Factors that influence ground reaction force profiles during counter movement jumping

BAKGROUND: The purpose of this study was to examine how hip, knee and ankle kinetics and kinematics influence effective impulse production during countermovement jumps. METHODS: Eighteen semi-professional soccer players (22.8 +/- 2.2 years) volunteered to participate in the study. Participants completed three maximal countermovement jumps on two force platforms (1000 Hz) that were linked to a nine camera infrared motion capture system (500 Hz). RESULTS: Kinetic and kinematic data revealed jumpers who fail to achieve uniform ground reaction force curves that result in optimal impulse production during their jump always display hip adduction and or hip internal rotation during the concentric phase of the countermovement jump. The variation of hip adduction and or internal rotation likely represents failed joint transition during the concentric phase of the countermovement jump and appears to account for a non-uniform force trace seen in these jumpers. CONCLUSIONS: The findings suggest rehabilitation and conditioning exercises for injury prevention and performance may benefit from targeting frontal and transverse plane movement.