Changes Of SEMG Of Tibialis Anterior And Soleus Muscle Before And After Dorsiflexion Induced Fatigue

Purposes:By analyzing the characteristics of sEMG signal and action reaction time in the process of muscle fatigue induced by isometric contraction and its recovery,to evaluate the effect of fatigue on reaction time and muscle activation characteristics and its recovery law,and to provide theoretical basis for sports training and rehabilitation practice.Methods:The fatigue of tibial anterior muscle was induced by isometric contraction of ankle joint dorsiflexion(80%MVC).The sEMG signals of anterior tibial muscle(TA)and soleus muscle(SoL)during fatigue were recorded by surface electromyography,isokinetic muscle strength testing system and reaction time device,and the changes of maximum MVC of dorsiflexion and action response before and after fatigue and during fatigue recovery were analyzed.Results:(1)After fatigue,the relative peak torque values of dorsiflexion showed a gradual recovery trend.5 min,7 min,15 min,and 20 min were significantly higher than fatigue immediately(P<0.05),but did not return to the pre-fatigue level at 20 min.(2)After fatigue,the time domain index iEMG of tibialis anterior muscle increased significantly and the frequency domain index MF decreased significantly.When iEMG recovered to 7 minutes,there was a significant difference(P<0.05);after 10 minutes of fatigue,it gradually decreased,but did not return to the pre-fatigue level at 20 minutes.Except for the recovery period of 3 minutes,there were significant differences in MF between other periods and immediate fatigue(P<0.05).After 20 minutes of fatigue,MF recovered basically.(3)The change of the sEMG signal index of the soleus muscle was consistent with that of the tibialis anterior muscle.Immediately after fatigue,iEMG was significantly different from that before fatigue(P<0.05),and there was no significant difference between MF and pre-fatigue(P>0.05).iEMG showed significant difference(P<0.05)at 7min and 20min after fatigue,but did not fully recover;MF showed good regularity during recovery period,showing a gradual upward trend.After fatigue,the whole recovery period was compared with fatigue immediately.There was no significant difference(P>0.05),and it completely recovered to the pre-fatigue level 20 minutes after fatigue.(4)Immediately after fatigue,the ankle dorsiflexion RT increased significantly,with an increase of 46.90±16.12ms(P<0.05),and PMT and EMD accounted for 67%and 33%,respectively.During the fatigue recovery period,RT remained at a high level in the first 10 min(P>0.05),and the downtrend was obvious after 15 min,and returned to the pre-fatigue level at 20 min(P>0.05).(5)Immediately after fatigue,the ankle dorsiflexion RT increased significantly(P<0.05).During the fatigue recovery period,RT remained at a high level in the first 10 min(P>0.05),and the downtrend was obvious after 15 min,and returned to the pre-fatigue level at 20 min(P>0.05).(6)Immediately after fatigue,PMT and EMD of the tibialis anterior muscle were significantly increased(P<0.05).PMT remained at a high level 5 minutes before the recovery period,and decreased rapidly after 15 minutes,and returned to the pre-fatigue level after 20 minutes(P<0.05).The recovery period of EMD was relatively long,and remained at a high level at 15 min.After that,the downward trend was obvious,but it did not return to the pre-fatigue level at 20 min(P>0.05).(7)At the moment of fatigue,the soleus muscle PMT and EMD were both significant(P<0.05).PMT maintained at a high level 5 minutes before the recovery period,then decreased,and decreased significantly after 15 minutes,and returned to the pre-fatigue level after 20 minutes(P<0.05).There was no downward trend in the first 15 min of EMD,and then began to decline,but it did not fully recover at 20 min(P>0.05).Conclusions:(1)During the process of local muscle fatigue and recovery induced by isometric contraction,the activation degree of active muscle and antagonist muscle changes synchronously,and the co-activation ratio remains at a certain level.(2)During the recovery period of fatigue,the recovery degree of sEMG index iEMG is not consistent with that of MF,and the recovery rate of MF is faster than that of iEMG.(3)After exercise-induced muscle fatigue,RT and its components(PMT,EMD)were significantly prolonged.PMT contributed a lot to the fatigue effect,but its recovery time was short.