Correlation Between Body Weight and Eccentric Hamstring Strength in American Football Players

Hamstring strength and explosiveness is imperative for collegiate American football players to perform at the highest level. Understanding the respective correlations, based on players positions, between eccentric hamstring strength (HS) and body weight (BW) among football players may help coaches and players to develop strength protocols required for specific positions. We hypothesize that increasing BW will result in increased eccentric HS. PURPOSE: This study aims to examine the relationship between football players BW and their max eccentric HS. METHODS: As a secondary analysis from the HAMIR study, 95 (age: 21.4 ± 2.00 yr; Ht: 187.7 ± 6.17 cm; Wt: 102.4 ± 17.9 kg) actively rostered and uninjured Division I football players participated in the study and were grouped by position: the big group (OL & DL) (age: 21.6 ± 1.78 yr; Ht: 192.2 ± 5.77; Wt: 122.5 ± 16.1 kg), the combo group (TE & LB) (age: 21.6 ± 2.08 yr; Ht: 189.2 ± 4.42 cm; Wt: 107.0 ± 4.45 kg), and the skills group (DB, K, WR, QB, & RB) (age: 21.2 ± 2.09 yr; Ht: 184.3 ± 5.13 cm; Wt: 88.5 ± 7.70 kg). Athletes were weighed and then max eccentric HS was measured as each participant performed three Nordic curls on a Nordbord device. The average max force exerted from the right and left leg from 3 trials was recorded for data analysis. RESULTS: Overall, we noted a weak correlation between players BW and their max eccentric HS (r = 0.34, p = <0.0008, Force: 451.6 ± 83.5 N). However, both the combo and skills group showed moderate correlation respectively (r = 0.57, p = <0.006, Force: 476.1 ± 63.8 N; r = 0.37, p = <0.01, Force: 433.0 ± 68.2 N). The big group showed a weak correlation (r = 0.31, p = <0.12, Force: 463.3 ± 112.3 N). CONCLUSION: The observed positive correlation confirms our hypothesis that larger players would have greater eccentric HS. The moderate correlation in the combo and skills group implies that BW does affect football players eccentric HS. This finding is important because it supports the coaching stance that collegiate football players' strength enhances with weight gain. However, in the largest players this correlation was weaker. This weaker correlation shows that increasing BW alone does not fully indicate increasing eccentric HS. Thus, other factors such as adipose tissue gain, or larger bone mass need to be considered when assessing eccentric HS in relation to BW.