Association Between Morphology Of NFL Draft Hopefuls And Running Kinetics: Implications For Knee Osteoarthritis Development

Size is prized in American football with as many as 97% of players categorized as overweight and 56% as obese. Overweight and obesity are risk factors for knee osteoarthritis (OA) and have been linked to high knee adductor moments (KAM) and vertical ground reaction forces (vGRF) during gait. Knee OA is more prevalent in retired players than in the general population and warrants investigation. Minimal attention has been given to the study of football activity kinetics in current players which could provide valuable prospective insight to knee OA development. PURPOSE: To examine the association between morphology of American football players and select knee and ground reaction forces during high-speed running. METHODS: 54 American football players (age, 22.8 ± 1.1 yrs; height, 185.6 ± 5.7 cm) from a professional draft preparation camp underwent body composition measurement using bioelectrical impedance and performed a 5-sec run at 5.5-6.5 m/s on an instrumented treadmill synchronized with 10-camera motion capture. Pearson Correlation Coefficients were used to evaluate the association between total body mass (TBM; kg), lean body mass (LBM; kg) and body fat percent (BF; %) with normalized peak knee adductor moments (KAM; Nm/kg), peak knee compression joint reaction forces (KJRF; N/kg) average vertical ground reaction forces (vGRF; N/kg) during running, p < 0.05. RESULTS: TBM (96.1 ± 13.8 kg) was negatively associated with KAM (22.5 ± 4.6 Nm/kg; r = -0.322), vGRF (18.5 ± 1.3 N/kg; r = -0.537), and KJRF (25.1 ± 2.1 N/kg; r = -0.379), p < 0.05. LBM (85.0 ± 9.9 kg) was also negatively associated with KAM (r = -0.338), vGRF (r = -0.545), and KJRF (r = -0.429), p < 0.05. BF (11.9 ± 5.7 %) was only associated negatively with vGRF (r = -0.315), p < 0.05. As player TBM and LBM increased, normalized KJRF, KAM and vGRF decreased. CONCLUSION: During a single bout of high-speed running, heavier players appear to module knee and ground kinetics by producing less per kg than lighter players. Results may be used to prospectively track player knee health.