Research Of Fatigue Related Association Between Agonistic, Antagonistic Muscle SEMG And EEG

Objective:The objective of this study is to explore the function connection and thecharacteristics of common neural inputs to co-contracting antagonistic elbow musclesduring sustained isometric fatiguing contraction, basing on examining fatigued relatedtime, frequency and phase association between agonistic, antagonistic muscle SurfaceElectromyogram Signal and EEG, and observing the influence of antagonistic muscleprefatigue on sEMG and EEG in later muscle contraction.Methods:Fifteen young male volunteers participated in this study. Each subject sustainedisometric elbow flexion at20%and60%maximal level until exhaustion while theirbrain (EEG) and brachioradialis muscle(BR), biceps brachii muscle(BB), tricepsbrachii muscle muscle(BB)(sEMG) activities were recorded. Besides, EEG andsEMG was recorded during elbow extension before and after prefatigue ofantagonistic muscle. The entire elbow flexion fatigue contraction duration of the EEGand sEMG recordings was divided into the first half (stage1) and second half(stage2).Cross correlation, coherence and phase synchronization index of stage1and stage2were observed. Influence of antagonistic muscle prefatigue on sEMG indices andsEMG coherence were also observed and analyzed.Results:(1)The average power of both EEG and EMG increased significantly in stage2compared with stage1at theta, alpha and beta frequency band. Average and relativepower of sEMG and EEG all increased at beta frequency band.(2) In20%MVC elbow flexion, sEMG-EEG Coherence increased significantly instage2compared with stage1in alpha frequency band.(3) In20%MVC elbow flexion, phase synchronization index of BR sEMG-EEG inbeta frequency band, BB sEMG-EEG in theta and alpha frequency bands, TBsEMG-EEG in theta, alpha, gamma frequency bands all increased in stage2comparedwith stage1at alpha. In60%MVC elbow flexion, phase synchronization index of BRsEMG-EEG in gamma frequency band, BB sEMG-EEG in theta frequency band, TBsEMG-EEG in theta, alpha, gamma frequency bands increased in stage2comparedwith stage1.(4) Phase synchronization index in alpha, gamma frequency bands betweensynergistic muscles and antagonistic muscles increased in stage2compared withstage1at alpha and beta frequency band in20%MVC elbow flexion. In60%MVCelbow flexion, phase synchronization index of BB-TB in theta, alpha, beta frequencyband and phase synchronization index of BR-BB,BR-TB in beta frequency band were increased in stage2compared with stage1.(5) Coherence of BR-BB sEMG in beta frequency band and coherence ofBB-TB,BR-TB in beta and gamma frequency band were increased in stage2compared with stage1during20%MVC elbow flexion. In60%MVC elbow flexion,coherence of BB-TB in beta frequency band increased significantly in stage2compared with stage1.(6) sEMG-sEMG coherence in beta frequency band after antagonistic muscle fatiguecaused by20%MVC isometric contraction increased compared with coherence beforeantagonistic muscle prefatigue. C(n) of TB decreased significantly after antagonisticmuscle prefatigue caused by20%MVC isometric contraction increased comparedwith coherence before antagonistic muscle prefatigue. sEMG-sEMG coherence intheta frequency band after antagonistic muscle prefatigue caused by60%MVCisometric contraction was significantly different from coherence before antagonisticmuscle prefatigue.Conclusions:(1) Coherence and phase synchronization association of synergistic muscles andantagonistic muscles and agonistic muscle, antagonistic muscle and motor cortexcoupling had consistency changes caused by exercise-induced muscle fatigue, whichsupports the notion of a "common drive" in antagonistic muscles control.(2) Fatigue cause brain and muscle activities and the coupling of motor cortex andperipheral muscles all increased. In order to maintain the target force and jointstability, antagonistic muscles are coordinated to activate in a more synergisticmanner.(3) sEMG-sEMG coherence in beta frequency band of antagonistic muscles decreasedcaused by antagonistic muscle fatigue, indicating that the common neural inputs toantagonistic muscles decreased. It might be related to asynchronism change ofagonistic and antagonistic muscles in peripheral and central region, mutual influencesof antagonistic corticospinal neurons as they are closely grouped or intermingled, anddifferent motor unit recruitment patterns adopted to coordinate agonistic andantagonistic muscle activity in order to maintain joint stability.