Study On The Effect Of Long Squat On Muscle Coordination And Jumping Force Of Lower Limbs

Objective：In the daily life and sports, the knee joint and surrounding ligaments playan extremely important role. And the co-activation of the lower limb muscle isimportant in the activities of knee joints and its ligaments. Previous studies haveshown that:the creep of anterior cruciate ligament and posterior cruciate ligament candecrease the co-activation of before and after muscle group and increase the strengthof agonist.But for a long time squats on muscle co-activation and jumping ability hasnot been studied.This topic is test the change of the lower limb muscle co-activationand muscular strength hrough long time squatting which affect the anterior cruciateligament of knee joint.This can provide certain theoretical basis to avoid injury andimprove performance.Methods:30graduate students male and female (each15)were selected as subjectswhich in good health and had no exercise injury of lower limbs for this study.Measuring changes in left and right sides of rectus femoris and posterior bicepsfemoris muscle activity.Using the German Biovision multi-channel surface EMGacquisition muscle activity of Static lower limb in Flexion and extension conditionand lower limb muscle do CMJ and SJ movement condition in3-D Kistler forceplatform. At the same time use digital cameras record the entire bounce process. Byanalyzing the data to compare the change of muscle strength and itscoordination before and after the long time squat.Results：After long time squats, the co-activation of lower limb muscles are rising in extensor andflexor phase from static stretch action, respectively from0.09(0.06)(M (SD))and0.25(0.13) to0.11(0.10) and0.10(0.40).In extensor phase of Countermovement jump and Squat jump, thelower limb muscle co-activation respectively from0.50(0.30) fell to0.37(0.18), decreased from0.33(0.13) to0.28(0.11), P<0.05.But in flexor phase of Countermovement jump, theco-activation of lower limb muscles is from3.28(2.78) to3.28(3.18), and P <0.05. In jumpingability, bounce strength in jumping ability (FZ) is from788.15(226.12) N to788.86(267.66) N,and jumping height is from3.31(0.07)m down to3.30(0.08)m. Conclusions and suggestions: After long time squats, in static stretch action, there are nosignificant changes in the co-activation of lower limb muscles, but slightly larger values;TheCountermovement jump, lower limb muscle co-activation have significant increase and decreaserespectively in extensor and flexor phase;In the process of squat jump, whether male or female,lower limb muscle has a significant decrease of co-activation;Bounce strength and height there isno significant change.From squat for a long time, therefore, the creep and anterior cruciateligament, the creep disappear from the antagonist protective reflex arc, increase the risk ofinjury.So, in the life and soprts should avoid the squat for a long time, and should be standing orrest to restore ligament after a period of time, prevent to produce ligamentous laxity.