Journal articles on the topic 'Concentric and eccentric load'
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Merrigan, Justin J., James J. Tufano, Michael Falzone, and Margaret T. Jones. "Effectiveness of Accentuated Eccentric Loading: Contingent on Concentric Load." International Journal of Sports Physiology and Performance 16, no. 1 (January 1, 2021): 66–72. http://dx.doi.org/10.1123/ijspp.2019-0769.
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Purpose: To identify acute effects of a single accentuated eccentric loading (AEL) repetition on subsequent back-squat kinetics and kinematics with different concentric loads. Methods: Resistance-trained men (N = 21) participated in a counterbalanced crossover design and completed 4 protocols (sets × repetitions at eccentric/concentric) as follows: AEL65, 3 × 5 at 120%/65% 1-repetition maximum (1-RM); AEL80, 3 × 3 at 120%/80% 1-RM; TRA65, 3 × 5 at 65%/65% 1-RM; and TRA80, 3 × 3 at 80%/80% 1-RM. During AEL, weight releasers disengaged from the barbell after the eccentric phase of the first repetition and remained off for the remaining repetitions. All repetitions were performed on a force plate with linear position transducers attached to the barbell, from which eccentric and concentric peak and mean velocity, force, and power were derived. Results: Eccentric peak velocity (−0.076 [0.124] m·s−1; P = .01), concentric peak force (187.8 [284.4] N; P = .01), eccentric mean power (−145.2 [62.0] W; P = .03), and eccentric peak power (−328.6 [93.7] W; P < .01) during AEL65 were significantly greater than TRA65. When collapsed across repetitions, AEL65 resulted in slower eccentric velocity and power during repetition 1 but faster eccentric and concentric velocity and power in subsequent repetitions (P ≤ .04). When comparing AEL80 with TRA80, concentric peak force (133.8 [56.9] N; P = .03), eccentric mean power (−83.57 [38.0] W; P = .04), and eccentric peak power (−242.84 [67.3] W; P < .01) were enhanced. Conclusions: Including a single supramaximal eccentric phase of 120% 1-RM increased subsequent velocity and power with concentric loads of 65% 1-RM, but not 80% 1-RM. Therefore, AEL is sensitive to the magnitude of concentric loads, which requires a large relative difference to the eccentric load, and weight releasers may not need to be reloaded to induce performance enhancement.
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Taber, Christopher B., Jared R. Morris, John P. Wagle, and Justin J. Merrigan. "Accentuated Eccentric Loading in the Bench Press: Considerations for Eccentric and Concentric Loading." Sports 9, no. 5 (April 27, 2021): 54. http://dx.doi.org/10.3390/sports9050054.
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This study examined the effects of accentuated eccentric loading (AEL) on bench press velocities across a spectrum of concentric and eccentric loads. Ten strength trained men (bench press one-repetition maximum (1-RM): 124.3 ± 19.4 kg; relative strength ratio: 1.5 ± 0.2 kg∙body mass−1) participated. Subjects completed bench press repetitions using concentric loads from 30% to 80% 1-RM in 10% increments in each experimental session. The AEL protocols were implemented using 100% (AEL100) and 110% 1-RM (AEL110) loads during the eccentric action, while the eccentric load remained the same as the concentric for traditional loading (TRAD). Multilevel models analyzed the effects of each AEL protocol on concentric velocities across concentric loads (p < 0.05). Faster concentric velocities were observed at 30% 1-RM and 80% 1-RM with AEL100 compared to TRAD (p ≤ 0.05) but this effect was reduced for individuals moving the barbell through a greater displacement. Additionally, AEL110 presented a greater change in velocity from 30% to 80% 1-RM than TRAD (p ≤ 0.05). The AEL100 protocol resulted in faster concentric velocities throughout concentric loads of 30–80% 1-RM, but AEL110 may have been too great to elicit consistent performance enhancements. Thus, the efficacy of AEL at various concentric loads is dependent on the eccentric loading and barbell displacement.
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Smajla, Darjan, Darjan Spudić, and Nejc Šarabon. "Influence of Load and Phase of Contraction on Lateral Symmetries in Flywheel Squats." Symmetry 13, no. 1 (January 11, 2021): 111. http://dx.doi.org/10.3390/sym13010111.
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Assessment of lateral symmetries (LS) of lower limbs has been widely investigated. However, there are no studies about LS during exposure to high eccentric and concentric loads during flywheel (FW) squats. A total of 422 young, physically active participants performed squats on an FW device with different equidistant loads (0.05, 0.125 and 0.2 kg∙m2). The mean and peak force of the left and right leg were assessed for the concentric and eccentric contaction phase. LS values were calculated for each load and phase of squat. Our results showed that the absolute mean and peak force of the concentric and eccentric phase of contraction had excellent reliability, while LS values were more reliable when eccentric force was used for their calculation. Mean and peak forces were increased with the higher FW load. In general, we found a decrease in LS values in the concentric phase of contraction with the higher load. Moreover, values of LS are similar to a wide range of other functional movements. Nevertheless, symmetrical force application during squatting on a FW device should be satisfied regardless of the FW load. Due to the large sample size, our results are valuable as a reference point when athletes are evaluated during training.
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Armstrong, Richard, Vasilios Baltzopoulos, Carl Langan-Evans, Dave Clark, Jonathan Jarvis, Claire Stewart, and Thomas O’Brien. "An investigation of movement dynamics and muscle activity during traditional and accentuated-eccentric squatting." PLOS ONE 17, no. 11 (November 1, 2022): e0276096. http://dx.doi.org/10.1371/journal.pone.0276096.
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Introduction Accentuated-eccentric loading (AEL) takes advantage of the high force producing potential of eccentric muscle contractions, potentially maximising mechanical tension within the muscle. However, evidence is lacking on how AEL squatting may load the involved musculature, limiting scientifically justified programming recommendations. The purpose of this study was to investigate the effects of concentric and eccentric loads on joint loading and muscle activity of the lower limbs. Methods Resistance trained males performed traditional squatting (20–100% of concentric one-repetition maximum [1RM]) and AEL squatting with eccentric loads (110–150% of 1RM) provided by a novel motorised isotonic resistance machine (Kineo). Kinetics and kinematics of the hip, knee, and ankle joints were collected, with electromyography from the gluteus maximus, vastus lateralis, biceps femoris, and gastrocnemius medialis. A secondary cohort underwent a kinematic and electromyography analysis of squatting technique to compare Kineo and back and front barbell squatting. Results Knee joint peak eccentric moments occurred at 120% 1RM (P = 0.045), with no further increase thereafter. As eccentric load increased, the time course of moment development occurred earlier in the eccentric phase. This resulted in a 37% increase in eccentric knee extensor work from the 80% 1RM trial to the 120% 1RM trial (P<0.001). Neither hip nor ankle joints displayed further change in kinetics as eccentric load increased above 100% 1RM. Electromyographic activity during traditional squatting was ~15–30% lower in all eccentric trials than in concentric trials for all muscles. EMG plateaued between a load of 80–100% 1RM during the eccentric trials and did not increase with AEL. No significant differences in kinematics were found between Kineo and barbell squatting. Conclusions The knee extensors appear to be preferentially loaded during AEL squatting. The greater work performed during the eccentric phase of the squat as eccentric load increased suggests greater total mechanical tension could be the cause of adaptations from AEL. Our data suggest that AEL should be programmed with a load of 120% of 1RM. Further studies are needed to confirm the longer-term training effects of AEL.
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García-Ramos, Amador, Francisco Luis Pestaña-Melero, Alejandro Pérez-Castilla, Francisco Javier Rojas, and Guy Gregory Haff. "Differences in the Load–Velocity Profile Between 4 Bench-Press Variants." International Journal of Sports Physiology and Performance 13, no. 3 (March 1, 2018): 326–31. http://dx.doi.org/10.1123/ijspp.2017-0158.
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Purpose: To compare the load–velocity relationship between 4 variants of the bench-press (BP) exercise. Methods: The full load–velocity relationship of 30 men was evaluated by means of an incremental loading test starting at 17 kg and progressing to the individual 1-repetition maximum (1RM) in 4 BP variants: concentric-only BP, concentric-only BP throw (BPT), eccentric-concentric BP, and eccentric-concentric BPT. Results: A strong and fairly linear relationship between mean velocity (MV) and %1RM was observed for the 4 BP variants (r2 > .96 for pooled data and r2 > .98 for individual data). The MV associated with each %1RM was significantly higher in the eccentric-concentric technique than in the concentric-only technique. The only significant difference between the BP and BPT variants was the higher MV with the light to moderate loads (20–70%1RM) in the BPT using the concentric-only technique. MV was significantly and positively correlated between the 4 BP variants (r = .44–.76), which suggests that the subjects with higher velocities for each %1RM in 1 BP variant also tend to have higher velocities for each %1RM in the 3 other BP variants. Conclusions: These results highlight the need for obtaining specific equations for each BP variant and the existence of individual load–velocity profiles.
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Balsalobre-Fernández, Carlos, and Kristof Kipp. "Use of Machine-Learning and Load–Velocity Profiling to Estimate 1-Repetition Maximums for Two Variations of the Bench-Press Exercise." Sports 9, no. 3 (March 16, 2021): 39. http://dx.doi.org/10.3390/sports9030039.
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The purpose of the current study was to compare the ability of five different methods to estimate eccentric–concentric and concentric-only bench-press 1RM from load–velocity profile data. Smith machine bench-press tests were performed in an eccentric–concentric (n = 192) and a concentric-only manner (n = 176) while mean concentric velocity was registered using a linear position transducer. Load–velocity profiles were derived from incremental submaximal load (40–80% 1RM) tests. Five different methods were used to calculate 1RM using the slope, intercept, and velocity at 1RM (minimum velocity threshold—MVT) from the load–velocity profiles: calculation with individual MVT, calculation with group average MVT, multilinear regression without MVT, regularized regression without MVT, and an artificial neural network without MVT. Mean average errors for all methods ranged from 2.7 to 3.3 kg. Calculations with individual or group MVT resulted in significant overprediction of eccentric–concentric 1RM (individual MVT: difference = 0.76 kg, p = 0.020, d = 0.17; group MVT: difference = 0.72 kg, p = 0.023, d = 0.17). The multilinear and regularized regression both resulted in the lowest errors and highest correlations. The results demonstrated that bench-press 1RM can be accurately estimated from load–velocity data derived from submaximal loads and without MVT. In addition, results showed that multilinear regression can be used to estimate bench-press 1RM. Collectively, the findings and resulting equations should be helpful for strength and conditioning coaches as they would help estimating 1RM without MVT data.
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Park, Ju-Hyung, Seung-Jea Lee, Ho-Jin Shin, and Hwi-Young Cho. "Influence of Loads and Loading Position on the Muscle Activity of the Trunk and Lower Extremity during Squat Exercise." International Journal of Environmental Research and Public Health 19, no. 20 (October 18, 2022): 13480. http://dx.doi.org/10.3390/ijerph192013480.
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This study aimed to investigate the effect of the load and bar position on trunk and lower extremity muscle activity during squat exercise. High bar back squats (HBBS) and low bar back squats (LBBS) were performed in random order at 50%, 60%, and 70% loads of one repetition maximum by 28 experienced healthy adult men who had been performing squats for at least one year. Before the experiment, the maximal voluntary contraction of the vastus medialis, vastus lateralis, rectus femoris, biceps femoris, rectus abdominis, transverse abdominis, external oblique, and erector spinae muscles was measured by means of surface electromyography. In addition, eccentric and concentric exercises were performed for 3 s each to measure the muscle activity. There was a significant difference in muscle activity according to the load for all muscles in the eccentric and concentric phases (p < 0.05), indicating that muscle activity increased as the load increased. In addition, in the comparison between HBBS and LBBS, significant differences were shown in all lower extremity muscles and all trunk muscles except for the external oblique in the concentric phase according to the bar position (p < 0.05). HBBS showed a higher muscle activity of the lower extremity in the eccentric and concentric phases than in LBBS, while LBBS showed a higher muscle activity of the trunk muscle in the eccentric and concentric phases than in HBBS (p < 0.05). HBBS requires more force in the lower extremity than LBBS and is particularly advantageous in strengthening the muscular strength of the quadriceps. In contrast, LBBS requires more muscle activity in the trunk than HBBS and is more effective in carrying heavier loads because of the advantage of body stability. This study suggests that rehabilitation experts apply the bar position and load as important variables affecting the intensity and method of training for target muscle strengthening of the lower extremities and trunk.
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Pestaña-Melero, Francisco Luis, G. Gregory Haff, Francisco Javier Rojas, Alejandro Pérez-Castilla, and Amador García-Ramos. "Reliability of the Load–Velocity Relationship Obtained Through Linear and Polynomial Regression Models to Predict the 1-Repetition Maximum Load." Journal of Applied Biomechanics 34, no. 3 (June 1, 2018): 184–90. http://dx.doi.org/10.1123/jab.2017-0266.
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This study aimed to compare the between-session reliability of the load–velocity relationship between (1) linear versus polynomial regression models, (2) concentric-only versus eccentric–concentric bench press variants, as well as (3) the within-participants versus the between-participants variability of the velocity attained at each percentage of the 1-repetition maximum. The load–velocity relationship of 30 men (age: 21.2 [3.8] y; height: 1.78 [0.07] m, body mass: 72.3 [7.3] kg; bench press 1-repetition maximum: 78.8 [13.2] kg) were evaluated by means of linear and polynomial regression models in the concentric-only and eccentric–concentric bench press variants in a Smith machine. Two sessions were performed with each bench press variant. The main findings were: (1) first-order polynomials (coefficient of variation: 4.39%–4.70%) provided the load–velocity relationship with higher reliability than the second-order polynomials (coefficient of variation: 4.68%–5.04%); (2) the reliability of the load–velocity relationship did not differ between the concentric-only and eccentric–concentric bench press variants; and (3) the within-participants variability of the velocity attained at each percentage of the 1-repetition maximum was markedly lower than the between-participants variability. Taken together, these results highlight that, regardless of the bench press variant considered, the individual determination of the load–velocity relationship by a linear regression model could be recommended to monitor and prescribe the relative load in the Smith machine bench press exercise.
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Walker, Simon, Joanne Trezise, Guy Gregory Haff, Robert U. Newton, Keijo Häkkinen, and Anthony J. Blazevich. "Increased fascicle length but not patellar tendon stiffness after accentuated eccentric-load strength training in already-trained men." European Journal of Applied Physiology 120, no. 11 (August 9, 2020): 2371–82. http://dx.doi.org/10.1007/s00421-020-04462-x.
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Abstract Purpose This study examined whether additional external load during the eccentric phase of lower limb strength training exercises led to greater adaptations in knee extensor strength, muscle architecture, and patellar tendon properties than traditional concentric–eccentric training in already-trained men. Methods Twenty-eight men accustomed to strength training were randomized to undertake 10 weeks of supervised traditional (TRAD) or accentuated eccentric loading (AEL) or continue their habitual unsupervised (CON) strength training. TRAD and AEL trained 2∙week−1 with a six-repetition maximum (RM) session and a ten-RM session. TRAD used the same external load in both concentric and eccentric phases, while AEL used 40% greater load during the eccentric than concentric phase. Tests were performed at pre- and post-training, including: maximum unilateral isokinetic (30°·s−1) concentric, eccentric and isometric torques by isokinetic dynamometry, unilateral isometric ramp contractions with muscle–tendon ultrasound imaging to measure tendon stiffness and hysteresis, and resting vastus lateralis and medialis fascicle angle and length measured by extended-field-of-view ultrasound. Results After training, both TRAD and AEL significantly increased maximum concentric and isometric torque (p < 0.05), but only AEL increased eccentric torque (AEL: + 10 ± 9%, TRAD: + 4 ± 9%) and vastus lateralis (AEL: + 14 ± 14%, TRAD: + 1 ± 10%) and medialis (AEL: + 19 ± 8%, TRAD: + 5 ± 11%) fascicle length. Conclusion Both TRAD and AEL increased maximum knee extensor strength but only AEL increased VL and VM fascicle length. Neither training program promoted changes in fascicle angle or changes in patellar tendon properties in our already-trained men.
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Ritter, Ophélie, Laurie Isacco, Mark Rakobowchuk, Nicolas Tordi, Davy Laroche, Malika Bouhaddi, Bruno Degano, and Laurent Mourot. "Cardiorespiratory and Autonomic Nervous System Responses to Prolonged Eccentric Cycling." International Journal of Sports Medicine 40, no. 07 (May 20, 2019): 453–61. http://dx.doi.org/10.1055/a-0783-2581.
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AbstractOffering large muscle benefits despite low metabolic demand, continuous eccentric exercise appears to be an interesting alternative to concentric exercise. Nevertheless, further knowledge is needed about prolonged eccentric exercise. This work sought to investigate the cardiovascular responses to prolonged constant-load eccentric compared to concentric cycling. Ten healthy males performed two 45-min exercise sessions of either concentric or eccentric cycling separated by a month and matched for heart rate during the first 5 min of exercise. Cardiorespiratory, autonomic nervous system and vascular responses were assessed at rest, and during exercise and recovery. During cycling, oxygen uptake, cardiac output and systolic blood pressure were similar but heart rate and diastolic blood pressure were greater whereas stroke volume was lower during eccentric than concentric cycling (118±21 vs. 104±10 bpm; 77±9 vs. 65±8 mmHg; 122±12 vs. 135±13 mL). Baroreflex and noradrenaline concentration were altered during eccentric cycling, and after eccentric exercise, vascular tone was greater than after concentric cycling. We observed increased cardiovascular strain and altered baroreflex activity during eccentric compared with concentric exercise, suggesting eccentric cycling triggers greater sympathetic activity.
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Wagle, John, Christopher Taber, Kevin Carroll, Aaron Cunanan, Matt Sams, Alexander Wetmore, Garett Bingham, et al. "Repetition-to-Repetition Differences Using Cluster and Accentuated Eccentric Loading in the Back Squat." Sports 6, no. 3 (July 8, 2018): 59. http://dx.doi.org/10.3390/sports6030059.
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The current investigation was an examination of the repetition-to-repetition magnitudes and changes in kinetic and kinematic characteristics of the back squat using accentuated eccentric loading (AEL) and cluster sets. Trained male subjects (age = 26.1 ± 4.1 years, height = 183.5 ± 4.3 cm, body mass = 92.5 ± 10.5 kg, back squat to body mass ratio = 1.8 ± 0.3) completed four load condition sessions, each consisting of three sets of five repetitions of either traditionally loaded straight sets (TL), traditionally loaded cluster sets (TLC), AEL cluster sets (AEC), and AEL straight sets where only the initial repetition had eccentric overload (AEL1). Eccentric overload was applied using weight releasers, creating a total eccentric load equivalent to 105% of concentric one repetition maximum (1RM). Concentric load was 80% 1RM for all load conditions. Using straight sets (TL and AEL1) tended to decrease peak power (PP) (d = −1.90 to −0.76), concentric rate of force development (RFDCON) (d = −1.59 to −0.27), and average velocity (MV) (d = −3.91 to −1.29), with moderate decreases in MV using cluster sets (d = −0.81 to −0.62). Greater magnitude eccentric rate of force development (RFDECC) was observed using AEC at repetition three (R3) and five (R5) compared to all load conditions (d = 0.21–0.65). Large within-condition changes in RFDECC from repetition one to repetition three (∆REP1–3) were present using AEL1 (d = 1.51), demonstrating that RFDECC remained elevated for at least three repetitions despite overload only present on the initial repetition. Overall, cluster sets appear to permit higher magnitude and improved maintenance of concentric outputs throughout a set. Eccentric overload with the loading protocol used in the current study does not appear to potentiate concentric output regardless of set configuration but may cause greater RFDECC compared to traditional loading.
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Fang, Yin, Vlodek Siemionow, Vinod Sahgal, Fuqin Xiong, and Guang H. Yue. "Greater Movement-Related Cortical Potential During Human Eccentric Versus Concentric Muscle Contractions." Journal of Neurophysiology 86, no. 4 (October 1, 2001): 1764–72. http://dx.doi.org/10.1152/jn.2001.86.4.1764.
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Despite abundant evidence that different nervous system control strategies may exist for human concentric and eccentric muscle contractions, no data are available to indicate that the brain signal differs for eccentric versus concentric muscle actions. The purpose of this study was to evaluate electroencephalography (EEG)-derived movement-related cortical potential (MRCP) and to determine whether the level of MRCP-measured cortical activation differs between the two types of muscle activities. Eight healthy subjects performed 50 voluntary eccentric and 50 voluntary concentric elbow flexor contractions against a load equal to 10% body weight. Surface EEG signals from four scalp locations overlying sensorimotor-related cortical areas in the frontal and parietal lobes were measured along with kinetic and kinematic information from the muscle and joint. MRCP was derived from the EEG signals of the eccentric and concentric muscle contractions. Although the elbow flexor muscle activation (EMG) was lower during eccentric than concentric actions, the amplitude of two major MRCP components—one related to movement planning and execution and the other associated with feedback signals from the peripheral systems—was significantly greater for eccentric than for concentric actions. The MRCP onset time for the eccentric task occurred earlier than that for the concentric task. The greater cortical signal for eccentric muscle actions suggests that the brain probably plans and programs eccentric movements differently from concentric muscle tasks.
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Friden, J., P. N. Sfakianos, and A. R. Hargens. "Muscle soreness and intramuscular fluid pressure: comparison between eccentric and concentric load." Journal of Applied Physiology 61, no. 6 (December 1, 1986): 2175–79. http://dx.doi.org/10.1152/jappl.1986.61.6.2175.
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This study investigates the dynamic and resting intramuscular pressures associated with eccentric and concentric exercise of muscles in a low-compliance compartment. The left and righ leg anterior compartments of eight healthy males (ages 22–32 yr) were exercised by either concentric or eccentric contractions of the same load (400 submaximal contractions at constant rate, 20/min for 20 min at a load corresponding to 15% of individual maximal dorsiflexion torque). Tissue fluid pressures were measured with the slit-catheter technique before, during, and after the exercise. Average peak intramuscular pressure generated during eccentric exercise (236 mmHg) was significantly greater than during concentric exercise (157 mmHg, P less than 0.001). Peak isometric contraction pressure in the eccentrically exercised compartment was significantly higher both within 20 min postexercise and on the second postexercise day (P less than 0.001). Resting pressure 2 days postexercise was significantly higher on the eccentrically exercised side (10.5 mmHg) compared with the concentrically exercised (4.4 mmHg, P less than 0.05). The ability to sustain tension during postexercise isometric contractions was impaired on the “eccentric” side. Soreness was exclusively experienced in the eccentrically exercised muscles. We conclude that eccentric exercise causes significant intramuscular pressure elevation in the anterior compartment, not seen following concentric exercise, and that this may be one of the factors associated with development of delayed muscle soreness in a tight compartment.
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Sipavičienė, Saulė, Albertas Skurvydas, Irina Ramanauskienė, Žibuoklė Senikienė, and Audronė Dumčienė. "Cooling makes recovery of muscle faster after eccentric-concentric than concentric exercise." Medicina 44, no. 3 (March 17, 2008): 225. http://dx.doi.org/10.3390/medicina44030029.
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The aim of the study was to establish the influence of muscle cooling on muscle recovery after concentric and eccentric-concentric exercise. Healthy untrained males (n=40) took part in this study. During the first experiment, subjects performed concentric and during the second – eccentric-concentric exercise. During both experiments, the subjects were divided into the groups. In the first group, the muscles of the lower limbs were cooled down after the physical load, while the muscles of the subjects of the second group were not cooled. The rectal, skin, and muscle temperature was repeatedly measured immediately after physical load and after cooling of the muscle. Before exercise and after 2 min and 4, 8, 24, 48, 72 hours after performing exercise, quadriceps muscle strength, generated by electrical stimulation at frequencies of 20 Hz and 50 Hz, and maximal voluntary contraction force were registered. Serum creatine kinase levels were measured before and 24 hours after exercise. In addition, the subjects subjectively rated their muscle pain on a 10-point scale 24, 48, 72 hours after exercise. The results show that cooling applied to muscles after concentric and eccentricconcentric exercise affected the indicators of muscle damage – the activity of creatine kinase was decreased and muscle strength recovered faster. The cooling effect is greater when it is applied after eccentric-concentric exercise.
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PENG, JUI-LIN, KUAN-HUNG CHEN, SIU-LAI CHAN, and WEI-TONG CHEN. "EXPERIMENTAL AND ANALYTICAL INVESTIGATIONS OF SCAFFOLDS WITH ANCHOR ROD AND PLANK." International Journal of Structural Stability and Dynamics 09, no. 02 (June 2009): 307–32. http://dx.doi.org/10.1142/s0219455409003041.
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This paper investigates the influence of anchor rods, planks and inner knee braces on the critical load of scaffolding systems under concentric and eccentric loads in construction. The steel rebar of grade 3 is used in place of the patent anchor rod in this study. The results show that the critical load of the scaffolding system increases by 1.5 times when anchor rods of a length of 30 cm are used on two sides of each story of the scaffolding system. The critical load increases by 4 times when the scaffolding system has both the anchor rods and plank. The critical load of the scaffolding system with the anchor rods placed on each story is twice as large as that with anchor rods added every two stories; the failure mode of the system also switches from the in-plane to out-of-plane mode. The 30-cm-long anchor rod, used in place of a steel bar of grade 3, provides a good lateral restraint to the scaffolding system. Moreover, the setup plank can significantly elevate the critical load of the scaffolding system; the critical load increases approximately 1.5 times under the concentric load, and increases up to 2.2 times under the TL/4 eccentric load, defined as a load applied at a quarter distance from the end. The anchor rod and the plank should always be included in a scaffolding system to improve its stability, especially under the eccentric loads in construction.
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Chaudhry, Saira, Dylan Morrissey, Roger C. Woledge, Dan L. Bader, and Hazel R. C. Screen. "Eccentric and Concentric Exercise of the Triceps Surae: An in Vivo Study of Dynamic Muscle and Tendon Biomechanical Parameters." Journal of Applied Biomechanics 31, no. 2 (April 2015): 69–78. http://dx.doi.org/10.1123/jab.2013-0284.
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Triceps surae eccentric exercise is more effective than concentric exercise for treating Achilles tendinopathy, however the mechanisms underpinning these effects are unclear. This study compared the biomechanical characteristics of eccentric and concentric exercises to identify differences in the tendon load response. Eleven healthy volunteers performed eccentric and concentric exercises on a force plate, with ultrasonography, motion tracking, and EMG applied to measure Achilles tendon force, lower limb movement, and leg muscle activation. Tendon length was ultrasonographically tracked and quantified using a novel algorithm. The Fourier transform of the ground reaction force was also calculated to investigate for tremor, or perturbations. Tendon stiffness and extension did not vary between exercise types (P= .43). However, tendon perturbations were significantly higher during eccentric than concentric exercises (25%–40% higher,P= .02). Furthermore, perturbations during eccentric exercises were found to be negatively correlated with the tendon stiffness (R2= .59). The particular efficacy of eccentric exercise does not appear to result from variation in tendon stiffness or extension within a given session. However, varied perturbation magnitude may have a role in mediating the observed clinical effects. This property is subject-specific, with the source and clinical timecourse of such perturbations requiring further research.
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Garnacho-Castaño, Manuel V., Arturo Muñoz-González, María A. Garnacho-Castaño, and José L. Maté-Muñoz. "Power– and velocity–load relationships to improve resistance exercise performance." Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology 232, no. 4 (May 19, 2018): 349–59. http://dx.doi.org/10.1177/1754337118773587.
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Knowledge of the power– and velocity–load relationships is a key factor to guide loads during resistance training and optimize sports performance. This study compares mean velocity–, peak velocity– and power–load relationships, and determines the load which elicits maximal power output in the military press and bench press. Fifty-seven healthy, active men were randomly assigned to a bench press (n = 28) or military press (n = 29) group. In separate test sessions, concentric-only or eccentric-concentric sequences of each exercise were performed in random order as incremental isoinertial load tests. Both mean velocity and peak velocity were highly related with the load lifted (% 1RM) in both bench press and military press (mean velocity: R2 = 0.94 and 0.95; peak velocity: R2 = 0.93 and 0.93, respectively). The loads maximizing mean power and peak power output were similar for the eccentric-concentric versus concentric sequences in bench press and military press. The loads maximizing mean power and peak power were between 54% and 57.5% 1RM for the bench press and 59.8%–63.1% 1RM for the military press. For the bench press, no significant differences were observed in mean power from 30% to 80% 1RM and peak power from 30% to 95% 1RM. For the military press, no significant differences were observed in mean power from 40% to 80% 1RM and peak power from 30% to 90%/95% 1RM. The close relationship detected between mean velocity or peak velocity and load means that the % 1RM can be estimated according to mean velocity and peak velocity. In both exercises, a broad range of relative intensities could be used at which power output is not significantly different than that at maximized power output (mean = 30%/40%–80% 1RM; peak = 30%–90%/95%). Mean velocity lower than approximately 0.33 m s−1 for bench press and 0.4 m s−1 for military press, as well as peak velocity lower than approximately 0.4 m s−1 for bench press and 0.5 m s−1 for military press do not optimize power output responses. The eccentric action was a determining factor for increasing power output only in bench press.
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Hasni, Hasni, Hening Laswati Putra, and Nuniek Nugraheni. "Comparison of Acute Level of CK After Five Weeks Eccentric vs Concentric High Intensity Strength Exercise in Healthy Subject." Surabaya Physical Medicine and Rehabilitation Journal 1, no. 2 (December 24, 2019): 38. http://dx.doi.org/10.20473/spmrj.v1i2.16171.
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Background: Musculoskeletal injuries both in sport and recreational activities, at each age level, can lead to immobilization. Injury and immobilization can lead to muscle strength decrease and deconditioning. These conditions can be addressed by provision of strength training therapy especially for people with low exercise tolerance such as the elderly and patients with chronic disease. Existing studies stated eccentric exercise can increase muscle strength with less energy expenditure compared to concentric exercise. However eccentric exercise can lead to muscle damage indicated with an acute CK level increase, and eccentric exercise has not been carried out regularly for post muscle injuries and deconditioned patients. The American College of Sport Medicine (ACSM) stated strength increase and muscle hypertrophy require high intensity load strengthening exercise with a minimum load of 70% 1 Maximum Repetition. The recommended load was given to the subjects in this research. Our pleriminary study intervention was well tolerated by healthy subjects.Aim: Comparing acute CK level alteration in high intensity eccentric and concentric muscle strengthening exercise on untrained healthy subjects.Methods: Randomized pre test and post test group design. Subjects of the study (n = 16) were untrained healthy males. CK level was evaluated by laboratory test.Results: Our study showed decline of acute CK level in both groups with p value 0.65 and 0.76, respectively. No significant differences found on both groups.Conclusion: The increase of acute CK level after five weeks of eccentric strengthening exercise is not higher than that in concentric strengthening exercise.
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Hasni, Hasni, Hening Laswati Putra, and Nuniek Nugraheni. "Comparison of Acute Level of CK After Five Weeks Eccentric vs Concentric High Intensity Strength Exercise in Healthy Subject." Surabaya Physical Medicine and Rehabilitation Journal 1, no. 2 (December 24, 2019): 38. http://dx.doi.org/10.20473/spmrj.v1i2.2019.38-43.
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Background: Musculoskeletal injuries both in sport and recreational activities, at each age level, can lead to immobilization. Injury and immobilization can lead to muscle strength decrease and deconditioning. These conditions can be addressed by provision of strength training therapy especially for people with low exercise tolerance such as the elderly and patients with chronic disease. Existing studies stated eccentric exercise can increase muscle strength with less energy expenditure compared to concentric exercise. However eccentric exercise can lead to muscle damage indicated with an acute CK level increase, and eccentric exercise has not been carried out regularly for post muscle injuries and deconditioned patients. The American College of Sport Medicine (ACSM) stated strength increase and muscle hypertrophy require high intensity load strengthening exercise with a minimum load of 70% 1 Maximum Repetition. The recommended load was given to the subjects in this research. Our pleriminary study intervention was well tolerated by healthy subjects.Aim: Comparing acute CK level alteration in high intensity eccentric and concentric muscle strengthening exercise on untrained healthy subjects.Methods: Randomized pre test and post test group design. Subjects of the study (n = 16) were untrained healthy males. CK level was evaluated by laboratory test.Results: Our study showed decline of acute CK level in both groups with p value 0.65 and 0.76, respectively. No significant differences found on both groups.Conclusion: The increase of acute CK level after five weeks of eccentric strengthening exercise is not higher than that in concentric strengthening exercise.
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Moir, Gavin, Brandon Snyder, Chris Connaboy, Hugh Lamont, and Shala Davis. "Using Drop Jumps and Jump Squats to Assess Eccentric and Concentric Force-Velocity Characteristics." Sports 6, no. 4 (October 24, 2018): 125. http://dx.doi.org/10.3390/sports6040125.
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The purpose of this study was to investigate the eccentric and concentric force-velocity (Fv) characteristics recorded during drop jumps (DJ) from different heights and loaded jump squats (JS) and to determine the number of jumps required to accurately model the eccentric and concentric Fv relationships. Fourteen resistance-trained men (age: 21.9 ± 1.8 years) performed a countermovement jump (CMJ) and DJ from heights of 0.40, 0.60, and 0.80 m. JS with loads equivalent to 0%, 27%, 56%, and 85% 1-repetition maximum were performed in a separate session. Force platforms and a 3-D motion analysis system were used to record the average force ( F ¯ ) and velocity ( v ¯ ) during the absorption (CMJ, DJ40, DJ60, DJ80) and propulsion (JS0, JS27, JS56, JS85) phases of the jumps. Eccentric (absorption phase) and concentric (propulsion phase) Fv characteristics were then calculated and linear regression equations were determined when the number of jumps included was varied. F ¯ during the absorption phase significantly increased from CMJ to DJ60 while v ¯ increased significantly from CMJ to DJ80. The two-point method (CMJ, DJ80) resulted in a significantly lower y-intercept (mean difference [MD]: 0.7 N/kg) and a greater slope (MD: 0.7 Ns/m) for the eccentric Fv characteristics compared to the multiple-point method. F ¯ increased significantly and v ¯ decreased significantly with increasing external load in the JS conditions. The two-point method (JS0, JS85) resulted in a significantly greater y-intercept (MD: 1.1 N/kg) compared to the multiple-point method for the concentric Fv characteristics. Both DJ and loaded JS may provide means of assessing the eccentric and concentric Fv characteristics with only two jumps being required.
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Imran, Muhammad, Nasir Shafiq, and Ibrisam Akbar. "Effects of Eccentric Load on Un-Strengthen and CFRP Strengthened RC Beams." Advanced Materials Research 935 (May 2014): 229–32. http://dx.doi.org/10.4028/www.scientific.net/amr.935.229.
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CFRP strengthened reinforced concrete (RC) beams are usually tested under either three points or four point concentric loads; the effect of eccentricity is neglected in many studies. In this experimental program eight RC beams tested in two groups, GROUP ‘A’ & ‘B’. In group ‘A’ four RC beam tested, one control beam tested under concentric load and three under the eccentricity of 40, 60 and 80 mm respectively. The remaining four RC beams in group ’B’ strengthened using carbon fibre reinforced polymer (CFRP) strip and tested under the 60mm eccentricity. The experiment has confirmed the behaviour transformation from flexure failure to local failure due to variation in eccentricity. Therefore, the effects of eccentricity cannot be neglected and required special consideration before applying strengthening scheme on RC beam. The RC beams strengthen using CFRP have the ability to enhanced the load carrying capacity of beams tremendously, but the eccentric load effect on ductility, and failure mode of RC beams.
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Alcazar, Julian, Carlos Rodriguez-Lopez, Ignacio Ara, Ana Alfaro-Acha, Asier Mañas-Bote, Amelia Guadalupe-Grau, Francisco García-García, and Luis Alegre. "The Force-Velocity Relationship in Older People: Reliability and Validity of a Systematic Procedure." International Journal of Sports Medicine 38, no. 14 (November 10, 2017): 1097–104. http://dx.doi.org/10.1055/s-0043-119880.
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AbstractThis study compared the reliability and validity of different protocols evaluating the force-velocity (F-V) relationship and muscle power in older adults. Thirty-one older men and women (75.8±4.7 years) underwent two F-V tests by collecting the mean and peak force and velocity data exerted against increasing loads until one repetition maximum (1RM) was achieved in the leg press exercise. Two attempts per load were performed, with a third attempt when F-V points deviated from the linear F-V regression equation. Then, the subjects performed 2×3 repetitions at 60% 1RM to compare purely concentric and eccentric-concentric repetitions. The Short Physical Performance Battery was conducted to assess the validity of the different protocols. Significant differences were found in maximal power (Pmax) between mean and peak values and between protocols differing in the number of attempts per load (p<0.01). Registering mean values, a third attempt, and multiple loads (>3), was significantly more reliable (Pmax: CV=2.6%; ICC=0.99) than the other alternatives. Mean values were also observed to be more associated with physical function than peak values (R2=0.34 and 0.15, respectively; p<0.05). No significant differences were observed between concentric and eccentric-concentric repetitions. Thus, collecting mean force and velocity values against multiple loads, while monitoring the linearity of the F-V relationship, seemed to be the more adequate procedure to assess the F-V profile and muscle power in older adults.
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Perentis, Panagiotis A., Evgenia D. Cherouveim, Vassiliki J. Malliou, Nikos V. Margaritelis, Panagiotis N. Chatzinikolaou, Panayiotis Koulouvaris, Charilaos Tsolakis, Michalis G. Nikolaidis, Nickos D. Geladas, and Vassilis Paschalis. "The Effects of High-Intensity Interval Exercise on Skeletal Muscle and Cerebral Oxygenation during Cycling and Isokinetic Concentric and Eccentric Exercise." Journal of Functional Morphology and Kinesiology 6, no. 3 (July 16, 2021): 62. http://dx.doi.org/10.3390/jfmk6030062.
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The aim of the present study was to study the effects of cycling and pure concentric and pure eccentric high-intensity interval exercise (HIIE) on skeletal muscle (i.e., vastus lateralis) and cerebral oxygenation. Twelve healthy males (n = 12, age 26 ± 1 yr, body mass 78 ± 2 kg, height 176 ± 2 cm, body fat 17 ± 1% of body mass) performed, in a random order, cycling exercise and isokinetic concentric and eccentric exercise. The isokinetic exercises were performed on each randomly selected leg. The muscle and the cerebral oxygenation were assessed by measuring oxyhemoglobin, deoxyhemoglobin, total hemoglobin, and tissue saturation index. During the cycling exercise, participants performed seven sets of seven seconds maximal intensity using a load equal to 7.5% of their body mass while, during isokinetic concentric and eccentric exercise, they were performed seven sets of five maximal muscle contractions. In all conditions, a 15 s rest was adopted between sets. The cycling HIIE caused greater fatigue (i.e., greater decline in fatigue index) compared to pure concentric and pure eccentric isokinetic exercise. Muscle oxygenation was significantly reduced during HIIE in the three exercise modes, with no difference between them. Cerebral oxygenation was affected only marginally during cycling exercise, while no difference was observed between conditions. It is concluded that a greater volume of either concentric or eccentric isokinetic maximal intensity exercise is needed to cause exhaustion which, in turn, may cause greater alterations in skeletal muscle and cerebral oxygenation.
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Thumrongvut, Jaksada, and Sittichai Seangatith. "Influences of Concentric and Eccentric Loads on Buckling of Fixed-End Supported Pultruded FRP Channel Beams." Advanced Materials Research 1119 (July 2015): 721–25. http://dx.doi.org/10.4028/www.scientific.net/amr.1119.721.
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This paper presents the results of the experimental research performed on the pultruded FRP (PFRP) channel beams subjected to transversely concentric and eccentric loads. The objectives of the research work are to investigate their structural behaviors and to determine the critical buckling moments and modes of failure of the beams with various span-to-depth ratios and eccentricities. Pultruded beams are fixed-end supported at both ends for major and minor-axis flexure. The beam specimens have the cross-sectional dimension of 102×29×6 mm with span-to-depth ratios, ranging from 20 to 40. A total of 40 mono-symmetric section tests were performed. The effects of vertical load position through the cross-section were studied. Also, shear center position with concentric load and three different eccentricities were investigated ranging from 0 to-3e. The specimens were tested to final buckling. Based upon the results of this study, it is found that the load versus mid-span vertical deflection relationships of the beams are linear up to the failure. On the contrary, the load versus mid-span lateral deflection relationships are geometrically nonlinear. The general mode of failure is the flexural-torsional buckling. The eccentrically loaded specimens are failed at buckling loads lower than their concentric counterparts. Overall, the critical buckling moment decreases as the magnitude of eccentricity increases. Additionally, it is noticed thatL/dratio increases, the critical buckling moment is decreased.
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Fahmy, Mohamed F. M., and Omar A. Farghal. "Eccentricity-based design-oriented model of fiber-reinforced polymer-confined concrete for evaluation of load-carrying capacity of reinforced concrete rectangular columns." Journal of Reinforced Plastics and Composites 35, no. 23 (October 1, 2016): 1734–58. http://dx.doi.org/10.1177/0731684416667239.
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This study aimed to evaluate the load-carrying capacity of reinforced concrete rectangular columns confined with fiber-reinforced polymer composites and subjected to small eccentric loading. Seven design-oriented models of fiber-reinforced polymer-confined concrete were implemented in OpenSees software to establish the theoretical axial force-moment interaction diagram for rectangular columns. The examined models were categorized into two types: stress–strain models developed for fiber-reinforced polymer-confined non-circular concrete tested under the effect of concentric loading and others designed for fiber-reinforced polymer-confined non-circular concrete subjected to eccentric loading. The accuracy of these models was examined against the experimental results of eccentrically loaded fiber-reinforced polymer-confined reinforced concrete rectangular columns. Results indicated that the local stress–strain law obtained from the concentric compression tests would not reflect very well the local behavior of the compression zone of fiber-reinforced polymer-reinforced concrete members subjected to the combined effect of flexural and axial loadings. Adoption of a rational approach reflecting the impacts of eccentric loadings on the stress–strain relationship of the fiber-reinforced polymer-confined concrete revealed a much better evaluation of the load-carrying capacity of both reinforced concrete rectangular columns and plain concrete square columns under the effect of axial loads with various eccentricities.
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Mallinson, Joanne E., Tariq Taylor, Dumitru Constantin‐Teodosiu, Rudolf Billeter‐Clark, Despina Constantin, Martino V. Franchi, Marco V. Narici, Dorothee Auer, and Paul L. Greenhaff. "Longitudinal hypertrophic and transcriptional responses to high‐load eccentric‐concentric vs concentric training in males." Scandinavian Journal of Medicine & Science in Sports 30, no. 11 (August 26, 2020): 2101–15. http://dx.doi.org/10.1111/sms.13791.
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Gajdosik, Richard L., David W. Faris, Teri K. Kato, Pat F. Roosa, and Tamaki Matsumoto. "Accuracy and Variability of Leg Velocities during Concentric and Eccentric Actions of the Quadriceps Femoris Muscles." Perceptual and Motor Skills 84, no. 2 (April 1997): 575–86. http://dx.doi.org/10.2466/pms.1997.84.2.575.
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This study examined the ability to control leg velocities during concentric and eccentric actions of the right quadriceps muscles. Ten healthy women ( M age = 25.9 ± 3.5 yr.) were tested using the Isotonic Program of the KIN-COM II 500H dynamometer. They attempted to match velocity tracings of 10°, 20°, and 40°/sec. through 70° of knee range of motion at a load equal to 10% of their maximal mean concentric force. The actual mean velocities, mean percent deviation from the target velocities, and the coefficient of variation for both actions were calculated for 15°–75° (full range of motion), 15°—45° (shorter range of motion), and 46°–;75° (longer range of motion). Separate one-way analyses of variance with two trial factors (action x velocity) showed faster concentric velocities through the full and longer ranges of motion, and faster eccentric velocities through the shorter range of motion. Mean percent deviations indicated that the eccentric velocities were generally more accurate within all ranges of motion. Larger concentric coefficients of variation were found within the full and longer ranges of motion, and the coefficients of variation for both actions decreased as the velocities increased. An exaggerated ‘velocity overshoot’ at the onset of both actions probably contributed to differences in the velocities and coefficients of variation. The results indicated differences between the concentric and eccentric actions, explained in part by the testing methodology used and by the known mechanical and physiological characteristics of the two muscle actions.
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Ascenzi, Giampiero, Cristoforo Filetti, Valter Di Salvo, F. Javier Nuñez, Luis Suarez-Arrones, Bruno Ruscello, Fabio Massimo Francioni, and Alberto Mendez Villanueva. "Inter-limb asymmetry in youth elite soccer players: Effect of loading conditions." PLOS ONE 17, no. 6 (June 24, 2022): e0269695. http://dx.doi.org/10.1371/journal.pone.0269695.
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The presence of inter-limb asymmetries can influence strength performance and represent an injury risk factor for team sport athletes. The present study aimed to investigate the effects of changes in resistance loads using different assessment modalities on the magnitude and the direction of inter-limb asymmetry within the same leg. Fifteen young elite soccer players from the same professional academy performed rear-foot-elevated-split-squat-test at different loading conditions (body mass with no overload, 25% of body mass, 50% of body mass 50%), isokinetic knee flexor (concentric 30°·s-1, concentric 60°·s-1, eccentric 90°·s-1) and extensor (concentric 60°·s-1, eccentric 60°·s-1). The outcomes from the agreement analyses suggested moderate level agreement between body mass vs body mass 25% (Kappa = 0.46), with no agreement or fair agreement for the other between-assessment comparison. Our results demonstrated that the magnitude and direction of within-limb strength imbalances were inconsistent when compared within the same assessment under different resistance load conditions.
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El-Kashif, Khaled Farouk Omar, Abdel-Rahman Hazem, Mohamed Ahmed Rozik, and Hany Ahmed Abdalla. "Strengthening of deficient reinforced concrete columns subjected to concentric and eccentric loads." Advances in Structural Engineering 23, no. 7 (December 19, 2019): 1322–35. http://dx.doi.org/10.1177/1369433219895358.
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In this research, different techniques of repair of deficient reinforced concrete columns are compared. These include carbon fiber–reinforced polymer sheets, steel jackets, and reinforced concrete jackets. The experimental investigation includes testing of 16 deficient columns of dimensions 150 × 150 × 800 mm subjected to concentric and eccentric loading up to failure. Two main variables are considered: the load eccentricity and the strengthening technique. The experimental results showed that the three strengthening techniques used in this research significantly improved the ultimate load carrying capacity in all cases of loading. Also, in the two cases of concentric loading and big eccentricity of 150 mm, carbon fiber–reinforced polymer wrapping achieved the highest ductility and absorbed energy capacity. In addition, strengthening with reinforced concrete jacket improved the initial stiffness and toughness. The cracking load, ultimate load, and ductility of the deficient columns after strengthening were experimentally recorded and compared. The results can help the structural engineer to consider the most efficient method of repair for such columns.
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Tin, Huynh-Xuan, Ngo-Thanh Thuy, and Soo-Yeon Seo. "Structural Behavior of RC Column Confined by FRP Sheet under Uniaxial and Biaxial Load." Polymers 14, no. 1 (December 25, 2021): 75. http://dx.doi.org/10.3390/polym14010075.
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Various researches have been performed to find an effective confining method using FRP sheet in order to improve the structural capacity of reinforced concrete column. However, most of these researches were undertaken for the columns subjected to concentric compressive load or fully confined RC columns. To date, it remains hard to find studies on partially FRP-confined RC columns under eccentric load. In this manner, an experimental investigation was carried out to assess the performance of rectangular RC column with different patterns of CFRP-wrap subject to eccentric loads in this paper. The experiment consists of fourteen mid-scale rectangular RC columns of 200 mm × 200 mm × 800 mm, including five controlled columns and nine CFRP-strengthened ones. All CFRP-strengthened columns were reinforced with one layer of vertical CFRP sheet with the main fiber along the axial axis at four sides, then divided into three groups according to confinement purpose, namely unconfined, partially CFRP-confined, and fully CFRP-confined group. Two loading conditions, namely uniaxially and biaxially eccentric loads, are considered as one of the test parameters. From the test of uniaxial eccentric load, partial and full CFRP-wraps provided 19% and 33% increased load-carrying capacity at an eccentricity-to-column thickness ratio (e/h) of 0.125, respectively, compared to controlled columns, and 8% and 11% at e/h = 0.25, respectively. For the partially CFRP-confined columns subjected to biaxial eccentric load with e/h = 0.125 and 0.25, the load-carrying capacities were improved by 19% and 31%, respectively. This means that the partial confinement with CFRP effectively improves the load-carrying capacity at larger biaxial eccentric load. It was found that the load-carrying capacity could be properly predicted by using code equations of ACI 440.2R-17 and Fib Bulletin 14 Guideline for the full CFRP-confined or partially CFRP-confined columns under uniaxial load. For partially CFRP-confined columns under biaxial loading, however, the safety factors using the Fib calculation process were 20% to 31% lower than that of uniaxially loaded columns.
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Kjaer, Michael, and Katja M. Heinemeier. "Eccentric exercise: acute and chronic effects on healthy and diseased tendons." Journal of Applied Physiology 116, no. 11 (June 1, 2014): 1435–38. http://dx.doi.org/10.1152/japplphysiol.01044.2013.
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Eccentric exercise can influence tendon mechanical properties and matrix protein synthesis. mRNA for collagen and regulatory factors thereof are upregulated in animal tendons, independent of muscular contraction type, supporting the view that tendon, compared with skeletal muscle, is less sensitive to differences in type and/or amount of mechanical stimulus with regard to expression of collagen, regulatory factors for collagen, and cross-link regulators. In overused (tendinopathic) human tendon, eccentric exercise training has a beneficial effect, but the mechanism by which this is elicited is unknown, and slow concentric loading appears to have similar beneficial effects. It may be that tendinopathic regions, as long as they are subjected to a certain magnitude of load at a slow speed, independent of whether this is eccentric or concentric in nature, can reestablish their normal tendon fibril alignment and cell morphology.
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Buitrago, Sebastian, Nicolas Wirtz, Ulrich Flenker, and Heinz Kleinöder. "Physiological and metabolic responses as function of the mechanical load in resistance exercise." Applied Physiology, Nutrition, and Metabolism 39, no. 3 (March 2014): 345–50. http://dx.doi.org/10.1139/apnm-2013-0214.
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The present study aimed to investigate the relationship between the mechanical load during resistance exercise and the elicited physiological responses. Ten resistance-trained healthy male subjects performed 1 set of resistance exercise each at 55%, 70%, and 85% of 1 repetition maximum for as many repetitions as possible and in 4 training modes: 4-1-4-1 (4 s concentric, 1 s isometric, 4 s eccentric, and 1 s isometric successive actions), 2-1-2-1, 1-1-1-1, and explosive (maximum velocity concentric). Mean concentric power and total concentric work were determined. Oxygen uptake (V̇O2) was measured during exercise and for 30 min post exercise. Total volume of consumed oxygen (O2 consumed) and excess post-exercise oxygen consumption (EPOC) were calculated. Maximum blood lactate concentration (LAmax) was also determined. V̇O2 exhibited a linear dependency on mean concentric power. Mean concentric power did not have a detectable effect on EPOC and LAmax. An augmentation of total concentric work resulted in significant linear increase of O2 consumed and EPOC. Total concentric work caused a significant increase in LAmax. In general, a higher mechanical load induced a larger physiological response. An increase in mean concentric power elicited higher aerobic energy turnover rates. However, a higher extent of total concentric work augments total energy cost covered by oxidative and (or) glycolytic pathways.
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Xia, Song, and Ai Min Qin. "Nonlinear Analysis of Eccentrically Loaded Concrete Filled Circular Steel Tubular Columns." Advanced Materials Research 163-167 (December 2010): 392–97. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.392.
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Based on the appropriate numerical constitutive model of concrete filled steel tubes, layered method was applied and fiber model method based on partial sinusoidal shape for concrete filled circular steel tubular (CFST) columns under both concentric and eccentric loading was proposed. Utilizing the relationship between the curvature of the worst section and sinusoidal amplitude, a FORTRAN program was developed and the behavior of CFST columns under concentric loading, eccentric loading of equal end-moment and unequal end-moment were analyzed, showing that the analysis results are in good agreement with the experiment results from references and the fiber model method can reflect the load capacity and deformation of the columns reasonably. Thus the reliability of the present method was validated and this work is the basic for the further researches on the practical expressions of load bearing capacity for the CFST columns under both compression and bending.
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Pedersen, Helene, Atle Hole Saeterbakken, Markus Vagle, Marius Steiro Fimland, and Vidar Andersen. "Electromyographic Comparison of Flywheel Inertial Leg Curl and Nordic Hamstring Exercise Among Soccer Players." International Journal of Sports Physiology and Performance 16, no. 1 (January 1, 2021): 97–102. http://dx.doi.org/10.1123/ijspp.2019-0921.
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Purpose: The Nordic hamstring exercise (NHE) has been shown to considerably reduce hamstring injuries among soccer players. However, as the load in the NHE is the person’s own bodyweight, it is a very heavy exercise and difficult to individualize. The flywheel inertial leg curl (FLC) could be an alternative since the eccentric overload is based on the amount of work produced in the concentric movement. Therefore, the primary aim of this study was to compare the activation in the hamstrings at long muscle lengths in the NHE and the FLC in amateur soccer players. Methods: Fifteen male amateur soccer players performed 5 repetitions in each exercise in a randomized and counterbalanced order. The concentric and eccentric movements were divided into lower and upper phases. Surface EMG was measured distally, proximally, and in the middle, at both muscles. Results: In the lower phase in the eccentric movement, there were no significant differences between the 2 exercises (P = .101–.826). In the lower concentric movement, the FLC led to higher activation in all parts of both the biceps femoris (31%–52%, P < .001) and the semitendinosus (20%–35%, P = .001–.023). Conclusion: Both exercises activated the hamstrings similarly at long muscle lengths during eccentric contractions (Nordic hamstring, nonsignificantly higher). However, when performing concentric contractions, the FLC induced higher activations. Therefore, the FLC could be a useful alternative to the NHE and particularly suitable for weaker athletes before progressing to NHE.
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Lanza, Marcel B., Antônio E. M. Pertence, André G. P. Andrade, Gustavo H. Peixoto, Leonardo B. Felix, and Mauro H. Chagas. "Acute neuromuscular response during eccentric overload protocol by using a mechanical device to increase the load." Brazilian Journal of Kinanthropometry and Human Performance 19, no. 4 (November 7, 2017): 375. http://dx.doi.org/10.5007/1980-0037.2017v19n4p375.
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DOI: http://dx.doi.org/10.5007/1980-0037.2017v19n4p375 The aim of this study was to propose a mechanical device that could increase the mechanical load during the entire eccentric (ECC) action on a knee flexor machine and to compare the muscular activity when the device was used during a testing protocol. Fifteen physically active women were recruited, and they performed two protocols: control and eccentric overload. Control protocol was performed with concentric (CON) and ECC actions with similar load (60% of one repetition maximum) whilst eccentric overload protocol consisted of ECC actions with 40% more load than CON actions. Muscular activation was measured using surface electromyography of the biceps femoris (BF) and the gastrocnemius medialis (GM) muscles. ECC actions presented a higher muscular activation during eccentric overload protocol than control protocol for BF (p = 0.032), but not for the GM (p = 0.439). The mechanical device increased the mechanical load during the ECC muscle action and consequently increased the amplitude of the neural drive to the BF muscle; however, it did not increase the amplitude of the neural drive to the GM muscle.
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Subbotin, P. A., V. I. Pavlov, N. A. Polianskii, A. S. Sharykin, V. V. Deev, V. A. Badtieva, and Yu M. Ivanova. "A quick dynamics of the morphological characteristics of the myocardium in the athlete." CardioSomatics 6, no. 4 (December 15, 2015): 38–42. http://dx.doi.org/10.26442/cs45202.
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The myocardial remodeling of athletes heart is an essential process that occurs in sport exercises. However, depending on the type of load, remodeling can be of different type. An endurance load leading to eccentric cardiac remodeling, whereas power loads cause a concentric transformation of heart. Even in a same sport particular types of load can be different. This causes lead to difficulties in the differential diagnosis of physiological and pathological remodeling. Furthermore, it is believed that there must be sufficient time remodeling. We described the clinical observation, in which the athlete in the same sport, by changing the particularly of the training loads, there is objectively determined transformation of the myocardium in a relatively short period of time.
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Davis, Kermit G. "The Effect of Lifting vs. Lowering on Spinal Loading." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 40, no. 13 (October 1996): 599–603. http://dx.doi.org/10.1177/154193129604001304.
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In industry, workers perform tasks requiring both lifting and lowering. During concentric lifting, the muscles are shortening as the force is being generated. Conversely, the muscle lengthens while generating force during eccentric lowering. While research on various lifting tasks is extensive, there has been limited research performed to evaluate the lowering tasks. Most of the research that does exist on lowering has investigated muscle activity and trunk strength. None of these studies have investigated spinal loading. The current study estimated the effects of lifting and lowering on spinal loads and predicted moments imposed on the spine. Ten subjects performed both eccentric and concentric lifts under sagittally symmetric conditions. The tasks were performed under isokinetic trunk velocities of 5, 10, 20, 40, and 80 deg/s while holding a box with weights of 9.1, 18.2, and 27.3 kg. Spinal loads and predicted moments in three dimensional space were estimated by an EMG-assisted model which has been adjusted to incorporate the artifacts of eccentric lifting. Eccentric strength was found to be 56 percent greater than during concentric lifting. The lowering tasks produced significantly higher compression forces but lower anterior-posterior shear forces than the concentric lifting tasks. The differences in the spinal loads between the two lifting tasks were attributed to the internal muscle forces and unequal moments resulting from differences in the lifting path of the box. Thus, the differences between the lifting tasks resulted from different lifting styles associated with eccentric and concentric movements
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Thumrongvut, Jaksada, Natthawat Pakwan, and Samaporn Krathumklang. "Flexural-Torsional Buckling of Pultruded Fiber-Reinforced Polymer Angle Beams under Eccentric Loading." Materials Science Forum 982 (March 2020): 201–6. http://dx.doi.org/10.4028/www.scientific.net/msf.982.201.
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In this paper, the experimental study on the pultruded fiber-reinforced polymer (pultruded FRP) angle beams subjected to transversely eccentric load are presented. A summary of critical buckling load and buckling behavior for full-scale flexure tests with various span-to-width ratios (L/b) and eccentricities are investigated, and typical failure mode are identified. Three-point flexure tests of 50 pultruded FRP angle beams are performed. The E-glass fibre/polyester resin angle specimens are tested to examine the effect of span-to-width ratio of the beams on the buckling responses and critical buckling loads. The angle specimens have the cross-sectional dimension of 76x6.4 mm with span-to-width ratios, ranging from 20 to 40. Also, four different eccentricities are investigated, ranging from 0 to ±2e. Eccentric loads are applied below the horizontal flange in increments until beam buckling occurred. Based upon the results of this study, it is found that the load and mid-span vertical deflection relationships of the angle beams are linear up to the failure. In contrast, the load and mid-span lateral deflection relationships are geometrically nonlinear. The general mode of failure is the flexural-torsional buckling. The eccentrically loaded specimens are failed at critical buckling loads lower than their concentric counterparts. Also, the quantity of eccentricity increases as buckling load decreases. In addition, it is noticed that span-to-width ratio increases, the buckling load is decreased. The eccentric location proved to have considerable influence over the buckling load of the pultruded FRP angle beams.
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Wu, Lei, Yujun Qi, and Weiqing Liu. "Flexural Performance of a Hybrid Bridge Deck with Pultruded Fibre Reinforced Polymer Composite Sandwich Panels." Baltic Journal of Road and Bridge Engineering 13, no. 3 (September 28, 2018): 165–91. http://dx.doi.org/10.7250/bjrbe.2018-13.411.
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Hybrid bridge decks with the pultruded fibre reinforced polymer have advantageous properties but easily crack because of their unsatisfactory transverse strength and shear strength. This study proposed a type of bridge deck composed of innovative pultruded fibre reinforced polymer composite sandwich panels. Using four-point bending tests, concentric wheelloading tests and eccentric wheel-loading tests combined with first-order shear deformation theory, this study investigated the failure mode, flexural capacity, deformation and ductility of hybrid bridge decks under different working conditions. Under four-point bending and concentric wheel loading, the primary failure modes for this hybrid bridge deck were shear failures along the fibre direction and buckling failure of the upper panel. Under eccentric wheel loading, the primary failure mode was a torsional failure due to the eccentric load. The bearing capacities of the hybrid bridge deck under the three working conditions were 3.8, 3.5 and 3.2 times the service load of a Class I vehicle load, respectively. Besides, the hybrid bridge deck remained in the linear elastic stress state at 2.6 times the service load, indicating that this hybrid bridge deck withstands relatively large vehicle overload without visible damage. The ductility values of this hybrid bridge deck under the three working conditions were 1.79, 2.09 and 2.00, respectively, which are higher than the values for an ordinary pultruded bridge deck. Therefore, the proposed design has the relatively good energy-dissipating capacity, which improves the emergency capacity of the bridge deck.
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Wayo, Dennis Delali Kwesi, Sonny Irawan, Mohd Zulkifli Bin Mohamad Noor, Foued Badrouchi, Javed Akbar Khan, and Ugochukwu I. Duru. "A CFD Validation Effect of YP/PV from Laboratory-Formulated SBMDIF for Productive Transport Load to the Surface." Symmetry 14, no. 11 (November 2, 2022): 2300. http://dx.doi.org/10.3390/sym14112300.
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Several technical factors contribute to the flow of cuttings from the wellbore to the surface of the well, some of which are fundamentally due to the speed and inclination of the drill pipe at different positions (concentric and eccentric), the efficacy of the drilling mud considers plastic viscosity (PV) and yield point (YP), the weight of the cuttings, and the deviation of the well. Moreover, these overlaying cutting beds breed destruction in the drilling operation, some of which cause stuck pipes, reducing the rate of rotation and penetration. This current study, while it addresses the apropos of artificial intelligence (AI) with symmetry, employs a three-dimensional computational fluid dynamic (CFD) simulation model to validate an effective synthetic-based mud-drilling and to investigate the potency of the muds’ flow behaviours for transporting cuttings. Furthermore, the study examines the ratio effects of YP/PV to attain the safe transport of cuttings based on the turbulence of solid-particle suspension from the drilling fluid and the cuttings, and its velocity–pressure influence in a vertical well under a concentric and eccentric position of the drilling pipe. The resulting CFD analysis explains that the YP/PV of SBM and OBM, which generated the required capacity to suspend the cuttings to the surface, are symmetric to the experimental results and hence, the position of the drill pipe at the concentric position in vertical wells required a lower rotational speed. A computational study of the synthetic-based mud and its potency of not damaging the wellbore under an eccentric drill pipe position can be further examined.
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JENSEN, REECE C., BRYAN WARREN, CARLTON LAURSEN, and MATTHEW C. MORRISSEY. "Static pre-load effect on knee extensor isokinetic concentric and eccentric performance." Medicine & Science in Sports & Exercise 23, no. 1 (January 1991): 10???14. http://dx.doi.org/10.1249/00005768-199101000-00003.
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Abd-Alhameed, Hind Jamal, and Bushra Suhale Albusoda. "Impact of eccentricity and depth-to-breadth ratio on the behavior of skirt foundation rested on dry gypseous soil." Journal of the Mechanical Behavior of Materials 31, no. 1 (January 1, 2022): 546–53. http://dx.doi.org/10.1515/jmbm-2022-0057.
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Abstract Gypseous soils are considered one of the most problematic soils. The skirted foundation is an alternative technology that works to improve the bearing capacity and reduce settlement. This paper investigates the use of square skirted foundations resting on gypseous soil subjected to concentric and eccentric vertical load with eccentricity values of 4, 8, and 17 mm in 16 experimental model tests. To obtain the results by using this type of foundation, a small-scale physical model was designed to obtain the load–settlement behavior of the square skirted foundation; the dimension of the square footing is 100 mm × 100 mm with 1 mm thickness, the skirt depth (D s) was 0.5, 1, and 1.5B (where B is the footing width). The footing rests on dry gypseous soil with a relative density of 33%. The tests show that the gypsum content of the soil is 59%. The result shows that the highest bearing capacity for the square shape footing with D s/B = 1.5 subjected to concentric load results in an improvement ratio of 190%. For the eccentric load, with D s/B = 1.5, the increase in bearing capacity is about 120% at e = 8 mm when compared with using a foundation without a skirt.
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Chapman, A. E., G. E. Caldwell, and W. S. Selbie. "Mechanical output following muscle stretch in forearm supination against inertial loads." Journal of Applied Physiology 59, no. 1 (July 1, 1985): 78–86. http://dx.doi.org/10.1152/jappl.1985.59.1.78.
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Muscle stretch enhances force produced in both single fibers and voluntarily activated human muscle. This study determined how initial conditions of muscle stretch (and associated eccentric work), muscle length, and load inertia contributed to human concentric muscular output during maximal voluntary forearm supination. Outputs of angular velocity and concentric work over specific displacements and times of motion were calculated. Multiple regression analysis was performed using these outputs and initial conditions as dependent and independent variables, respectively. Initial conditions were shown to be significant and systematic determinants of muscle output in concentric contraction. Evidence of a temporary shift in the force-velocity curve was found and discussed regarding its beneficial contribution to load movement. Greater benefit was considered to be due to the fact that muscle stretch allows time for achievement of maximal muscular recruitment prior to concentric contraction. This produces large forces at the onset of the concentric phase, in comparison with contractions starting from rest. These findings were discussed with regard to both single- and multi-segment movement patterns.
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Papadopoulos, Christos, Konstantinos Theodosiou, Gregory C. Bogdanis, Evangelia Gkantiraga, Ioannis Gissis, Michalis Sambanis, Athanasios Souglis, and Aristomenis Sotiropoulos. "Multiarticular Isokinetic High-Load Eccentric Training Induces Large Increases in Eccentric and Concentric Strength and Jumping Performance." Journal of Strength and Conditioning Research 28, no. 9 (September 2014): 2680–88. http://dx.doi.org/10.1519/jsc.0000000000000456.
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Garnacho-Castaño, Manuel Vicente, Juan Hernández-Lougedo, Pablo García-Fernández, and José Luis Maté-Muñoz. "Effect of Muscle Action on the Kinetic and Kinematic Behavior of the Barbell during Isoinertial Strength Assessment." Applied Sciences 11, no. 5 (March 6, 2021): 2354. http://dx.doi.org/10.3390/app11052354.
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An isoinertial strength assessment was performed to examine the kinetic and kinematic behavior of the barbell during several muscle actions. Velocity–time characteristics, force–time relationship, one repetition maximum (1RM), power output, and acceleration were compared in eccentric–concentric (EC) versus concentric only (C) sequences of the bench press (BP) and military press (MP). In two separate sessions, 28 and 29 resistance-trained athletes executed EC or C sequences in random order of the BP and MP, respectively, in an incremental load test up to their 1RM. Higher values were recorded in BP-EC than in BP-C, MP-EC, or MP-C (p < 0.01) for peak acceleration, peak rate of force development, peak rate of velocity development, and power output. Significant differences were detected between exercises in terms of the portion of the concentric phase (%) at which peak acceleration was detected, or acceleration up until peak velocity was observed (p < 0.05). No differences were observed between exercises in the portion of the concentric phase where acceleration up to the braking phase took place. The eccentric muscle action prior to concentric movement was a key factor to enhance the kinematic and kinetic performance in BP exercise. No such effects of the countermovement were produced in MP.
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Mashshay, Safaa, and Adnan Al-Sibahya. "Structural Behavior of Novel ECC Short Columns Subjected to Eccentric Loading." Al-Qadisiyah Journal for Engineering Sciences 13, no. 1 (March 31, 2020): 30–35. http://dx.doi.org/10.30772/qjes.v13i1.647.
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This study was undertaken in order to investigate the structural behaviour of novel Engineering Cementitious Composites (ECC) columns subjected to eccentric loading. These columns were experimentally formulated using a hybridization of steel and polypropylene fibres. Two ratios were adopted for the steel fibres of 0.5% and 1%, whilst the polypropylene fibre was kept to be constant at a ratio of 0.5% for all of the ECC columns. The eccentric loads were applied at two eccentricities: small (h/6) and large (5h/12). A comparison was also made with the behaviour of self-compacting concrete and traditional ECC columns containing either steel or polypropylene fibres. The vertical and lateral deformations as well as the maximum load at failure were noted. The results obtained showed that the hybrid ECC columns exhibited higher load carrying capacities when compared with those of both self-compacting concrete and traditional ECC columns. The percentage increase was 30%. The hybrid ECC column samples containing 1% steel fibre did not show a signification difference in the load-deformation behaviour when it compared with that containing 0.5% steel fibre. The values of eccentricity governed the global behaviour of the tested columns. The predicated load carrying capacity of the ECC columns needs a magnification factor in case of concentric test, and to take into account the existence of fibres ratio when calculating the area of steel reinforcement for eccentric loading.
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Shaikh, Mr Shoaibaktar Yunus. "Comparative Analysis and Study the Behavior of Transmission Line Tower with using Eccentric and Concentric Bracing System with using STAAD Pro Software." International Journal for Research in Applied Science and Engineering Technology 9, no. VI (June 10, 2021): 451–58. http://dx.doi.org/10.22214/ijraset.2021.35012.
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The principle objective of this project is to “Model, Analysis and Study the behavior of transmission line tower with Concentric and Eccentric type of bracing system by using STAAD Pro software”. The Model methods used in STAAD Pro analysis are limit state Design conforming to Indian Standard Code of Practice. STAAD Pro features a state-of-the-art user interface, visualization tools, powerful analysis and design engines with advanced finite element and dynamic analysis capabilities from model generation, analysis and design to visualization and result verification, STAAD Pro is the professional’s choice. Our Final work was the “Comparative Analysis and study the behavior of transmission line tower with Concentric and Eccentric type of bracing system” under various load combinations. Using Indian equal angle section, wind zone II and seismic zone III. And considering the plane terrain
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Hortobagyi, T., and F. I. Katch. "Role of concentric force in limiting improvement in muscular strength." Journal of Applied Physiology 68, no. 2 (February 1, 1990): 650–58. http://dx.doi.org/10.1152/jappl.1990.68.2.650.
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We hypothesized that resistance training with combined eccentric and concentric actions, and concentric action only, should yield similar changes in muscular strength. Subjects in a free weight group trained three times a week for 12 wk with eccentric and concentric actions (FW, n = 16), a second group trained with concentric-only contractions using hydraulic resistance (HY; n = 12), and a control group did not train (n = 11). Training for FW and HY included five sets of supine bench press and upright squat at an intensity of 1-6 repetition maximum (RM) plus five supplementary exercises at 5-10 RM for a total of 20 sets per session for approximately 50 min. Testing at pre-, mid-, and posttraining included 1) 1 RM bench press and squat with and 2) without prestretch using free weights; 3)isokinetic peak force and power for bench press and squat at 5 degrees/s, and isotonic peak velocity and power for bench press with 20-kg load and squat with 70-kg load; 4) hydraulic peak bench press force and power, and peak knee extension torque and power at fast and slow speeds; and 5) surface anthropometry (fatfolds and girths to estimate upper arm and thigh volume and muscle area). Changes in overall fatness, muscularity, and muscle + bone cross-sectional area of the limbs did not differ between groups (P greater than 0.05). Improvements in free weight bench press and squat were similar (P greater than 0.05) in FW (approximately 24%) and HY (approximately 22%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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Murawa, Michal, Anna Fryzowicz, Jaroslaw Kabacinski, Jakub Jurga, Joanna Gorwa, Manuela Galli, and Matteo Zago. "Muscle activation varies between high-bar and low-bar back squat." PeerJ 8 (June 8, 2020): e9256. http://dx.doi.org/10.7717/peerj.9256.
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Background Differences in the muscular activity between the high-bar back squat (HBBS) and the low-bar back squat (LBBS) on the same representative group of experienced powerlifters are still scarcely investigated. The main purpose of the study was to compare the normalized bioelectrical activity and maximal angles within single homogeneous group between the HBBS and LBBS for 60% one repetition maximum (1RM), 65% 1RM and 70% 1RM. Methods Twelve healthy men (age 24.3 ± 2.8 years, height 178.8 ± 5.6 cm, body mass 88.3 ± 11.5 kg), experienced in powerlifting performed HBBS and LBBS with comparable external loads equal 60% 1RM, 65% 1RM, and 70% 1RM. Electromyography (EMG) signals of muscle groups were synchronously recorded alongside kinematic data (joints angle) by means of a motion capture system. Results EMG activity during eccentric phase of squat motion were significantly higher during LBBS than in HBBS for all selected muscles (60% 1RM and 65% 1RM) (p < 0.05). All examined muscles were more activated during concentric phase of the squat cycle (p < 0.05). In the concentric phase, significant differences between the loads were generally not observed between just 5% 1RM change in load level for LBBS. Conclusions Our results confirmed significant differences in muscles activation between both squat techniques. Muscle activity during eccentric phase of squat motion were significantly higher during LBBS than HBBS. The differences are crucial for posterior muscle chain during eccentric phase of squat cycle.
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Carlson, Luke, Brandon Jonker, Wayne L. Westcott, James Steele, and James P. Fisher. "Neither repetition duration nor number of muscle actions affect strength increases, body composition, muscle size, or fasted blood glucose in trained males and females." Applied Physiology, Nutrition, and Metabolism 44, no. 2 (February 2019): 200–207. http://dx.doi.org/10.1139/apnm-2018-0376.
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A key variable within resistance training (RT) is that of repetition duration: the time (seconds) taken to perform the concentric and eccentric muscle actions of a repetition. Research has produced equivocal results with regard to strength and muscle mass increases; many studies have created parity in the number of repetitions, but there has been disparity in the load used and the time under load (TUL). The purpose of this study was to compare load- and TUL-matched groups performing resistance exercise using different repetition durations. Fifty-nine male and female participants were randomized into 3 groups: 2s:4s (n = 18), 10s:10s (n = 20), or a group that performed 30 s of eccentric, 30 s of concentric, and 30 s of eccentric muscle actions (e.g., 1.5 repetitions; n = 21). Participants were supervised in one-on-one RT sessions 2 days/week for 10 weeks. Outcomes were 10 repetitions maximum (RM) and predicted 1RM for chest press, leg press, and pulldown exercises, as well as body composition, upper arm and thigh muscle mass, and fasted blood glucose. Analyses revealed significant increases in strength for all exercises but no between-group differences and no statistically significant time course changes for the other variables. Repetition duration does not affect the increases in strength in trained participants when exercise is performed to momentary failure. Because time constraints and perceived difficulty are often cited as barriers to exercise, it is important to recognize that the low-volume (single-set), machine-based protocol employed herein produced worthwhile strength increases in trained participants.