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&NA;. "Linebacker Stir Crazy After Surgery." Back Letter 13, no. 2 (February 1998): 24. http://dx.doi.org/10.1097/00130561-199802000-00014.
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Haun, Phil, and Colin Jackson. "Breaker of Armies: Air Power in the Easter Offensive and the Myth of Linebacker I and II in the Vietnam War." International Security 40, no. 3 (January 2016): 139–78. http://dx.doi.org/10.1162/isec_a_00226.
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Most traditional accounts identify the Linebacker I and Linebacker II campaigns as the most effective and consequential uses of U.S. air power in the Vietnam War. They argue that deep interdiction in North Vietnam played a central role in the defeat of the Easter Offensive and that subsequent strategic attacks on Hanoi forced the North Vietnamese to accept the Paris accords. These conclusions are false. The Linebacker campaigns were rather ineffective in either stopping the Communist offensive or compelling concessions. The most effective and consequential use of U.S. air power came in the form of close air support and battlefield air interdiction directly attacking the North Vietnamese Army in South Vietnam. The success of these air strikes hinged on the presence of a U.S.-operated tactical air control system that incorporated small numbers of ground advisers, air liaison officers, and forward air controllers. This system, combined with abundant U.S. aircraft and a reasonably effective allied army, was the key to breaking the Easter Offensive and compelling Hanoi to agree to the Paris accords. The effectiveness of close air support and battlefield air interdiction and the failure of deep interdiction and strategic attack in the Vietnam War have important implications for the use of air power and advisers in contemporary conflicts in Iraq, Syria, and Afghanistan.
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Drenth, Joost P. H., and Jos W. M. van der Meer. "The Inflammasome — A Linebacker of Innate Defense." New England Journal of Medicine 355, no. 7 (August 17, 2006): 730–32. http://dx.doi.org/10.1056/nejmcibr063500.
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Christina, Robert W., Jamie V. Barresi, and Paul Shaffner. "The Development of Response Selection Accuracy in a Football Linebacker Using Video Training." Sport Psychologist 4, no. 1 (March 1990): 11–17. http://dx.doi.org/10.1123/tsp.4.1.11.
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This study was undertaken to determine if response selection accuracy could be improved without sacrificing a football linebacker’s response selection speed by practicing his response selection skills in relation to various offensive plays that were seen via a videotape from a viewing angle similar to what he would see in a game. The task required the linebacker to respond to the cues of the tight end and backfield play by manipulating a joystick as accurately and quickly as possible. The data revealed that there was an improvement in response selection accuracy without sacrificing response selection speed. This finding was interpreted as evidence that training using a video-tape that displays a view of plays that is similar to what is seen in a game situation can be an effective method for improving the perceptual skills needed for response selection accuracy by a linebacker in a laboratory setting.
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Wise, Patrick Martin, and Robert A. Gallo. "Impact of Anterior Cruciate Ligament Reconstruction on NCAA FBS Football Players: Return to Play and Performance Vary by Position." Orthopaedic Journal of Sports Medicine 7, no. 4 (April 1, 2019): 232596711984105. http://dx.doi.org/10.1177/2325967119841056.
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Background: Anterior cruciate ligament (ACL) injuries are devastating for college football players. Although the change in functional performance of National Collegiate Athletic Association (NCAA) football players after reconstruction has been shown to be negligible, studies have failed to analyze the statistical performance of these players upon their return. Purpose/Hypothesis: The purpose of this study was to quantify the impact of ACL reconstruction on the statistical performance of collegiate football players. We hypothesized that statistical performance would vary by position and that running backs, wide receivers, and defensive backs, compared with preinjury and controls, would experience the largest decline in performance after returning from ACL reconstruction. Study Design: Descriptive epidemiology study. Methods: NCAA Football Bowl Subdivision (FBS) football players who experienced ACL tears between the years 2010 and 2015 were identified. The rates of return to play after surgery were determined for each position. Preinjury and postoperative performance statistics of each running back, receiver, defensive lineman, linebacker, and defensive back who met inclusion criteria were compared. A t-test analysis was used to compare the performance changes experienced by these players versus the performance changes of matched controls. Results: A total of 349 players were identified. Only 63.64% of eligible offensive linemen returned to play. Upon return, running backs experienced significant performance decreases compared with controls in carries (mean ± SD, –2.4 ± 2.7 vs 2.8 ± 1.6; P = .003), yards (–12.3 ± 15.5 vs 13.8 ± 7.8; P = .006), and receptions (–0.22 ± 0.32 vs 0.32 ± 0.23; P = .011) per game. Receivers displayed significant performance decreases compared with controls in number of touchdowns (–0.019 ± 0.110 vs 0.18 ± 0.06; P = .004), receptions (–0.11 ± 0.79 vs 1.2 ± 0.4; P = .004), and yards (–3.2 ± 10.6 vs 18.6 ± 5.4; P = .0009) per game. Linebackers demonstrated less improvement than controls in tackles for loss (0.007 ± 0.115 vs 0.31 ± 0.11; P = .0003) and sacks (0.001 ± 0.061 vs 0.10 ± 0.06; P = .026). Conclusion: Although offensive linemen were the least likely to return to play, running backs and receivers returned to play at a lower level of performance. The performance of defensive players was less affected by ACL reconstruction.
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Wagala, Nyaluma N., Philipp W. Winkler, Brian M. Godshaw, Adam Popchak, Jonathan D. Hughes, Albert Lin, and Volker Musahl. "Player Position and Labral Tear Location and Size in NCAA Division I Football Players Undergoing Arthroscopic Surgery." Orthopaedic Journal of Sports Medicine 10, no. 11 (November 1, 2022): 232596712211331. http://dx.doi.org/10.1177/23259671221133134.
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Background: Shoulder instability attributed to glenoid labral tears is common among National Collegiate Athletic Association (NCAA) football players. Certain repetitive activities by player position may contribute to instability. Purpose: To compare the location of labral tears among player positions in NCAA Division I football. Study Design: Cross-sectional study. Methods: We conducted a review of football players who underwent shoulder labral repair between 2000 and 2020 at a single institution. Inclusion criteria were NCAA Division I level, diagnosis of shoulder instability, and labral tear requiring arthroscopic repair. Exclusion criteria were prior surgery on injured shoulder and incomplete medical records. Players were divided into 3 groups: line players (offensive and defensive linemen, defensive end), skill players (defensive back, wide receiver, running back, and quarterback), and hybrid players (linebacker and tight end). Labral tear location and size were recorded using the clockface method and categorized into 6 zones: superior, anterosuperior, anteroinferior, inferior, posteroinferior, and posterosuperior. Comparison of variables was performed using chi-square test or Fisher exact test (categorical) and 1-way analysis of variance or Kruskal-Wallis H test (continuous). The Spearman rank-order correlation was used to assess relationships between continuous data. Results: Of the 53 included players, 37 (70%) were offensive linemen, defensive linemen, and linebackers. There were 29 line players, 11 skill players, and 13 hybrid players. Line players represented 55% of included players and had the most total labral tears as compared with all groups. Hybrid players had a significantly higher percentage of posterosuperior tears than line players (92% vs 52%; P = .015) and skill players (92% vs 27%; P = .002). Skill players had a significantly higher percentage of anterior tears at 3:00-4:00 and 5:00-6:00 when compared with hybrid players (82% vs 15%, P = .003; 82% vs 31%, P = .012, respectively). There was a positive correlation between labral tear size and number of suture anchors ( 0; P = .010). Conclusion: In this study of NCAA Division I football players, skill players had a higher proportion of anteroinferior labral tears, and hybrid players had a higher proportion of posterosuperior labral tears.
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Pribbenow, Merle L. "Rolling Thunder and Linebacker Campaigns: The North Vietnamese View." Journal of American-East Asian Relations 10, no. 3-4 (2001): 197–230. http://dx.doi.org/10.1163/187656101793645524.
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AbstractNorth Vietnam has the dubious distinction of having more combat experience against U.S. air power than any other nation in the world. Rolling Thunder, the first U.S. bombing campaign against North Vietnam (1965–68), lasted longer than U.S. air operations in Europe during World War II. When one adds the 1972 Linebacker air campaign against North Vietnam and the almost nine-year bombing campaign against the Ho Chi Minh Trail in Laos, only Iraq, with the air campaigns of Operations Desert Storm and Iraqi Freedom book-ending a twelve-year (1991–2003), low-intensity confrontation against U.S. aircraft over the no fly zones, faced U.S. air attacks longer. The air battles over Iraq, however, cannot be compared with the battles fought in the skies over North Vietnam. During the course of the war, more than 1,100 U.S. fixed wing aircraft were lost in combat operations.
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Leonard, Raymond W. "Learning from History: Linebacker II and U.S. Air Force Doctrine." Journal of Military History 58, no. 2 (April 1994): 267. http://dx.doi.org/10.2307/2944022.
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Drenkowski, Dana, and Lester W. Grau. "Patterns and Predictability: The Soviet Evaluation of Operation Linebacker II." Journal of Slavic Military Studies 20, no. 4 (December 7, 2007): 559–607. http://dx.doi.org/10.1080/13518040701703096.
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Sorbie, Charles. "Female Swimmers Who Looked Like Glamorous Linebackers." Orthopedics 23, no. 6 (June 2000): 534. http://dx.doi.org/10.3928/0147-7447-20000601-07.
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Gelberg, J. Nadine. "The Lethal Weapon: How the Plastic Football Helmet Transformed the Game of Football, 1939-1994." Bulletin of Science, Technology & Society 15, no. 5-6 (November 1995): 302–9. http://dx.doi.org/10.1177/0270467695015005-612.
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Under the Friday night lights of October 23, 1971, Senn High School battled Kennedy High for football victory. In the third period, to avoid a rush from the Kennedy tacklers, the Senn quarterback scrambled and threw to his halfback, Marco Cervates. Cervates caught the ball, turned and put his head down to run for extra yardage as his teammates and fans cheered. A two hundred-pound linebacker abruptly stopped Cervates' run. Cervates fell to the turf, unconscious. On November 3, 1971, at the age of seventeen, Marco Cervates died.(1)
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Pumbwe, Lilian, Christopher A. Skilbeck, and Hannah M. Wexler. "The Bacteroides fragilis cell envelope: Quarterback, linebacker, coach—or all three?" Anaerobe 12, no. 5-6 (October 2006): 211–20. http://dx.doi.org/10.1016/j.anaerobe.2006.09.004.
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Howard, William H. B. "Edge of Smile or Brink of Guffaw? Clergyman/Linebacker Contemplates Draft of 1516." JAMA: The Journal of the American Medical Association 261, no. 17 (May 5, 1989): 2504. http://dx.doi.org/10.1001/jama.1989.03420170046027.
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Pomson, Alex. "Picking Linebackers or Athletes: Reframing the Risks in Teacher Recruitment." Journal of Cases in Educational Leadership 13, no. 4 (December 2010): 11–21. http://dx.doi.org/10.1177/1555458910381463.
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Perez, Jose Raul, Jonathan Burke, Abdul Zalikha, Nicholas Schiller, Andrew NL Buskard, Dhanur Damodar, Lee D. Kaplan, and Michael G. Baraga. "Does Short Rest with Thursday Night Games Influence Injury Rates in the NFL?" Orthopaedic Journal of Sports Medicine 7, no. 7_suppl5 (July 2019): 2325967119S0034. http://dx.doi.org/10.1177/2325967119s00341.
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Objectives: The objective of this study was to evaluate the impact rest time between games may have on injury rates as it pertains to overall incidence, injury location and player position. Methods: For this descriptive epidemiological study, data was obtained from official NFL gamebooks. In-game injuries were queried for all regular season games from all 32 teams over the course of four seasons (2013 to 2016). Only injuries which resulted in a stoppage of time during gameplay were included. Player position and injured body part were taken from the following week’s injury report. Rest periods between games were classified as short (4 days), regular (6-8 days), or long (10+ days) rest. Positions were categorized into Quarterback, Skill (wide receiver, running back and defensive backs), Lineman, and Other (fullback, linebacker and tightend). Overall observed injury rates, as well as injury rates specific to anatomic location and player position, were analyzed in correlation to different rest periods. Statistical significance was determined using the ANOVAprocedure of observed mean injuries per game. Pairwise analysis, through 2 sample T-test, was conducted to assess statistical significance between short, regular and long rest. Results: A total of 2,846 injuries were identified throughout the four seasons. ANOVA testing of all 3 cohorts taken together demonstrated a statistically significant difference between injuries/game between short, regular, and long rest (p = 0.012). With short rest, a mean of 1.26 injuries/game were observed (95% CI 1.046, 1.470), which was statistically significantly different when compared to the 1.53 observed injuries/game with regular rest (95% CI 1.463, 1.601; p = 0.029). Games with short rest were not found to be significantly different when compared to the 1.34 observed injuries/game associated with long rest (95% CI 1.186, 1.486; p = 0.555). Regarding player positions, only the Other cohort achieved statistically significantly less observed injuries/game with games played on Thursday compared to regular (p=0.0002) and long (p = 0.026). The quarterback position was the only position which sustained more injuries than expected with games played on Thursday compared to both regular and long rest; however, these results did not reach statistical significance (p = 0.09). No statistical difference was found regarding injury location in correlation to differences in rest periods. Conclusion: Our data suggests that there is a significant association between the amount of rest between games and observed injuries in the NFL. Interestingly, Thursday night games were found to have fewer injuries per game when compared to games played on regular rest. Subgroup analysis revealed fewer observed injuries with short rest for linebackers, fullbacks, and tightends. Although quarterbacks were observed to have more injuries than expected on short rest, this did not reach statistical significance. The results of this study do not support that less rest associated with Thursday night games leads to higher injury rates; however, quarterback injury rates may potentially be impacted with shortened rest. [Table: see text]
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Southgate, M. Therese. "Edge of Smile or Brink of Guffaw? Clergyman/Linebacker Contemplates Draft of 1516-Reply." JAMA: The Journal of the American Medical Association 261, no. 17 (May 5, 1989): 2504. http://dx.doi.org/10.1001/jama.1989.03420170046028.
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Best, Clayton. "Experience and Career Length in Professional Football: The Effect of Positional Segregation." Sociology of Sport Journal 4, no. 4 (December 1987): 410–20. http://dx.doi.org/10.1123/ssj.4.4.410.
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This study examines positional segregation in light of recent data documenting the increased participation by black players in professional football and describes the relationships between positional segregation and experience and positional segregation and career length. The primary sample was composed of 1,508 professional football players from the 1982 season. A secondary sample of 1,371 professional football players was used to study career length. The results indicate that positional segregation is still prevalent in professional football. The recent increase in participation by black players has occurred in positions that have been primarily black in the past and at linebacker. Whites are likely to have more experience in professional football than blacks, which is explained in part by the positions in which blacks and whites are most likely to play.
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Lewes, Darby. "Literature for Linebackers: Overcoming So-called "Natural" Aversion in the Classroom." International Journal of Learning: Annual Review 13, no. 9 (2007): 195–200. http://dx.doi.org/10.18848/1447-9494/cgp/v13i09/45045.
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Ngwa, Wilfred, Rajiv Kumar, Daryl Thompson, William Lyerly, Roscoe Moore, Terry-Elinor Reid, Henry Lowe, and Ngeh Toyang. "Potential of Flavonoid-Inspired Phytomedicines against COVID-19." Molecules 25, no. 11 (June 11, 2020): 2707. http://dx.doi.org/10.3390/molecules25112707.
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Flavonoids are widely used as phytomedicines. Here, we report on flavonoid phytomedicines with potential for development into prophylactics or therapeutics against coronavirus disease 2019 (COVID-19). These flavonoid-based phytomedicines include: caflanone, Equivir, hesperetin, myricetin, and Linebacker. Our in silico studies show that these flavonoid-based molecules can bind with high affinity to the spike protein, helicase, and protease sites on the ACE2 receptor used by the severe acute respiratory syndrome coronavirus 2 to infect cells and cause COVID-19. Meanwhile, in vitro studies show potential of caflanone to inhibit virus entry factors including, ABL-2, cathepsin L, cytokines (IL-1β, IL-6, IL-8, Mip-1α, TNF-α), and PI4Kiiiβ as well as AXL-2, which facilitates mother-to-fetus transmission of coronavirus. The potential for the use of smart drug delivery technologies like nanoparticle drones loaded with these phytomedicines to overcome bioavailability limitations and improve therapeutic efficacy are discussed.
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Libkuman, Terry M., Kevin G. Love, and Paul D. Donn. "An Empirically Based Selection and Evaluation System for Collegiate Football." Journal of Sport Management 12, no. 3 (July 1998): 220–41. http://dx.doi.org/10.1123/jsm.12.3.220.
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Using a content validity approach, including job analysis, a model was developed for the selection and appraisal of college football players. Evaluation instruments were developed for offensive lineman, quarterback, running back, receiver, defensive lineman, linebacker, and defensive secondary. Criterion related validity studies were then conducted by sending the evaluation instruments to a nation-wide sample of college football coaches who evaluated players at each position. Criterion data (e.g., passing and rushing performance statistics) were collected on the evaluated players. Multiple linear regression analyses conducted by position revealed numerous significant relationships between the predictor variables and the criterion measures. The usefulness of the evaluation instruments was enhanced by developing a simple and cost effective model that generated performance predictions for each position. Strengths and weaknesses of the present system were discussed as well as the role that sport management may play in such an endeavor.
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Fahsl, Heather, and Shannon David. "A Rare Case of Lemierre’s Syndrome in a Male Division I Collegiate Football Player." International Journal of Athletic Therapy and Training 20, no. 5 (September 2015): 11–15. http://dx.doi.org/10.1123/ijatt.2014-0057.
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During the fall preseason of 2013, a 19-year-old Division I linebacker (body mass = 104 kg; height = 189 cm) attending a college football camp developed severe throat pain, quickly followed by night sweats, fever, nausea, vomiting, shortness of breath, and generalized body weakness. The athletic trainer believed that the athlete had a cold. Because symptoms did not improve, the athlete was referred to several physicians with different specialties and underwent standard testing. The ears, nose, and throat (ENT) physician recognized the signs and symptoms of Lemierre’s syndrome based on a previous case seen only once in his career. A computed tomography (CT) scan confirmed the presence of a peritonsillar abscess and thrombosis of the left internal jugular vein, which justified further investigation for this rare syndrome. A positive blood culture for Fusobacterium necrophorum confirmed the diagnosis of Lemierre’s syndrome. Several antibiotics and anticoagulation medications were prescribed and the athlete was closely monitored. After two months, he was cleared to play football.
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Shankar, Prasad R., Sarah K. Fields, Christy L. Collins, Randall W. Dick, and R. Dawn Comstock. "Epidemiology of High School and Collegiate Football Injuries in the United States, 2005-2006." American Journal of Sports Medicine 35, no. 8 (August 2007): 1295–303. http://dx.doi.org/10.1177/0363546507299745.
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Background Football, one of the most popular sports among male high school students in the United States, is a leading cause of sports-related injuries, with an injury rate almost twice that of basketball, the second most popular sport. Hypothesis Injury patterns will vary between competition and practice exposures and between levels of play (ie, high school vs. National Collegiate Athletic Association [NCAA]). Study Design Descriptive epidemiology study. Methods Football-related injury data were collected over the 2005-2006 school year from 100 nationally representative high schools via High School RIO™ (Reporting Information Online) and from 55 Division I, II, and III colleges via the NCAA Injury Surveillance System. Results Nationally, an estimated 517 726 high school football-related injuries (1881 unweighted injuries) occurred during the 2005-2006 season. The rate of injury per 1000 athlete-exposures was greater during high school competitions (12.04) than during practices (2.56). The rate of injury per 1000 athlete-exposures was also greater during collegiate competitions (40.23) than during practices (5.77). While the overall rate of injury per 1000 athlete-exposures was greater in the NCAA (8.61) than in high school (4.36), high school football players sustained a greater proportion of fractures and concussions. Running plays were the leading cause of injury, with running backs and linebackers being the positions most commonly injured. Conclusion Patterns of football injuries vary, especially by type of exposure and level of play. Future studies should continue to compare differences in injury patterns in high school and collegiate football, with particular emphasis placed on high-risk plays (running plays) and positions (running backs and linebackers).
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Cusick, Jason L., Robin J. Lund, and Travis K. Ficklin. "A Comparison of Three Different Start Techniques on Sprint Speed in Collegiate Linebackers." Journal of Strength and Conditioning Research 28, no. 9 (September 2014): 2669–72. http://dx.doi.org/10.1519/jsc.0000000000000453.
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Mason, Joshua. "Chinese Buddhist Texts: An Introductory Reader, by Graham Lock and Gary S. Linebarger." Chinese as a Second Language (漢語教學研究—美國中文教師學會學報). The journal of the Chinese Language Teachers Association, USA 54, no. 1 (September 17, 2019): 79–83. http://dx.doi.org/10.1075/csl.00007.mas.
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Mody, Kush S., Amanda N. Fletcher, Craig C. Akoh, and Selene G. Parekh. "Return to Play and Performance After Anterior Cruciate Ligament Reconstruction in National Football League Players." Orthopaedic Journal of Sports Medicine 10, no. 3 (March 1, 2022): 232596712210796. http://dx.doi.org/10.1177/23259671221079637.
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Background: Considerable variability exists in return-to-play rates after anterior cruciate ligament (ACL) injury and reconstruction (ACLR) among National Football League (NFL) players of different positions. Purpose/Hypothesis: The purpose of this study was to compare return-to-play and performance levels by position in NFL players after ACLR. It was hypothesized that (1) ACL injuries have significant effects on the careers of NFL players, including return to play and performance, and (2) players of certain positions that involve relatively less pivoting and cutting perform better after ACLR. Study Design: Descriptive epidemiology study. Methods: All NFL players who underwent ACLR between 2013 and 2018 were identified using the FantasyData injury database. Player characteristics, snap count, games played, games started, and performance metrics were collected for 3 years before and after injury using the Pro Football Reference database. Performance was measured using an approximate value (AV) algorithm to compare performance across positions and over time. Nonparametric tests were used to compare the pre- and postinjury data and the percentage change in performance between different positions. Results: Overall, 312 NFL players were included in this study, and 174 (55.8%) returned to play. Of the eligible players, only 28.5% (n = 59/207) remained in the league 3 years postinjury. Within the first 3 years postinjury, players played in fewer games (8.7 vs 13.7; P < .0001), started in fewer games (3.0 vs 8.3; P < .0001), had lower AVs (1.5 vs 4.3; P < .0001), and had decreased snap counts (259.0 vs 619.0; P < .0001) compared with preinjury. Quarterbacks were most likely to return to play (92.9% vs 53.7%; P = .0040) and to return to performance (2% vs 50% decrease in AV; P = .0165) compared with the other positions. Running backs had the largest decrease in AV (90.5%), followed by defensive linemen (76.2%) and linebackers (62.5%). Conclusion: The study findings indicated that NFL players are severely affected by ACL injury, with only 28.5% still active in the league 3 years after the injury. Running backs, defensive linemen, and linebackers performed the worst after injury. Quarterbacks were most likely to return to play and had superior postinjury performance compared with the other positions.
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Ducking, Johnny, Peter A. Groothuis, and James Richard Hill. "Compensation Discrimination: An Analysis of Linebackers, Defensive Linemen, and Defensive Backs in the National Football League." Review of Black Political Economy 44, no. 3-4 (January 2017): 251–60. http://dx.doi.org/10.1007/s12114-017-9256-y.
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Badgeley, Marcus A., Natalie M. McIlvain, Ellen E. Yard, Sarah K. Fields, and R. Dawn Comstock. "Epidemiology of 10,000 High School Football Injuries: Patterns of Injury by Position Played." Journal of Physical Activity and Health 10, no. 2 (February 2013): 160–69. http://dx.doi.org/10.1123/jpah.10.2.160.
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Background:With more than 1.1 million high school athletes playing annually during the 2005−06 to 2009−10 academic years, football is the most popular boys’ sport in the United States.Methods:Using an internet-based data collection tool, RIO, certified athletic trainers (ATs) from 100 nationally representative US high schools reported athletic exposure and football injury data during the 2005−06 to 2009−10 academic years.Results:Participating ATs reported 10,100 football injuries corresponding to an estimated 2,739,187 football-related injuries nationally. The injury rate was 4.08 per 1000 athlete-exposures (AEs) overall. Offensive lineman collectively (center, offensive guard, offensive tackle) sustained 18.3% of all injuries. Running backs (16.3%) sustained more injuries than any other position followed by linebackers (14.9%) and wide receivers (11.9%). The leading mechanism of injury was player-player contact (64.0%) followed by player-surface contact (13.4%). More specifically, injury occurred most commonly when players were being tackled (24.4%) and tackling (21.8%).Conclusions:Patterns of football injuries vary by position. Identifying such differences is important to drive development of evidence-based, targeted injury prevention efforts.
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Brooks, Jeffrey S., Kody R. Campbell, Wayne Allison, Andrew M. Johnson, and James P. Dickey. "Career Head Impact Exposure Profile of Canadian University Football Players." Journal of Applied Biomechanics 38, no. 1 (February 1, 2022): 47–57. http://dx.doi.org/10.1123/jab.2020-0228.
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This study quantified head impact exposures for Canadian university football players over their varsity career. Participants included 63 players from one team that participated in a minimum of 3 seasons between 2013 and 2018. A total of 127,192 head impacts were recorded from 258 practices and 65 games. The mean (SD) number of career impacts across all positions was 2023.1 (1296.4), with an average of 37.1 (20.3) impacts per game and 7.4 (4.4) impacts per practice. The number of head impacts that players experienced during their careers increased proportionally to the number of athletic exposures (P < .001, r = .57). Linebackers and defensive and offensive linemen experienced significantly more head impacts than defensive backs, quarterbacks, and wide receivers (P ≤ .014). Seniority did not significantly affect the number of head impacts a player experienced. Mean linear acceleration increased with years of seniority within defensive backs and offensive linemen (P ≤ .01). Rotational velocity increased with years of seniority within defensive backs, defensive and offensive linemen, running backs, and wide receivers (P < .05). These data characterize career metrics of head impact exposure for Canadian university football players and provide insights to reduce head impacts through rule modifications and contact regulations.
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Pollock, Jordan Riley, Matthew K. Doan, Walker L. Asprey, Donald L. Dulle, M. Lane Moore, Justin L. Makovicka, Jeffrey D. Hassebrock, Brittany M. Foley, and Anikar Chhabra. "Can NFL Combine Results be Used to Estimate NFL Defensive Players Longevity?" Sports Medicine International Open 5, no. 02 (August 2021): E59—E64. http://dx.doi.org/10.1055/a-1485-0031.
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AbstractThe National Football League Scouting Combine is an annual event held to evaluate football players. The results of the combine are used to identify talent and player potential. Our study aims to examine the relationship between combine drill performance (e.g., speed, power, agility, explosiveness) and career longevity. We performed a retrospective review of The National Football League combine test results for all defensive players from 2005–2015 to determine the association of each player’s combine test results with career longevity. The position that had the most significant associations for 1-year status was linebackers, with weight, 10-yard dash, 20-yard dash, 40-yard dash, broad jump, 3-cone drill, and shuttle being significantly associated with 1-year roster status. The position that had the most significant associations for 5-year status was cornerbacks, with weight, 10-yard dash, 20-yard dash, 40-yard dash, 3-cone drill, and shuttle being significantly associated with 1-year roster status. The least number of significant associations was found for safeties, with no drill being associated with 1-year roster status and only height and shuttle time significantly associated with 5-year career longevity. Our study demonstrates the utility of the combine results to help estimate the career longevity of NFL defensive players.
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Karton, Clara, Michael D. Gilchrist, and Thomas Blaine Hoshizaki. "Profiling position specific head trauma in professional American football based on impact magnitude and frequency." Neurology 91, no. 23 Supplement 1 (December 4, 2018): S1.1—S1. http://dx.doi.org/10.1212/wnl.0000000000006599.
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In American football repetitive brain trauma is associated with high risk of neurologic disorders. Head contact is integral to the game, resulting in high frequency of head contacts during a game/season. Low energy impacts that do not manifest signs recognized as injury still present metabolic and/or physiologic changes within the brain. The purpose was to estimate player position specific brain trauma profiles based on strain magnitude and impact frequency. Head impacts from 32 game films of professional football were documented and categorized based on event type, head location, and velocity for 8 positions. Inbound velocity was calculated using Kinovea 0.8.20 software. Events were reconstructed using 50th percentile Hybrid III headform, unbiased neckform, linear impactor (collisions) and monorail drop tower (falls). Maximum principal strain (MPS) within the cerebrum was calculated using UCDBTM. Frequency [p < 0.0005] and magnitude [p < 0.0005] were significantly different between the 8 positions. No significant differences in frequencies between the following; quarterback, wide receiver, and defensive back; running back, tight end, and linebacker; and between offensive and defensive linemen. Approximately 60% of documented impacts were received by linemen and tight end. The magnitudes of impacts experienced by quarterbacks were significantly different to all positions excluding wide receiver and defensive back. Wide receiver experienced significantly different magnitudes than both linemen; and differences were found between offensive linemen and defensive back. Approximately 95% of impacts experienced by linemen were below 17% MPS. Conversely, over 90% of impacts documented for quarterback were above moderate strain magnitudes (>17%). Results show risks of repetitive trauma and injury vary with position; some experience high frequency impacts of low magnitude while others receive lower hit counts of higher magnitudes. Findings showed that tight end and running back are particularly risky with relatively high brain strain magnitudes coupled with high frequency making them susceptible to high trauma loads.
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Najibi, Soheil, and John P. Albright. "The Use of Knee Braces, Part 1: Prophylactic Knee Braces in Contact Sports." American Journal of Sports Medicine 33, no. 4 (April 2005): 602–11. http://dx.doi.org/10.1177/0363546505275128.
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Surrogate knee model biomechanical studies have indicated that off-the-shelf braces provide 20% to 30% greater resistance to a lateral blow when the knee is in full extension. Custom functional braces doubled the protective effects and proved effective with the knee in some flexion. Although functional performance studies are not consistent, preventive knee braces may slow straight-ahead sprint speed, cause early fatigue, and increase muscular relaxation pressures, energy expenditure, blood lactate levels, maximal torque output, oxygen consumption, and heart rate. Two epidemiologic studies have been performed. At West Point, a randomized control study of 71 injuries in 1396 cadets indicated knee brace effectiveness with a statistically higher rate of injury in the control group (3.4/1000 exposures) than in the braced group (1.5/1000 exposures), with the most significance for medial collateral ligament sprains in defensive players. The Big Ten Conference conducted a descriptive study of 100 medial collateral ligament sprains among 987 players in different positions, strings, and types of session. Brace-wear tendency varied directly with the unbraced player counterpart's risk of medial collateral ligament sprain, with the nonplayer linemen experiencing both the greatest risk of unbraced practice session injury (0.0801 injuries/1000 exposures) and the highest incidence of brace wear (85%). During practices, there was a nonsignificant but very consistent reduction in injury rate for braced players in every position and string. During games, there was also a reduced rate for linemen and the linebacker/tight end group. The study concluded that although the issue is not closed, preventive knee braces appear to offer some protection to the medial collateral ligament from a contact injury involving a valgus blow, but there may be negative effects on performance level, leg cramping, and fatigue symptoms.
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Poor, Alexander Edward, Johannes B. Roedl, Adam C. Zoga, and William C. Meyers. "Incidence of Heterotopic Ossification Among NFL Athletes Following Platelet-Rich Plasma (PRP) for Treatment of Core Muscle Injuries (CMI)." Orthopaedic Journal of Sports Medicine 6, no. 7_suppl4 (July 1, 2018): 2325967118S0011. http://dx.doi.org/10.1177/2325967118s00114.
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Objectives: Platelet-rich plasma (PRP) therapy is an increasingly-popular treatment to promote healing in damaged tendons, ligaments, cartilage and muscles. Few studies analyze long-term effects of PRP. The authors have a busy practice treating core muscle injuries (CMI) and, in the last several years, have noticed an unusually high incidence of HO among patients with previous PRP injections for these injuries. The purpose of this study is to investigate PRP and heterotopic ossification in core muscle injuries. Methods: NFL players with core muscle injuries treated at a single institution during the 2015 season filled out questionnaires and were included in retrospective analysis. Heterotopic ossification was observed on MRI and intraoperatively and confirmed pathologically. Results: Five NFL players had previous PRP injections for core muscle injuries and 4/5 (80%)had HO. These were 2 linebackers and 2 cornerbacks. The fifth, a kicker, had no ossification but extensive fibrosis around the distal rectus abdominis and proximal adductors. These results are similar for all athletes with previous PRP injections treated around the same time period, 87% (13/15). The incidence of HO among all athletes without a previous PRP injection was 2/1088 (0.18%). Conclusion: Retrospective analysis may be overestimating the true incidence and we have yet to identify patterns related to the variations in PRP technique. But these preliminary results suggest the need for further research and a cautious approach to using PRP in the treatment of CMI.
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Stahl, Cody A., Mann J.B, Robert G. Lockie, and J. Jay Dawes. "Comparison of Estimated-1RM and 225-lb (102-kg) bench press performance between starters and non-starters among a NCAA Division I college football team." International Journal of Physical Education, Fitness and Sports 8, no. 4 (October 29, 2019): 64–75. http://dx.doi.org/10.26524/ijpefs1947.
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The estimated one-repetition maximum (1RM) bench press and NFL-225 (225-lb or 102-kg) repetition test are commonly used to assess upper-body muscular strength and endurance among football players. However, little research has been focused on the relationship of these tests to playing status. Therefore, the purpose of this study was to determine if significant relationships exist between these tests and playing status in Division I football athletes. Archival data from 31 NCAA Division I football players (age: 20.1±1.4 yrs., height: 188.07 ± 5.93 cm, body mass: 112.4 ± 19.5 kg) on the 1RM Bench press test, NFL-225 test and playing status were utilized for this analysis. A one-way ANOVA was used to detect any differences in 1RM and NFL-225 performance between skill groups: big (linemen), medium (linebackers, quarterbacks, tight ends) and small (receivers, backs, and corners) (p < 0.05). Playing status (starters vs. non-starters) were compared within position groups. A point bi-serial correlation was then utilized to examine the relationship in test performance between groups, as well as between starters and non-starters. Significant differences were discovered in NFL-225 test performance between big and small skill groups. Moderate-to-strong relationships between playing status and performance on the 1RM bench press (r = .660) and the NFL-225 test (r = .685) for the big skills group. The results of this study suggest that playing status and upper-body strength and endurance are strongly related for the big skills position group.
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Perez, Jose R., Jonathan Burke, Abdul K. Zalikha, Dhanur Damodar, Joseph S. Geller, Andrew N. L. Buskard, Lee D. Kaplan, and Michael G. Baraga. "The Effect of Thursday Night Games on In-Game Injury Rates in the National Football League." American Journal of Sports Medicine 48, no. 8 (May 15, 2020): 1999–2003. http://dx.doi.org/10.1177/0363546520919989.
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Background: Although claims of increased injury rates with Thursday night National Football League (NFL) games exist, a paucity of data exist substantiating these claims. Purpose: To evaluate the effect of rest between games on in-game injury rates as it pertains to overall injury incidence, location, and player position. Study Design: Descriptive epidemiologic study. Methods: Data were obtained from official NFL game books for regular season games from all 32 teams for the 2013-2016 seasons. All in-game injuries recorded in official game books were included. Rest periods between games were classified as short (4 days), regular (6-8 days), or long (≥10 days). Overall observed injury rates per team-game were analyzed in relation to different rest periods using negative binomial regression. For results with significant overall findings, pairwise comparisons were tested using the Wald chi-square test. Exploratory secondary analyses were performed in a similar fashion to assess differences in injury rates for the different rest periods when stratified by anatomic location and player position. Results: A total of 2846 injuries were identified throughout the 4 seasons. There was an overall significant difference in injuries per team-game between short, regular, and long rest ( P = .01). With short rest, an observed mean of 1.26 injuries per game (95% CI, 1.06-1.49) was significantly different from the 1.53 observed injuries per game with regular rest (95% CI, 1.46-1.60; P = .03), but not compared with the 1.34 observed injuries per game with long rest ( P = .56). For player position, only the tight end, linebacker, and fullback group demonstrated significant differences between the injury rates for different rest categories. Quarterback was the only position with more injuries during games played on Thursday compared with both regular and long rest. This specific analysis was underpowered and the difference was not significant ( P = .08). No differences were found regarding injury rates in correlation with differences in rest periods with different injury locations. Conclusion: A short rest period between games is not associated with increased rates of observed injuries reported in NFL game books; rather, our data suggest there are significantly fewer injuries for Thursday night games compared with games played on regular rest. Future research correlating rest and quarterback injury rates is warranted.
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Lessley, David J., Richard W. Kent, James R. Funk, Christopher P. Sherwood, Joseph M. Cormier, Jeff R. Crandall, Kristy B. Arbogast, and Barry S. Myers. "Video Analysis of Reported Concussion Events in the National Football League During the 2015-2016 and 2016-2017 Seasons." American Journal of Sports Medicine 46, no. 14 (November 6, 2018): 3502–10. http://dx.doi.org/10.1177/0363546518804498.
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Background: Concussions in American football remain a high priority of sports injury prevention programs. Detailed video review provides important information on causation, the outcomes of rule changes, and guidance on future injury prevention strategies. Purpose: Documentation of concussions sustained in National Football League games played during the 2015-2016 and 2016-2017 seasons, including consideration of video views unavailable to the public. Study Design: Descriptive epidemiology study. Methods: All reported concussions were reviewed with all available video footage. Standardized terminology and associated definitions were developed to describe and categorize the details of each concussion. Results: Cornerbacks sustained the most concussions, followed by wide receivers, then linebackers and offensive linemen. Half (50%) of concussions occurred during a passing play, 28% during a rushing play, and 21% on a punt or kickoff. Tackling was found to be the most common activity of concussed players, with the side of the helmet the most common helmet impact location. The distribution of helmet impact source—the object that contacted the concussed player’s helmet—differed from studies of earlier seasons, with a higher proportion of helmet-to-body impacts (particularly shoulder) and helmet-to-ground impacts and with a lower proportion of helmet-to-helmet impacts. Helmet-to-ground concussive impacts were notable for the high prevalence of impacts to the back of the helmet and their frequency during passing plays. Conclusion: Concussion causation scenarios in the National Football League have changed over time. Clinical Relevance: The results of this study suggest the need for expanded evaluation of concussion countermeasures beyond solely helmet-to-helmet test systems, including consideration of impacts with the ground and with the body of the opposing player. It also suggests the possibility of position-specific countermeasures as part of an ongoing effort to improve safety.
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Kaplan, Lee D., David C. Flanigan, John Norwig, Patrick Jost, and James Bradley. "Prevalence and Variance of Shoulder Injuries in Elite Collegiate Football Players." American Journal of Sports Medicine 33, no. 8 (August 2005): 1142–46. http://dx.doi.org/10.1177/0363546505274718.
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Background Shoulder injuries are the fourth most common musculoskeletal injury encountered in American football players. There is little information in the literature on the role of playing position in the type of shoulder injuries seen. Hypothesis There is a high prevalence of shoulder injuries in elite collegiate American football players, with type of injury varying by playing position. Study Design Cohort study (prevalence); Level of evidence, 3. Methods A total of 336 elite collegiate American football players were invited to the National Football League Combine for physical testing and medical evaluation. Current and historical data were evaluated for the purpose of this study, and all players underwent radiographic examinations, including plain radiographs and/or magnetic resonance imaging when necessary. All shoulder pathological conditions and shoulder surgical procedures were recorded. Players were categorized by position for the analysis of position-specific trends. Results Of the players, 50% had a history of shoulder injuries, with a total of 226 shoulder injuries (1.3 injuries per player injured); 56 players (34%) had a total of 73 surgeries. The most common injuries were acromioclavicular separation (41%), anterior instability (20%), rotator cuff injury (12%), clavicle fracture (4%), and posterior instability (4%). The most common surgeries performed were anterior instability reconstruction (48%), Mumford/Weaver-Dunn surgery (15%), posterior instability surgery (10%), and rotator cuff surgery (10%). Shoulder injuries were more common in quarterbacks and defensive backs. Surgery was more common in linebackers or linemen. A history of anterior instability was more common in defensive players, with surgery required 76% of the time. Linemen had more rotator cuff injuries and posterior instability than players in other positions. Conclusion Shoulder injuries are common injuries in elite collegiate football players, with one-third undergoing surgical procedures. There are definitive trends in the types of injuries per player position.
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Siibak, Andra. "Book review: Rachel Barr and Deborah Nichols Linebarger (Eds.), Media exposure during infancy and early childhood: The effects of content and context on learning and development." Mobile Media & Communication 8, no. 1 (December 20, 2019): 144–46. http://dx.doi.org/10.1177/2050157919883065b.
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Gellner, Ryan A., Eamon T. Campolettano, Eric P. Smith, and Steven Rowson. "Are specific players more likely to be involved in high-magnitude head impacts in youth football?" Journal of Neurosurgery: Pediatrics 24, no. 1 (July 2019): 47–53. http://dx.doi.org/10.3171/2019.2.peds18176.
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OBJECTIVEYouth football attracts approximately 3.5 million participants every year, but concern has recently arisen about the long-term effects of experiencing repetitive head accelerations from a young age due to participation in football. The objective of this study was to quantify total involvement in high-magnitude impacts among individual players in youth football practices. The authors explored the relationship between the total number of high-magnitude accelerations in which players were involved (experienced either by themselves or by other players) during practices and the number of high-magnitude accelerations players experienced.METHODSA local cohort of 94 youth football players (mean age 11.9 ± 1.5, mean body mass 50.3 ± 16.4 kg) from 4 different teams were recruited and outfitted with helmet-mounted accelerometer arrays. The teams were followed for one season each for a total of 128 sessions (practices, games, and scrimmages). All players involved in high-magnitude (greater than 40g) head accelerations were subsequently identified through analysis of practice film.RESULTSPlayers who experienced more high-magnitude accelerations were more likely to be involved in impacts associated with high-magnitude accelerations in other players. A small subset of 6 players (6%) were collectively involved in 230 (53%) high-magnitude impacts during practice, were involved in but did not experience a high-magnitude acceleration 78 times (21% of the 370 one-sided high-magnitude impacts), and experienced 152 (30%) of the 502 high-magnitude accelerations measured. Quarterbacks/running backs/linebackers were involved in the greatest number of high-magnitude impacts in practice and experienced the greatest number of high-magnitude accelerations. Which team a player was on was an important factor, as one team showed much greater head impact exposure than all others.CONCLUSIONSThis study showed that targeting the most impact-prone players for individualized interventions could reduce high-magnitude acceleration exposure for entire teams. These data will help to further quantify elevated head acceleration exposure and enable data-driven interventions that modify exposure for individual players and entire teams.
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Wise, Patrick M., Anna M. Ptasinski, and Robert A. Gallo. "Pectoralis Major Ruptures in the National Football League: Incidence, RTP, and Performance Analysis." Orthopaedic Journal of Sports Medicine 9, no. 6 (June 1, 2021): 232596712110187. http://dx.doi.org/10.1177/23259671211018707.
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Background: While pectoralis major (PM) tears are rare injuries in National Football League (NFL) athletes (previous study reported only 10 PM ruptures between 2000 and 2010), the incidence of these injuries has increased over the past decade. The impact these injuries have on a player’s performance after return has not been measured. Purpose/Hypothesis: To identify player characteristics that may predispose to PM tears and to determine the impact of this injury on return to play and performance. We hypothesized that there would be no difference in performance between the year before and after their injury. Study Design: Descriptive epidemiology study. Methods: NFL players who experienced PM tears between the years 2010 and 2018 were identified using publicly available reports. Several individual player characteristics were identified and recorded, and the return-to-play rates after injury were determined for each position. The pre- and postinjury Pro Football Focus grades of players who met inclusion criteria were compared. A paired t test analysis of the change in player performance was used for analysis. Results: In this study, 63 ruptures were identified between 2010 and 2018. Linebackers had the highest incidence of PM tear compared with any other position. Of all injuries, 79.3% were sustained by defensive players. The majority of PM tears occurred during games. Only 6.9% of players who sustained the injury were suspended for performance-enhancing drug use during their professional career. A total of 85.7% of players returned to play in the NFL after injury. Among those who returned to play there were no significant changes in player performance from pre- to post-injury. Conclusion: NFL players demonstrated 85.7% return-to-play rates and no significant drop-off in performance after PM ruptures. During the time period studied, there was an increase in incidence of PM ruptures compared with the previous decade. Further investigation is needed to determine potential causes for the increased incidence of PM ruptures in NFL players.
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Crisco, Joseph J., Russell Fiore, Jonathan G. Beckwith, Jeffrey J. Chu, Per Gunnar Brolinson, Stefan Duma, Thomas W. McAllister, Ann-Christine Duhaime, and Richard M. Greenwald. "Frequency and Location of Head Impact Exposures in Individual Collegiate Football Players." Journal of Athletic Training 45, no. 6 (November 1, 2010): 549–59. http://dx.doi.org/10.4085/1062-6050-45.6.549.
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Abstract Context: Measuring head impact exposure is a critical step toward understanding the mechanism and prevention of sport-related mild traumatic brain (concussion) injury, as well as the possible effects of repeated subconcussive impacts. Objective: To quantify the frequency and location of head impacts that individual players received in 1 season among 3 collegiate teams, between practice and game sessions, and among player positions. Design: Cohort study. Setting: Collegiate football field. Patients or Other Participants: One hundred eighty-eight players from 3 National Collegiate Athletic Association football teams. Intervention(s): Participants wore football helmets instrumented with an accelerometer-based system during the 2007 fall season. Main Outcome Measure(s): The number of head impacts greater than 10g and location of the impacts on the player's helmet were recorded and analyzed for trends and interactions among teams (A, B, or C), session types, and player positions using Kaplan-Meier survival curves. Results: The total number of impacts players received was nonnormally distributed and varied by team, session type, and player position. The maximum number of head impacts for a single player on each team was 1022 (team A), 1412 (team B), and 1444 (team C). The median number of head impacts on each team was 4.8 (team A), 7.5 (team B), and 6.6 (team C) impacts per practice and 12.1 (team A), 14.6 (team B), and 16.3 (team C) impacts per game. Linemen and linebackers had the largest number of impacts per practice and per game. Offensive linemen had a higher percentage of impacts to the front than to the back of the helmet, whereas quarterbacks had a higher percentage to the back than to the front of the helmet. Conclusions: The frequency of head impacts and the location on the helmet where the impacts occur are functions of player position and session type. These data provide a basis for quantifying specific head impact exposure for studies related to understanding the biomechanics and clinical aspects of concussion injury, as well as the possible effects of repeated subconcussive impacts in football.
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Broglio, Steven P., Richelle M. Williams, Kathryn L. O'Connor, and Jason Goldstick. "Football Players' Head-Impact Exposure After Limiting of Full-Contact Practices." Journal of Athletic Training 51, no. 7 (July 1, 2016): 511–18. http://dx.doi.org/10.4085/1062-6050-51.7.04.
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Context: Sporting organizations limit full-contact football practices to reduce concussion risk and based on speculation that repeated head impacts may result in long-term neurodegeneration. Objective: To directly compare head-impact exposure in high school football players before and after a statewide restriction on full-contact practices. Design: Cross-sectional study. Setting: High school football field. Patients or Other Participants: Participants were varsity football athletes from a single high school. Before the rule change, 26 athletes (age = 16.2 ± 0.8 years, height = 179.6 ± 6.4 cm, weight = 81.9 ± 13.1 kg) participated. After the rule change, 24 athletes (age = 15.9 ± 0.8 years, height = 178.3 ± 6.5 cm, weight = 76.2 ± 11.6 kg) participated. Nine athletes participated in both years of the investigation. Main Outcome Measure(s): Head-impact exposure was monitored using the Head Impact Telemetry System while the athletes participated in football games and practices in the seasons before and after the rule change. Head-impact frequency, location, and magnitude (ie, linear acceleration, rotational acceleration, and Head Impact Telemetry severity profile [HITsp], respectively) were measured. Results: A total of 15 398 impacts (592 impacts per player per season) were captured before the rule change and 8269 impacts (345 impacts per player per season) after the change. An average 42% decline in impact exposure occurred across all players, with practice-exposure declines occurring among linemen (46% decline); receivers, cornerbacks, and safeties (41% decline); and tight ends, running backs (including fullbacks), and linebackers (39% decline). Impact magnitudes remained largely unchanged between the years. Conclusions: A rule change limiting full-contact high school football practices appears to have been effective in reducing head-impact exposure across all players, with the largest reduction occurring among linemen. This finding is likely associated with the rule modification, particularly because the coaching staff and offensive scheme remained consistent, yet how this reduction influences concussion risk and long-term cognitive health remains unknown.
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Godek, Sandra Fowkes, Chris Peduzzi, Richard Burkholder, Steve Condon, Gary Dorshimer, and Arthur R. Bartolozzi. "Sweat Rates, Sweat Sodium Concentrations, and Sodium Losses in 3 Groups of Professional Football Players." Journal of Athletic Training 45, no. 4 (July 1, 2010): 364–71. http://dx.doi.org/10.4085/1062-6050-45.4.364.
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Abstract Context: Sweat sodium losses have never been reported in a large cohort of American football players. Objective: To compare sweat rates (SwtRs), sweat sodium concentrations (SwtNa+), and sodium losses in 3 groups of players (backs and receivers [BK], linebackers and quarterbacks [LB/QB], and linemen [LM]) to determine if positional differences and, therefore, size differences exist. Design: Observational study. Setting: Data were collected during practices in the second week of 2 consecutive training camps. The wet bulb globe temperature was 78.5°F ± 3.5°F (25.9°C ± 1.9°C). Patients or Other Participants: Eighteen BK, 12 LB/QB, and 14 LM volunteered. Intervention(s): Sterile sweat patches were applied to the right forearm after the skin was appropriately cleaned. The patches were removed during practice, placed in sterile tubes, centrifuged, frozen, and later analyzed by flame photometry. Main Outcome Measure(s): Sweat rate, SwtNa+, and sodium loss. We calculated SwtR by change in mass adjusted for urine produced and fluids consumed divided by practice time in hours. Results: Other than age, physical characteristics were different among groups (P < .001). The SwtR was different among groups (F2,41 = 7.3, P = .002). It was lower in BK (1.42 ± 0.45 L/h) than in LB/QB (1.98 ± 0.49 L/h) (P < .05) and LM (2.16 ± 0.75 L/h) (P < .01), but we found no differences between SwtRs for LB/QB and LM. The SwtNa+ was not different among groups (BK = 50 ± 16 mEq/L, LB/QB = 48.2 ± 23 mEq/L, and LM = 52.8 ± 25 mEq/L) and ranged from 15 to 99 mEq/L. Sweat sodium losses ranged from 642 mg/h to 6.7 g/h, and findings for group comparisons approached significance (P = .06). On days when players practiced 4.5 hours, calculated sodium losses ranged from 2.3 to 30 g/d. Conclusions: The BK sweated at lower rates than did the midsized LB/QB and large LM, but LB/QB sweated similarly to LM. Sweat sodium concentration and daily sodium losses ranged considerably. Heavy, salty sweaters require increased dietary consumption of sodium during preseason.
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Chyhrin, Oleh, Kateryna Barandych, and Maksym Gladskyi. "AUGMENTED REALITY APPLICATION FOR ASSEMBLY DESIGN OF CYCLOIDAL GEARBOX." Bulletin of Kyiv Polytechnic Institute. Series Instrument Making, no. 64(2) (December 24, 2022): 71–76. http://dx.doi.org/10.20535/1970.64(2).2022.270030.
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Modern productions are moving towards full automation of product manufacturing, however, for now some physical
processes cannot be fully automated, and that is why it remains some manual performance using labor resources. Similar processes occur both in mass production and in individual or experimental production.
In the startup project LineBar, it was proposed to use a cycloidal gearbox to increase the torque of the stepper motor, however, due to the complexity of the design, it was required to develop the tolling to reduce the time for assembly operation settlement. Augmented reality technologies were used to implement such a task.
This paper presents the tooling development process. It is described a preparation of 3D model of cycloidal gearbox for Unity application, which has all the necessary functions to create the tooling. The process of basic functionality development is shown, which is a display of 3D model on prepared marker, assembly and disassembly animation of cycloidal gearbox. To expand the functionality, the ability to step-by-step switch the animation of gear assembly has been added. Animations are controlled using the created "Animation", "Forward" and "Back" buttons.
The process of the annotation development function of 3D models is described, namely the creation of 3D annotation objects, the development of the information display function considering a placement of component unit at the center of the screen, and the implementation of the annotation reversal function when the user's camera is rotated.
The result of this work is created application, which can be used to reduce the time for the assembly operation of the cycloidal gearbox. It was found a 30% time reduction for assembly operation using the application compared to the regular method.
For future work, it is proposed to automate the preparation of 3D models, their animation and annotation in the Unity environment, to reduce the time for expanding the application functions, which will affect the scaling the application to larger production.
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Stapleton, Erik, Randy Cohn, and Colin Burgess. "The Impact of the Helmet-Lowering Rule on Regular Season NFL Injuries." Orthopaedic Journal of Sports Medicine 8, no. 7_suppl6 (July 1, 2020): 2325967120S0040. http://dx.doi.org/10.1177/2325967120s00403.
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Objectives: The National Football League (NFL) has been under growing scrutiny from the public due to the apparent rise in concussions and head injuries and the subsequent deleterious effects. In efforts to address these concerns, the NFL implemented a new “Helmet-lowering” rule prior to the 2018-2019 season. This rule is defined as “a foul if a player lowers his head to initiate and make contact with his helmet against an opponent.” The purpose of this paper was to compare incidence of injuries in NFL players prior to and after implementation of this new rule. Methods: NFL injury data was retrospectively reviewed from public league records for all players in regular season games played from the 2017 and 2018 NFL seasons. An injury was defined as any player listed on a team’s injury report that was not previously documented on the team’s report one week preceding the index injury. Injury rates were reported as the number of injuries per 1000 athletic exposures (AE’s). Athletic exposures were defined as equal to the sum of the total number of NFL regular-season games played. Relative risk (with 95% CI) was calculated by using the number of injuries per 1000 athletic exposures for the season before and after the new rule implementation. Risk reduction was then calculated for the overall injuries, upper/lower extremity and head injuries. Results: Over the 2 seasons there were a total of 2,774 injuries identified. After rule implementation at the beginning of the 2018 season, there was an overall relative risk (RR) of 0.91 for injury (95% CI 0.88 to 0.95, p<0.0001), with an injury risk reduction of 8.73%. Upper extremity injuries had a RR of 0.76 (95% CI 0.65 to 0.87, p=0.0005) and a risk reduction of 24.10%. Lower extremity injuries had a RR of 0.91 (95% CI 0.87 to 0.96, p=0.0005) with a risk reduction of 8.63%. In concussions and head injuries there was an overall RR of 0.55 for injury (95% CI 0.44 to 0.69, p<0.0001), with an injury risk reduction of 45.10%. Wide receivers and linebackers were most commonly injured players on offense and defense, respectively. Conclusion: Implementation of the new Helmet-Lowering rule seems to have played a role in significantly decreasing the NFL athlete’s risk of injury across all measures, most notably in concussion and head injuries.
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Simpson, Roger L., M. Ghodbane, and B. E. Mcgrath. "Surface pressure fluctuations in a separating turbulent boundary layer." Journal of Fluid Mechanics 177 (April 1987): 167–86. http://dx.doi.org/10.1017/s0022112087000909.
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Measurements of surface pressure-fluctuation spectra and wave speeds are reported for a well-documented separating turbulent boundary layer. Two sensitive instrumentation microphones were used in a new technique to measure pressure fluctuations through pinhole apertures in the flow surface. Because a portion of the acoustic pressure fluctuations is the same across the nominally two-dimensional turbulent flow, it is possible to decompose the two microphone signals and obtain the turbulent flow contributions to the surface pressure spectra. In addition, data from several earlier attached-flow surface-pressure-fluctuation studies are re-examined and compared with the present measurements.The r.m.s. of the surface pressure fluctuation p′ increases monotonically through the adverse-pressure-gradient attached-flow region and the detached-flow zone. Apparently p′ is proportional to the ratio α of streamwise lengthscale to lengthscales in other directions. For non-equilibrium separating turbulent boundary layers, α is as much as 2.5, causing p′ to be higher than equilibrium layers with lower values of α.The maximum turbulent shearing stress τM appears to be the proper stress on which to scale p′; p′/τM from available data shows much less variation than when p′ is scaled on the wall shear stress. In the present measurements p′/τM increases to the detachment location and decreases downstream. This decrease is apparently due to the rapid movement of the pressure-fluctuation-producing motions away from the wall after the beginning of intermittent backflow. A correlation of the detached-flow data is given that is derived from velocity- and lengthscales of the separated flow.Spectra Φ (ω) for ωδ*/U∞ > 0.001 are presented and correlate well when normalized on the maximum shearing stress τM. At lower frequencies, for the attached flow Φ (ω) ∼ ω−0.7 while Φ(ω) ∼ (ω)−3 at higher frequencies in the strong adverse-pressuregradient region. After the beginning of intermittent backflow, Φ(ω) varies with ω at low frequencies and ω−3 at high frequencies; farther downstream the lower-frequency range varies with ω1.4.The celerity of the surface pressure fluctuations for the attached flow increases with frequency to a maximum; at higher frequencies it decreases and agrees with the semi-logarithmic overlap equation of Panton & Linebarger. After the beginning of the separation process, the wave speed decreases because of the oscillation of the instantaneous wave speed direction. The streamwise coherence decreases drastically after the beginning of flow reversal.
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Brown, Isaiah, Scott Anderson, Anwar Ahmed, Barry Boden, and Jeremy Huckleby. "Poster 116: Traumatic Brain Injury in High School and College American Football Athletes, 2002-2019: Increasing Risk of Injury and Fatality." Orthopaedic Journal of Sports Medicine 10, no. 7_suppl5 (July 1, 2022): 2325967121S0067. http://dx.doi.org/10.1177/2325967121s00677.
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Objectives: A prior report revealed an average of 7.2 (0.67 per 100,000 participants) traumatic brain injuries (TBI) per year in high school (HS) and college football players from 1989 through 2002. Our goal is to update the profile of TBI in HS and college football players and evaluate the efficacy of state laws implemented to reduce brain injuries. Methods: We retrospectively reviewed 17 academic years (July 2002 through June 2019) of TBIs catalogued by the National Registry of Catastrophic Sports Injuries (NRCSI). Descriptive statistics were collected using Excel and SPSS. The incidence of TBI was compared with the prior 13-year period. In addition, the incidence of TBI was assessed at the HS level during the pre (2002-2009[BB3] [BI([4] [BI([5] ), transitional (2009-2014), and post (2014-2019) universal adoption time periods of the Lystedt laws. Multinomial logistic regression analyses were performed to determine the odds of TBI based on level of play, Lystedt law adoption eras, and position played. Results: During the study period, there was a total of 177 TBIs (10.4 per year, 0.82 per 100,000 participants): 164 (92.7%, 0.81 per 100,000, 9.65 per year) in HS athletes and 13 (6.6%, 0.96 per 100,000, 0.76 per year) in college athletes. The risk of TBI at the HS level was significantly higher than at the college level (1.99: 95% CI, 1.137-3.517, P<0.0001). Compared to the prior 13-year period, the risk of TBI during the study period was 1.29 (95% CI, 1.004-1.656, P=0.047) with a greater increase at the college (4.40: 95% CI, 0.993-19.5, P=0.051) than the HS level (1.22: 95% CI, 0.946-1.577, P=0.124). There were 51 fatalities (3 per year, 0.24 per 100,000 participants) with a risk of 1.63 (95% CI: 0.65-4.11, P = 0.3) at the college (n=5, 0.29 per year, 0.36/100,000) compared with the HS (n=46, 2.71 per year, 0.22 per 100,000) levels. The risk of a fatality in the current study compared with the prior study was 4.32 (95% CI: 2.05-9.09, P= 0.0001) with higher risks at both the HS (5.17, 95% CI: 2.21-12.1, P =0.0002) and college (1.8, 95% CI: 0.35-9.3, P = 0.48) levels. The incidence of TBI in HS increased significantly from the pre (0.57 per 100,000) to the transitional (0.78 per 100,000, OR = 4.7, P<0.001), and from the transitional to the post universal adoption (1.17 per 100,000, OR = 13.7, P<0.0001) eras of the Lystedt law. The most common positions among HS and college athletes suffering TBI were linebacker (26, 22.6%) and running back (20, 17.4%), and defensive back (16, 13.9%). Conclusions: The incidence of TBI has increased 29% during the 2002-2019 period compared to the prior 13-year period with a 440% and 22% rise in college and HS cases, respectively. The risk of fatality increased 432% compared to the prior 13-year period with an increase of 517% and 180% at the HS and college levels, respectively. The increased incidence of TBI at the HS level has occurred despite implementation of the Lystedt laws. Further research is necessary to determine the risk factors for TBI in order to develop prevention strategies. [Figure: see text]
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Moroski, Nathan M., E. Lyle Cain, and Glenn S. Fleisig. "Assessment Of Functional Baseline And Return To Play Criteria Using Gps Profile." Orthopaedic Journal of Sports Medicine 7, no. 7_suppl5 (July 2019): 2325967119S0044. http://dx.doi.org/10.1177/2325967119s00441.
Full textAbstract:
Objectives: Return to play (RTP) are high following lower extremity injuries; however, objective sport specific clearance criteria are lacking. In ACL rehabilitation for example, current tests that are used such as single leg hop, isokinetic testing, and quad strength are not sport specific and do not take fatigue into account. With the development of wearable GPS technologies (Catapult), there is great potential for the creation of objective RTP criteria. These GPS units provide objective validated data points in regards to athletes and their movements during games, training, or rehabilitation. It is reported over 1,500 teams across 35 sports, including NFL, NBA, MLB, and NCAA, are now using this technology. Teams have a vast amount of information, however, it is largely underutilized by the medical staff, and no standardized benchmarks exist. Using this data it was our goal to establish baseline benchmarks for a variety of data metrics and to begin to establish validated return to play criteria. Methods: GPS records of a consecutive series of Division I NCAA football players were reviewed between 2015 and 2018. Ten metrics were gathered for healthy control players from eight positions (defensive back, wide receiver, running back, linebacker, tight-end, defensive line, offensive line, and quarter back. These metrics consisted of: total distance, total load, explosive yardage, explosive ratio, maximum velocity, inertial movement analysis (IMA) acceleration, IMA deceleration, change of direction (COD) left, and COD right. Average normal values were determined per session for healthy players. Overall we examined 198 player seasons data, 50 (DB), 37 (WR), 20 (RB), 47 (LB), 14 (TE) 14 (DL), 10 (OL), and 6 (QB) respectively. Results: Healthy control averages for total distance was 5456.9 yards (DB), 4973.8 yards (WR), 4260.5 yards (RB), 4054.8 yards (LB), 4334.2 yards (TE), 3498.1 yards (DL), 3274.7 yards (OL), and 4199.2 yards (QB) respectively. Average total load was 492.8 (DB), 463.8 (WR), 393.0 (RB), 367.0 (LB), 423.9 (TE), 389.7 (DL), 381.2 (OL), and 410.8 (QB) respectively. Average explosive yardage was 472.7 (DB), 605.1 (WR), 454.5 (RB), 190.1 (LB), 320.7 (TE) 107.5 (DL), 70.6 (OL), and 191.8 (QB) respectively. Average explosive ratio was 0.847 (DB), 0.855 (WR), 1.045 (RB), 0.989 (LB), 0.985 (TE) 1.53 (DL), 1.31(OL), and 1.66 (QB) respectively. Average maximum velocity was 18.3 (DB), 17.2 (WR), 17.4 (RB), 15.7 (LB), 16.1 (TE) 13.7 (DL), 12.0 (OL), and 16.6 (QB) respectively. Average acceleration was 9.27 (DB), 8.53 (WR), 9.13 (RB), 9.78 (LB), 12.01 (TE) 21.7 (DL), 16.5 (OL), and 47.1 (QB) respectively. Average deceleration was 6.11 (DB), 4.02 (WR), 4.74 (RB), 6.11 (LB), 5.68 (TE) 8.79 (DL), 9.12 (OL), and 1.25 (QB) respectively. Average COD towards left was 6.55 (DB), 7.24 (WR), 9.09 (RB), 6.98 (LB), 9.38 (TE), 13.4 (DL), 11.3 (OL), and 8.22 (QB) respectively. Average COD towards right was 5.80 (DB), 6.45 (WR), 7.84 (RB), 5.91 (LB), 6.74 (TE) 12.5 (DL), 10.7 (OL), and 6.62 (QB) respectively. Conclusion: With the established healthy averages we now have a starting point for comparison of injured athletes and their rehabilitation progress. Categories most closely correlating with return to play following specific injuries is the next step. Additionally, this information may be used in injury prevention, detecting when an athlete may be overly fatigued and at great risk for injury. More data is needed to validate these numbers as well as establish criteria for healthy return to play.
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Anderson, Matthew, Christina Mack, Mackenzie Herzog, William Levine, and Jamie Confino. "Poster 150: Defining the True Incidence of Glenohumeral Instability Among American Football Players: an Epidemiological Study of Non-missed-time Shoulder Instability Injuries in the National Football League." Orthopaedic Journal of Sports Medicine 10, no. 7_suppl5 (July 1, 2022): 2325967121S0071. http://dx.doi.org/10.1177/2325967121s00711.
Full textAbstract:
Objectives: Shoulder instability is a common injury among contact- and collision-sport athletes that encompasses a spectrum of glenohumeral pathology ranging from subluxation to dislocation. While glenohumeral dislocation frequently leads to removal from play, athletes are often able to play through glenohumeral subluxation. Previous research on glenohumeral instability among athletes has largely focused on missed-time injuries only, which has likely disproportionately excluded subluxation injuries and underestimated the overall incidence of shoulder instability. The objective of this study is to describe the epidemiology of shoulder instability injuries not resulting in missed time among professional athletes in the National Football League (NFL) during the 2015 through 2019 seasons. Methods: The NFL’s Electronic Medical Record was retrospectively reviewed to identify shoulder instability injuries that did not result in missed time during the 2015 through 2019 seasons. For each injury, player age, player position, shoulder laterality, instability type, instability direction, injury timing, injury setting, and injury mechanism were recorded. For injuries that occurred during games, incidence rates were calculated based on timing during the season as well as player position. The influence of player position on instability direction was also investigated. Results: During the 2015 through 2019 seasons, 546 shoulder instability injuries were documented in the NFL’s Electronic Medical Record. Of these, 162 (29.7%) did not result in missed time beyond the date of injury. The majority of non-missed-time injuries were subluxations (97.4%), occurred during games (70.7%), and resulted from a contact mechanism (91.2%). The overall incidence rate of game-related instability was 1.6 injuries per 100,000 player-plays and was highest during the postseason (3.5 per 100,000 player-plays). With respect to player position, the greatest number of non-missed-time instability injuries occurred in defensive secondary (28.4%) and offensive linemen (19.8%), while kickers/punters and defensive secondary had the highest game incidence rates (5.5 and 2.1 per 100,000 player-plays, respectively). In terms of direction, 54.3% of instability events were posterior, 31.9% anterior, 8.5% multidirectional, and 5.3% inferior. Instability events were most often anterior among linebackers and wide receivers (50% and 100%, respectively), while posterior instability was most common for defensive linemen (66.7%), defensive secondary (58.6%), quarterbacks (100.0%), running backs (55.6%), and tight ends (75.0%). Conclusions: Shoulder instability injuries that do not result in missed time beyond the date of injury are much more common among collision-sport athletes than previously thought, accounting for approximately 30% of all instability events in the NFL. The majority of these injuries are posterior subluxations, though instability direction appears to vary by player position. This study highlights the diverse nature of shoulder instability injuries and underscores the need for increased surveillance among collision-sport athletes, as even subluxations can result in significant damage to the capsulolabral complex. [Table: see text][Table: see text][Table: see text][Figure: see text]
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Schüler, Julia, Dagmar Wider, Dietmar Pfeifer, Martin Wagner, Heinz-Herbert Fiebig, and Monika Engelhardt. "Antitumor Activity in a Human Multiple Myeloma (MM) Model Using Sorafenib, Bortezomib, and Dexamethasone Treatment." Blood 112, no. 11 (November 16, 2008): 1720. http://dx.doi.org/10.1182/blood.v112.11.1720.1720.
Full textAbstract:
Abstract For a better understanding of myeloma disease and biology, the establishment of reproducible in vivo models is pursued worldwide. We have established a cell linebased, disseminated myeloma model in NOD/SCID-IL2-receptor-gamma-chain−/− (IL2−/−) mice. In the current study, this model was validated in various treatment groups, using 1. bortezomib (0.7mg/kg/day (d); d0, d4, d11), 2. sorafenib (200mg/kg/d; d0–11), 3. dexamethasone (3mg/kg/d, d0–4 + 7–11), in comparison with 4. a control group. L363 cells were injected intratibialy (it) into IL2−/− mice and respective therapies were started 7 days after L363-it-injection (d0). Tumor growth was monitored with daily monitoring of MM symptoms, fluorescence-based in vivo imaging (FI) performed every 2. week and flow-cytometry (FACS; detection of human HLA−A, B, C + CD138) performed once weekly by sacrificing 2 mice per group and analyzing bone marrow (BM), spleen, peripheral blood (PB) and liver. Based on the FACS data, tumor inhibition was calculated as the median percentage of MM cells at respective compartments of the test- vs. control-group multiplied by 100 (optimal test/control (T/C) in %). Furthermore, hollow bones of the injected mice were retrieved when mice were sacrificed for FACS analyses, cells flushed out and MM cells purified by MACS microbeads. Total RNA was isolated from these cells and gene expression profiles will be analyzed using the HG-U133 Plus 2.0 array (Affymetrix) and the Expressionist software (Genedata AG, Basel). L363 engrafted reliably (take rate=100%) at the injection site and in distant organs, such as BM (100%), spleen (38%) and rarely liver (8%). Control mice developed MM symptoms, such as hind limb pareses, weight loss and osteolyses. L363 cells were detected by FACS and FI, not only at injection sites, but also in the BM, hollow bones and spleen. Primary tumor development was markedly reduced by sorafenib (optimal T/C of 23% on d14), as well as with dexamethasone and bortezomib, albeit to a much lesser extend (optimal T/C: 81% + 62% on d14, respectively). BM metastases were also significantly reduced by sorafenib with an optimal T/C value of 67% on d28. Dexamethasone and bortezomib, the latter possibly due to subclinical doses (determined after titration and toxicity experiments), had no relevant influence on BM metastases suppression (97% + 100% optimal T/C on d28, respectively). Thus, L363 engraftment into IL2−/− is a valuable in vivo model for MM which exhibits high reproducibility, take- and metastases-rates and closely mimics the clinical situation. Collection of whole-body FI data proved to be a time- and animal-saving analysis that allows to closely monitor MM growth. Further investigations will validate the very promising antitumor activity of sorafenib and evaluate the potentially synergistic effect of bortezomib and sorafenib. Amongst others, a detailed characterization of the antitumor activity of both compounds will be provided by the gene expression profile of L363 cells isolated from untreated as well as treated mice. The evaluation of new therapeutic approaches in comparison to standard agents was thus successfully conducted, suggesting that our model serves as a valuable tool in the development of new anticancer strategies.
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Sistiarani, Colti, Bambang Hariyadi, Saudin Yuniarno, and Endo Dardjito. "Mother's Perspective About Using the Gadget Safeness for Children." JPUD - Jurnal Pendidikan Usia Dini 14, no. 2 (November 30, 2020): 313–20. http://dx.doi.org/10.21009/jpud.142.09.
Full textAbstract:
The rapid development of technology makes it easier for mothers to provide stimulation related to growth and development using gadgets. However, parental knowledge is needed about the safe limits of using a gadget in early childhood. This study aims to determine the perspective and behavior of mothers about the use of gadgets in toddlers. The method used is quantitative research with a cross-sectional approach. The participants of this study were thirty-one mothers who have early childhood and who are empowering family welfare. The inclusion criteria were mothers who agreed to be respondents, the exclusion criteria for mothers who did not have gadgets. This study uses a questionnaire measurement instrument for data collection. Data analysis was performed univariate and bivariate using the chi-square test. The results of the study concluded that the mother's knowledge regarding the safety of using a gadget was still lacking, with a value of around 54.8%, while the mother's behavior related to the same thing was better, which was around 58.1%. The relationship test shows that there is a strong enough relationship between maternal knowledge and maternal behavior in introducing or using gadgets in toddlers.
Keywords: Early Childhood, Mother Perspective, Gadget Safeness
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