Effects Of Different Interventions On Activation Patterns Of Trapezius Muscle

Objective: Trapezius muscle is not only important for maintaining good posture,but also plays an important role in sports,exercises and competitions.The correct patterns of muscle activation is the foundation of scapula's normal position,and prevention and recovery from shoulder impingement syndrome,shoulder joint disorders and neck pain.This article provides a theoretical basis for the study of the activation pattern of trapezius muscle through electromyography.Methods: In this study,subjects included 20 normal people and 20 mild discomforts in the shoulder joint.All subjects underwent no intervention,static stretching of the upper trapezius(UT),isometric contraction of the lower trapezius(LT),and static traction of UT combined with isometric contraction of LT.The testing actions included straight-arm lateral raise,seated row,and reverse fly.Before and after the test,the EMG signal was recorded and the pain was assessed.Results:(1)In the normal people: During seated row action,the extent of trapezius recruitment was LT>MT(middle trapezius)>UT,the activation time sequence was MT,LT and UT.During reverse fly action,the extent of trapezius recruitment was MT>LT>UT,the activation time sequence was LT,MT and UT.During straight-arm lateral raise action,the extent of trapezius recruitment was UT>LT>MT,the activation time sequence was MT,UT and LT.Compared with the normal people,there were an increased level and early activation of UT,decreased levels and delayed activations of MT and LT,and increased ratio of UT/MT and UT/LT in subjects who had mild shoulder discomforts.(2)The intervention of the static stretching of UT had positive effects on the regaining of the correct activation patterns in subjects who had mild shoulder discomforts,demonstrating decreased level and delayed activation time of UT,decreased ratio of UT/MT and the pain(p<0.05).(3)The method of isometric contraction of LT had positive effects on the regaining of the correct activation patterns in the subjects who had mild shoulder discomforts,demonstrating increased level and early activation time of UT,and decreased ratio of UT/MT,UT/LT and the pain(p <0.05).Conclusions:(1)The activation time and level were different in three digitations of trapezius muscle during different movements.In the normal mode,LT got the biggest extent of activation in seated row movement,and earliest activation in reverse fly movement.(2)The intervention of isometric contraction of LT could effectively increase the extent of participation of LT and promote early activation of LT during movement.(3)The intervention of static stretching of UT could effectively reduce the extent of activation of UT,delay activation of UT,and correct the abnormal activation of UT.(4)People with mild shoulder discomforts may return to normal activation pattern after intervention of isometric contraction of LT,which suggested that interventions should be made as early as possible if any symptoms were found during exercise.