Relationship of Reactive Strength to Body Composition Measures in Elite American Football Players

Relationship of Reactive Strength to Body Composition Measures in Elite American Football Players

Reactive strength (RS) represents function of a muscle’s stretch shortening cycle, or the ability torapidly change from an eccentric contraction to a concentric contraction. RS is important in sports requiring explosive movements such as cutting, jumping, sprinting, and is commonly a focus of strength and conditioning programs. RS may be influenced by body composition as lighter mass basketball players have shown superior RS over higher mass players. This relationship in elite American football players in unknown. Therefore, the purpose of the study was to determine if body mass (BM), lean body mass percent, (LBM), or fat mass percent (FM) were associated with RS during a drop jump (DJ) in elite American football players. Twenty-five males (age, 22.3+0.09 yrs; ht, 186.02+8.54 cm) undergoingtraining for the National Football League’s combine draft volunteered for this study. Body compositionvariables were obtained via BodPod, and RS was calculated using the RS index (RSI=jump ht/contact time) using a timing mat during a 60 cm DJ. Pearson Correlation Coefficients were used to determine three associations; (a) RSI and BM, (b) RSI and LBM, and (c) RSI and FM, p<0.05. Results showed significant negative correlations between RSI (1.26+0.40) and BM (100.81+14.04 kg), and LBM (85.32+8.24 %), r=-0.397, p=0.050 and r=-0.565, p=0.003, respectively. RSI was not significantly associated with FM (15.72+4.97 %; r=-0.248, p=0.231). Players who were heavier and players who possessed a greater amount of LBM had lower RS than lighter players and those with less LBM. Explosiveness appears to be related to heaviness.