The Biomechanical Influence Of Fatigue On The Lower Exteemity Of Volleyball Block Jump Movements

Objective: Epidemiological studies have shown that fatigue is an important reason for declining movement ability and increasing damage.Previous research on the definition of fatigue degree and the variety of fatigue index are quite different.The main objective of this study was to compare the lower limb motor performance or technical strategy of changing characteristics when participants complete the vertical jumping action of blocking under no-fatigue,moderate fatigue,and severe fatigue in fatigue levels,with increasing fatigue.Analysis of biomechanics changes on takeoff caused by fatigue effects and the effects of injuries.So it can provide a theoretical basis developing training plans for volleyball players,and improve performance and reduce injury.Methods: 10 subjects were Beijing sports University men's varsity volleyball players.Respectively,without fatigue,fatigue and severe fatigue State of three vertical jumping action of blocking tests.Using high speed motion capture system and force plate to acquire data of kinematics and dynamics.Results: With increasing fatigue,the time and height of the flight phase was reduced.the flight time,height of Severe fatigue was less than moderate fatigue and no-fatigue(P<0.05).The buffer length,hip ROM significantly of moderate and severe fatigue in Buffer stage was less than no-fatigue(P<0.05),the knee ROM of severe fatigue significantly less than no-fatigue(P=0.015),and ankle ROM of severe fatigue was significantly less than the degree of moderate fatigue(P=0.012).In Stretch phase,the time,vertical displacement of the center of gravity,hip and knee ROM,stretch impulse of moderate and severe fatigue was less than no-fatigue state(P<0.05).The ankle ROM,peak of hip and knee angular velocity of severe fatigue was less than the degree of moderate fatigue and no-fatigue.The ROM of hip,knee and ankle in landing stage was increasing from no-fatigue to moderate fatigue,but declining from moderate fatigue to no-fatigue.Conclusions: 1.With the increase of fatigue,the range of flexion and extension of the lower extremity joint in the taking-off buffer phase gradually decreased.2.With the increase of fatigue,the range of flexion and extension of the lower extremity joint and the angular velocity of the lower limb pedal extension step are gradually reduced,and the pedaling time is shortened,thus reducing the take-off effect.3.With the increase of fatigue,the flexion angle of the knee joint decreases at the peak of the ground and vertical ground reaction in the landing stage,which increases the risk of injury of the anterior cruciate ligament.4.Fatigue increase does not have a significant effect on the vertical ground reaction force peak and its loading rate in the landing stage.