Effects Of Unilateral And Bilateral Lower Limb Fatigue On The Posture Stability And Posture Adjustments

Background:Posture control(PC)is a series of neuromuscular motion control activities and processes,which are accomplished by the posture control system(PCS)to stabilize the center of gravity and position the limbs in space.It has the characteristics of cross control and overall coordinated control.Current studies have found that exercise-induced muscle fatigue has a significant impact on body posture stability and motor performance,but its mechanism is not fully clear.This study will research the effect of lower limb muscle fatigue on body posture stability and its mechanism based on the anticipatory posture adjustments(APAs)and compensatory posture adjustments(CPAs)mechanisms.Objective:This study aims to observe the influence of exercise-induced muscle fatigue on the posture stability and its APAs and CPAs mechanisms,which provides a scientific theoretical basis for the theoretical study of posture control in sports physiology.Methods:Two-factor experiment was designed in experiment 1,the fatigue pattern of lower limb muscles(2)×the fatigue state of lower limb muscles(2).Fourteen young male subjects completed the single-leg and double-leg pedal exercises loading tests respectively.The effects of lower limb muscle fatigue on RPE and MVC of lower limbs were observed.The changes of COP were measured by AMTI force platform to investigate the effect of lower limb muscle fatigue on MVC.Two-factor experiment was designed in experiment 2,the fatigue pattern of lower limb muscles(2)×the fatigue state of lower limb muscles(2).Fifteen young male subjects completed the single-leg and double-leg pedal exercises loading tests respectively.The effects of lower limb muscle fatigue on RPE and MVC were observed.The effects of lower limb muscle fatigue on APAs response time,APAs response intensity and CPAs response intensity were observed by postural adjustment method induced by external postural perturbation.Results:(1)Unilateral and bilateral lower limb pedal fatigue test resulted in a significant increase in RPE(p=0.000),with no significant statistical difference between them;lower limb MVC decreased by 16.9%and 30.0%respectively,with significant statistical difference between them(p=0.002);COP ellipse area(p=0.031)and trajectory length increased significantly(p=0.001),and there was no significant difference between fatigue patterns;(2)Unilateral and bilateral lower limb pedal fatigue test resulted in a significant increase in RPE(p=0.000),with no significant statistical difference between them;lower limb MVC decreased by 16.3%and 30.0%respectively,with significant statistical difference between them(p=0.002);The APAs reaction intensity of rectus femoris caused by fatigue(p=0.010),and The CPAs reaction intensity of tibialis anterior muscle(p=0.018)and rectus femoris muscle(p=0.008)increased,but the effects of unilateral and bilateral muscle fatigue on APAs reaction time,APAs reaction intensity and CPAs reaction intensity of tibialis anterior muscle and rectus femoris muscle were not significantly different.Conclusion:(1)Muscle fatigue of bilateral lower extremities resulted in a greater decrease in MVC of lower extremities pedaling than that of unilateral lower extremities.However,there was no significant statistical difference in the effect of static posture stability,showing a significant "bilateral effect";(2)Unilateral and bilateral lower extremity muscle fatigue can increase the APAs reaction intensity of rectus femoris muscle,and increase the CPAs of anterior tibial muscle and rectus femoris muscle,but there is no significant difference in APAs reaction time,APAs reaction intensity and CPAs reaction intensity between the two muscles,which shows the typical characteristics of "bilateral effect".