Effect Of Exercise-induced Muscle Fatigue On Anticipatory And Compensatory Postural Adjustments Of Trunk Stabilizer Muscles

Background: Anticipatory postural adjustments(APAs)and compensatory postural adjustments(CPAs)are the early postural mechanisms initiated by the central nervous system(CNS).They play a crucial role in postural maintenance,postural orientation,and movement performance when in response to self-induced or externally triggered postural perturbations.Exercise-induced muscle fatigue is theorized to deteriorate postural control by its adverse effects on the sensitivity of sensory receptors,the efficacy of contractile properties,and neuromuscular control.To the best of our knowledge,the effect of exercise-induced muscle fatigue on early postural control mechanisms and postural stability is not yet well understood.Objective: The purpose of this study was to explore the effect of exercise-induced muscle fatigue on the early postural control mechanisms and postural stability.We took the trunk stabilizer muscles as the object of observation.From two perspectives of early postural control and non-exercised postural muscle,at the three fatiguing conditions of joint,limb,and whole-body exercise,we compared the effect of knee extensor and flexor fatigue,unilateral and bilateral lower limb fatigue,local and general fatigue,and the subjects with or without long-term training experience on the APAs and CPAs activation organizations of trunk stabilizer muscles as well as postural stability.Method: To explore the effect of muscle fatigue on early postural control mechanisms,research 1 to 3 compared intermittent isometric knee extension and flexion;unilateral and bilateral leg-press;knee extension and rowing ergometer exercise,respectively.Before and immediately after the fatiguing exercise,the center of pressure(COP)-based postural stability measures during quiet stance and electromyography(EMG)-based APAs/CPAs measures during fast arm–raising movements were recorded.To investigate the effect of long-term training experience on postural control,research 4compared the APAs/CAPs and COP measures before and after the rowing ergometer fatigue in trained and untrained subjects.Result:(1)Knee extension and flexion fatigue resulted in an earlier anticipatory onset of TrA/IO,larger APAs coactivation of TrA/IO–LMF,and unchanged CPAs and COP measures.(2)Unilateral and bilateral lower limb fatigue increased postural sway and CPAs coactivation of TrA/IO–LMF but did not affect APAs.Under fatigue condition,the bilateral than unilateral group swayed faster and longer and activated the anticipatory onset of TrA/IO earlier.(3)General fatigue had a further effect on COP measures than local fatigue.Under fatigue condition,the local group activated an earlier anticipatory onset of LMF,with larger APAs coactivation of TrA/IO–LMF and smaller CPAs activation of TrA/IO than the general group.(4)After general fatiguing exercise,the untrained group activated larger CPAs coactivation of TrA/IO–LMF.Furthermore,regardless of fatigue conditions,the trained group exhibited an earlier anticipatory onset of trunk stabilizer muscles,larger APAs and CPAs activation of LMF,and larger APAs coactivation of TrA/IO–LMF than the untrained group.Conclusion: Lower limb muscle fatigue can trigger the trunk stabilizer muscles' early posture control mechanisms to maintain postural stability.(1)Knee extensor and flexor muscle fatigue can induce the APAs control mechanism of the trunk stabilizer muscles.(2)Unilateral or bilateral lower limb fatigue can trigger both the APAs and CPAs control mechanisms of the trunk stabilizer muscles.(3)Whole-body exercise-induced muscle fatigue can trigger the CPAs control mechanism of TrA/IO;(4)The trained group sway less than the untrained group after fatigue.However,regardless of fatigue conditions,the trained group activated more efficient APAs and CPAs control mechanisms of the trunk stabilizer muscles than the untrained group.It suggests that long-term training experience can update and facilitate postural control efficiency.