Relationship Between Bone Length Ratio Of Lower Limbs And Surface EMG Characteristics Of Squatting Lower Limb Muscles

Purposes:Carry out surface electromyography(EMG)experiment of squat movement,correlation analysis was used to investigate the relationship between the length characteristics of individual lower limb bones and the surface EMG activation of lower limb muscles under different load and different action repetition times during squatting.At the same time,the regulatory effects of load factors and action repetition times on the surface EMG activation of lower limb muscle groups in squatting were investigated,thus expounds the problem categories to be dealt with in the future training practice.Methods:25 ordinary female college students were recruited,use calculation method to Pretest the subjects’ maximum strength level of squat,femur data were collected by X-ray,tibial data were collected by bone marker caliper.Before the formal squat test,the surface EMG equipment was posted on the main muscle group of the lower limb on the dominant side,Subjects were asked to follow a uniform pattern of squatting movements and follow the rhythm of the metronome to complete them in sequence,the sequence is 6 self-weight squats,8 self-weight squats,6 75%RM load squats and 8 75%RM load squats.After the test,paired sample t-test and related sample non-parametric test were used to compare the differences of muscle RMS levels under different load and different action repetition times,correlation analysis was used to infer the relationship between the proportion of legs and the proportion of lower limb muscle activation.Results:(1)In this research,there is no significant correlation between the length ratio of individual legs and the EMG RMS ratio of the main muscle groups of individual lower limbs during squatting(p<0.05);(2)Under the same number of repetitions,the RMS value of the surface electromyography of the main muscles of the lower limbs in 75%RM load squats is much higher than that in self-weight squats(p<0.05);(3)Under load,the surface EMG RMS value of rectus femoris squatting 6 times in a single group is slightly higher than that of squatting 8 times in a single group(p<0.05),the RMS of other test muscles only shows a downward trend with the increase of action repetition,but it has no statistical significance(p>0.05).When squatting with self-weight,there was no significant difference between the surface EMG RMS value of all muscles in a single group squatting for 6 times and that in a single group squatting for 8 times(p>0.05);(4)Under any repetition number or load involved in the experiment,the surface EMG RMS value of the single joint muscle represented by "medial femoral muscle" and"lateral femoral muscle" in the front of the femur is always higher than that of the single joint muscle represented by "gluteus maximus" in the back of the femur.However,before and after femur the surface EMG RMS values of double joinit muscles represented by "rectus femoris","biceps femoris" and "semitendinosus" do not have a unified bias,despite there are some individual differences exist,but as a whole,the comprehensive surface EMG RMS value of the anterior main muscle group of femur is always significantly higher than that of the posterior muscle group;(5)When self-weight squat,the RMS ratio of single joint muscle group,double joint muscle group and Anterior/posterior femoral muscle group has no significant difference in the comparison of 6 or 8 repetitions difference(p>0.05).However,in load squat,with the increase of the number of repetitions,the contribution ratio of posterior femoral muscle RMS increased(p<0.05).If with the same number of repetitions,although the absolute RMS volume increase in the posterior femoral muscle group is smaller than that in the anterior femoral muscle group,but the posterior muscles will show higher magnification(p<0.01).Conclusions:(1)Current evidence suggests,the individual specific bone length ratio of lower limbs cannot directly determine and explain the potential bias of the activation degree of main muscle groups of lower limbs in squatting;(2)Under the same number of repetitions,increasing load can effectively improve the activation level of main muscle groups of lower limbs during squatting;(3)In self-weight squat,adjusting 6 or 8 repetition in a single group movement has little effect on the activation of the main muscle groups of the lower limbs.Under the condition of 75%RM load squat,if adjust the number of action repetitions in a single group,the degree of muscle activation decreases with the increase of action repetitions.However,in our scheme,except rectus femoris,the influence on other muscles is not obvious;(4)When squatting,the activation degree of single joint muscle in the front of femur is the highest,the activation degree of double joint muscles before and after femur is affected by weight or other factors,so there is no specific bias,the overall activation degree of anterior femoral muscle group is always higher than that of posterior femoral muscle group;(5)In self-weight squat,adjusting the number of repetitions will not have a significant impact on the activation ratio of lower limb single joint muscle group,double joint muscle group and Anterior/posterior femoral muscle group.However,with the increase of the repetitions,the activation proportion of posterior femoral muscle will increased synchronously,under the same number of action repetitions,compared with the self-weight condition,although the absolute volume of the activation degree of the posterior femoral muscle group caused by load factor is smaller than that of the anterior femoral muscle group,the activation enhancement effect of the posterior femoral muscle has a higher magnification.