Eccentric Hamstring Strength By Position For Division 1 Football Athletes

Hamstring strain injuries are prevalent in collegiate football, with eccentric hamstring strength being a common target of injury mitigation programs. Eccentric hamstring strength is commonly assessed during the Nordic hamstring exercise; however, there are no known normative values for collegiate football players with consideration of the athletes’ position. Given the position-specific demands of the sport, typical eccentric hamstring strength is likely to vary by position. PURPOSE: To characterize eccentric hamstring strength by position in Division 1 football athletes. METHODS: Eccentric hamstring strength during the Nordic hamstring exercise was measured prior to the start of the fall season. Three maximum effort trials were performed and the peak force from each limb across all trials was utilized for analysis. Between-limb force asymmetry was calculated as the absolute difference between limbs divided by the average across limbs. Linear mixed effect models were used to calculate least square means and 95% confidence intervals of peak force (N and N/kg body mass) and force asymmetry by player position and position group, accounting for repeated measures. RESULTS: 321 male football athletes (age: 20.4 ± 1.6 yr) completed 560 preseason eccentric hamstring strength assessments. Athletes repeated tests up to four times with a median of one test per athlete (interquartile range: 1-2). Normative eccentric hamstring strength differed by position (see table). Between-limb force asymmetry was similar across positions. Linemen displayed the greatest peak force, while running backs and wide receivers had the greatest peak force when adjusted for body mass. CONCLUSIONS: These values provide initial guidelines for assessing expected peak force and between-limb force asymmetry during the Nordic hamstring exercise for Division 1 football athletes by position. ACKNOWLEDGEMENT: This work is supported by a research grant from the National Football League. - Table. Body mass, peak force, normalized peak force, and between-limb force asymmetry by position and position group for football athletes Position (N) Body Mass (kg) (SD) Peak Force (N) (95% CI) Normalized Peak Force (N/kg) (95% CI) Force Asymmetry (%) (95% CI) Position Group (N) Body Mass (kg) (SD) Peak Force (N) (95% CI) Normalized Force (N) (95% CI) Force Asymmetry (%) (95% CI) DL (40) 128.7 (13.9) 515 (494, 535) 4.04 (3.84, 4.23) 6.2 (4.3, 8.0) Big (88) 130.7 (14.6) 505 (492, 519) 3.91 (3.78, 4.04) 7.0 (5.8, 8.3) LS (7) 104.7 (6.9) 459 (413, 506) 4.40 (3.94, 4.85) 9.4 (4.9, 14.0) OL (41) 130.4 (10.1) 505 (485, 524) 3.71 (3.52, 3.90) 7.5 (5.7, 9.3) LB (52) 104.2 (7.2) 455 (438, 473) 4.38 (4.20, 4.55) 7.1 (5.5, 8.7) Power (95) 104.2 (8.0) 470 (457, 483) 4.51 (4.39, 4.65) 7.9 (6.7, 9.1) RB (25) 101.0 (8.3) 496 (471, 522) 4.93(4.68, 5.18) 8.0 (5.6, 10.3) TE (18) 109.0 (7.5) 477 (446, 508) 4.38 (4.08, 4.68) 10.2 (7.6, 12.8) DB (64) 87.2 (8.9) 423 (406, 440) 4.86 (4.70, 5.03) 9.8 (8.3, 11.3) Skill (111) 86.5 (8.8) 421 (409, 434) 4.88 (4.76, 5.01) 9.8 (8.6, 10.9) WR (47) 85.6 (8.6) 419 (400, 438) 4.91 (4.73, 5.10) 9.7 (8.0, 11.4) QB (14) 95.3 (7.8) 412 (378, 445) 4.32 (4.00, 4.65) 7.6 (4.3, 10.8) Special (29) 93.5 (10.5) 424 (401, 447) 4.58 (4.36, 4.81) 7.7 (5.5, 9.9) K/P (15) 92.1 (12.1) 434 (404, 465) 4.79 (4.50, 5.09) 7.9 (4.8, 10.9) SD: standard deviation; CI : confidence interval; DL: defensive line; LS: long snapper; OL: offensive line