilities, standing out in certain abilities can be important in the selection process for national teams. Physical abilities including maximal power can differ between players in the same age group due to growth and maturation and might therefore be important factors in the selection process. Previous studies have mentioned maximal power as one of many performance indicators for football performance. However, few studies have investigated its importance regarding youth players selected or not selected for the national team. Aim: The study was designed to measure and compare jump height and jump length in three different jump tests between youth soccer players selected or not selected for the national team. Methods: Twenty-two (n=22) players, eleven national players and eleven non-national players performed three different jump tests. The players were 17±2 years old from the club Halmstads BK, Halmstad. The study was an observational crosssectional study that was designed to measure and compare jump height and jump length in three different jump tests between youth soccer players selected or not selected for the national team. The jump tests that were used in the present study was Countermovement Jump (CMJ), Abalakov Jump (AJ) and Standing Long Jump (SLJ). Mean scores for the tests in both groups were analyzed and compared and the criterion level for significance was set to p ≤ 0.05. Results: The results showed a significant difference between the groups regarding jump height in CMJ (p=0.013) and in AJ (p=0.010). No significant difference was found regarding jump length in SLJ (p=0.084). Conclusion: The findings of this study showed a significant difference in Countermovement Jump (CMJ) and Abalakov Jump (AJ) between national players (NP) and non-national players (NNP). The study found no significant difference between the groups in Standing Long Jump (SLJ). The results indicate the use of maximal power as a performance indicator and part of the selection of players to national teams. Anthropometric data (age, weight and height) was similar between the groups, therefore, other maturation and growth factors together with biological age are aspects that might have influenced the results. Future studies are suggested to investigate maturation status and its importance for maximal power in national players and non-national players.

M. Tech. Clinical Technology.
Soccer is the most popular sport in the world. Elite level soccer players cover about 10 km during a 90-minute game. Although running is the predominant activity in soccer, explosive movements such as sprinting, jumping and kicking are important for successful performance. The aims of this study were to determine the technical skill ability, aerobic and anaerobic fitness of the players; determine whether a relationship exists between the technical skill ability and aerobic and anaerobic fitness; and determine whether a relationship exists between team ranking order and these variables.

Abstract Aim was to investigate the effects of heavy resisted and unresisted sprint training protocols and see its effects on sprint time, vertical and horizontal jumping and sprint mechanics. Youth male soccer players [n=27] participated in this study, they were all individually assessed for the horizontal force-velocity profile using two unresisted sprints and load-velocity profile using four progressively resisted sprints (25%, 50%, 75% and 100% body mass). For all sprints an isotonic braking device was used. They also performed vertical and horizontal jumps, counter-movement jump (CMJ) was used for the former and standing long jump (SLJ) for the latter. They were put in three groups (RST: resisted sprint training; UST: unresisted sprint training and TAU: control group – “training as usual”). Athletes performed a 4-week training intervention (5x20m resisted sprint group; 8x20m unresisted sprint group) and were tested 7 days after completing their final training session. Only RST improved all sprint times (T30, T20, T10, T5) substantially (-4.2% to -7.9% in split times) and provided trivial or small changes in sprint mechanics. The small changes were seen in sprint mechanical parameters of RFmax, Pmax and F0. UST only showed trivial effects in those parameters, while TAU showed a small decrease in both Pmax and Vmax. Regarding the jumps, RST and UST both showed a small increase in standing long jump and a trivial effect in counter-movement jump, while TAU decreased in both. Main conclusion is that resisted sprinting has proven to be a worthwhile method to improve acceleration and sprint performance and can be used by practitioners across a wide array of sports. It also improved jumping performance and sprint mechanical outputs, which point toward an improvement in better application of force in a horizontal direction.

O objetivo do presente estudo foi identificar as variáveis notacionais e variáveis posicionais que se associam ao sucesso das equipas dos três escalões de formação (Sub-16, Sub-17 e Sub-19) em jogos reduzidos de futebol (5+GR vs. 5+GR). A amostra foi constituída por 36 jovens jogadores. Cada escalão foi dividido em duas equipas que jogaram 8 minutos. Para registo dos dados foi desenvolvido um sistema de observação constituído por variáveis notacionais ofensivas (simples e compostas) e defensivas, e por quatro variáveis posicionais coletivas (área de superfície, índice de dispersão, comprimento da equipa e largura da equipa) registadas no ataque e defesa. Os resultados do teste de Mann-Whitney demonstraram as variáveis Número de passes, Número de contatos com a bola, Ritmo de intervenção sobre a bola, Ritmo de transmissão da bola e o Número de passes/Número de jogadores intervenientes variam significativamente em função do sucesso das sequências ofensivas no escalão Sub-16. O teste ANOVA revelou que a variável posicional Comprimento da equipa está relacionada com o sucesso das sequências ofensivas nos três escalões etários. Ficou confirmado que o comportamento das equipas em campo e os fatores que influenciam o sucesso ofensivo e defensivo variam em função da idade e experiência dos praticantes.
The purpose of this study was to identify the notational variables and positional variables associated with the success of the teams of three age groups (U16, U17 and U19) in small-sided games (5 + GK vs. 5 + GK). The sample consisted of 36 young players. Each age group was divided into two teams that played 8 minutes. To record the data, an observation system was developed consisting of offensive (simple and compound) and defensive variables, and four collective positional variables (surface area, stretch index, team length and team width) registered in the attack and defense. The results of the Mann-Whitney test showed that the variables Number of passes, number of touches, rhythm of intervention on the ball, rhythm of transmission of the ball and number of passes / number of players involved vary significantly according on success of the offensive sequences at the U16 age group. The ANOVA test revealed that the positional variable Team length is related to the success of the offensive sequences in the three age groups. It was confirmed that the behaviour of the teams on the field and the factors that influence the offensive and defensive success vary according to the age and experience of the practitioners.