Changes Of SEMG During The Isometric Contraction Of The Anterior Tibial Muscle Skin By Pre-cooling Stimulation At Different Time

Purposes: From the index of s EMG to study the effect of different time of pre-cooling stimulation on the skin while middle and low load exercise muscle recruit fast muscle fibers.Then determine the skin pre-cooling time at low load maximum recruit fast muscle fiber,and for strengthen muscles provides a new method.Methods: A total of 10 male and 6 female subjects,with a cold pack compress to the tibialis anterior muscle carrying on skin pre-cooling stimulation at different time(no pre-cooling,pre-cooling 1min,pre-cooling 3mins,pre-cooling 5mins,pre-cooling 7mins).After measure immediately skin temperature,and sitting posture straight knee boleos isometric exercise immediately for 1min with the load for 30%MVC and 55%MVC.Recording the change of the EMG signal,and measuring skin temperature again and recording the change of RPE value after the end of the exercise.The changes of RPE and electromyographic index RMS and MPF were analyzed with skin pre-cooling stimulation at different time.Results:(1)After middle and low load isometric exercise with skin pre-cooling stimulation the RPE value has a very significant difference(P<0.01),and between PC3~PC5 RPE value had the lowest value;(2)While middle and low load isometric exercise with skin pre-cooling stimulation,the RMS(%)value and MPF(%)value with significant difference(P<0.05).And through the double factor variance analysis,The RMS(%)value of males were affected by different skin pre-cooling time is greater than the exercise load;The RMS(%)value of females were affected by different skin pre-cooling time is similar to the exercise load.The MPF(%)value of male and female affected by different skin pre-cooling time were higher than the exercise load.(3)While the skin pre-cooling time of more than 3mins at L-PC the RMS(%)value is greater than M-NC for males;While for females need more than 5mins in L-PC.(4)The RMS value growth amplitude(%)increased with the increase of skin pre-cooling time,showing an inverted "U" type growth.The MPF decline amplitude(%)increased with the increase of skin pre-cooling time,showing an inverted "S" type growth.The changes of RMS and MPF were lagging behind 2~3min for female.Conclusion:(1)Before the middle and low load isometric contraction,the stimulation of 3~5min to the skin pre-cooling can help to prolong the movement time and prevent the increase of fatigue.(2)Before the middle and low load isometric exercise,as long as the skin pre-cooling stimulation can increase the RMS value,to recruit more fast muscle fibers to participate in activities.(3)Before the low load isometric exercise,the musle with skin pre-cooling stimulation 3~5min can achieve moderate load isometric exercise training effect.(4)Before the middle and low load isometric exercise,the best skin pre-cooling time is 3min for male,and 5min for female.