Muscle Fatigue and Injury in Exhaustive Stretch-shortening Cycle Exercise and the Lower Limb Joint Power Contribution in Eccentric and Concentric Concentration Phase

Objective:The purpose of the present study is to investigate the effect of muscle fatigue and injury and lower limb joint power contribution after exhaustive stretch-shortening cycle(SSC) exercise,so as to supply some reference for training and prevention.Methods: 11 healthy male volunteers participate in the SSC fatigue model,assesses characteristics of fatigue and injury in eccentric and concentric phase via EMG,joint contribution and joint peak power in eccentric and concentric phase.Results 1) Muscle concentric performance decreases immediately after exhaustive SSC,recovers within 10min and remains at the same level follow up 2 and 4 days.However,recovery delays after eccentric contraction.2) Knee joint endures the heaviest loads in aforementioned exercise model. 3) EMG and CK activity shows delayed recovery symptom after eccentric contraction of SSC.Conclusion: Eccentric contraction in exhaustive SSC induces DOMS obviously,and recovers slowly.However,there's no obvious DOMS or injury symptom after concentric phase.Knee joint extensors are the main generators during SSC,and the hip and ankle joint contribution increases so as to compensate for the lost knee joint function.All of aforementioned points make up of coordinate mechanism of lower limb.