The Knee And Ankle Flexor\Extensor Muscles' Standardization Studying Of Surface Electromyography (sEMG)

Propose: Isokinetic muscle force testing,surface electromyography(sEMG)technology play an important role in rehabilitation care,sports training,sports science and medical fields.This research was designed to obtain the relationship between the isokinetic muscle force of flexor and extensor(gastrocnemius and tibialis anterior muscle,femoral rectus and biceps femoris)in lower limbs and sEMG,which can illustrate the necessity of standardization of sEMG in evaluating muscle force directly.By comparing values of sEMG parameters between different muscles of the same muscle or different persons before and after standardization,we can confirm which type of exercise to evaluate muscle force is more effective as a normalized value.Method: In this research,we obtain the sEMG values of 12 XPEU male students' surface electromyography and muscle torque values of the 4 flexor and extensor muscles(gastrocnemius lateral,tibialis anterior muscle,femoral rectus,biceps femoris)in right lower limbs knee and ankle,which are in different contract form(maximal voluntary isometric contraction(MVIC))and different velocity(60°/s,180°/s)of contraction,by using high-speed photography,surface electromyography measurement and isokinetic muscle strength test.Results:(1)In the same muscle contraction process,the trend of muscle torque value and MA(mean amplitude)show a high degree of correlation and the correlation coefficient r is more than 0.6.(2)In different form and velocity of contraction,the muscle peak torque decreases with increasing velocity.When the muscle in ankle contracts centripetally at the same speed 60°/s,180°/s,there exists a significant difference between the muscle peak torque and the MVIC muscle peak torque(P<0.01,P<0.05).While measuring the muscle in knee,this situation is the same(P<0.05,P<0.05).Besides,the ratio of flexor and extensor peak torque values in knee and ankle is different significantly.(3)In different form and velocity of contraction,the values of RMS and iEMG decreases with the increasing velocity.When the muscle in ankle shrinks centripetally at the same speed 60°/s,180°/s,there exists a significant difference between the RMS and the RMS of MVIC(P<0.01,P<0.01;P<0.05,P<0.01),while the iEMG and the iEMG of MVIC is as well(P<0.01).The same situation occurs in the muscle in knee(P<0.01).In the same contraction form,comparing the flexor and extensor in ankle,it shows that the RMS and iEMG of extensor are less than flexor and the difference is significant(P<0.01).While in knee,the RMS value of MVIC of extensor is less than flexor,the difference is significant(P<0.05).At the same speed 60°/s and 180°/s,RMS of extensor is larger than flexor,the difference is significant(P<0.05);in MVIC and 180°/s contraction,the iEMG value of extensor is larger than flexor,the difference is significant(P<0.05),while in 60°/s contraction,the iEMG value of extensor is less than flexor,the difference is significant(P<0.05).(4)In deep jump,there is a significant change in the sEMG of the lower limb muscle before and after the standardization.After standardize the RMS and iEMG of the flexor and extensor in ankle,There is no significant difference between the normalized value of the constant velocity of 60 ° / s and the normalized value with MVIC as the standard(P>0.05).But The difference between the normalized value at a constant speed of 180 ° / s and the normalized value with MVIC is very significant(P<0.01).For the muscle in knee,both exist significant difference(P<0.01).(5)In deep jump process,the sEMG value after standardizing of lower limbs is relate to the velocity of rise.The maximum correlation appears between the standard valus of MVIC and velocity.While the values of 60°/s and 180°/s contraction are also relate to the velocity,and the degree of correlation is not high,especially in the 180°/s contraction,it may have no relationship.Conclusions:(1)Different contraction form and velocity,in the case of maximum muscle force,muscle torque and sEMG value of the trend was highly positive correlation: Muscle force during muscle contraction is consistent with MA;the muscle peak torque value,RMS and iEMG is largest in MVIC,and in constant speed centred motion,the muscle peak torque value,RMS and iEMG decreases with the increasing velocity.(2)Comparation of flexor and extensor,both in knee and ankle,the peak torque value of extensor is larger than flexor;the RMS and iEMG of extensor in knee are larger than the flexor,which is same as the peak torque.But the RMS and iEMG of extensor in ankle is smaller than flexor,which is contrary to the peak torque.It shows that standardization of sEMG is necessary for comparing the sEMG of muscle due to a number of interference in surface EMG signal acquisition process.(3)Deep leap process:The sEMG value of lower limbs changes a lot before and after standardization.The standard value of sEMG has the maximum correlation with the jump velocity with the MVIC as standard.So to compare the sEMG of different people with the same muscle or the same person between different muscles with the maximum random contraction as the standard is most reasonable.