Comparison Of The Fatigue Characteristics Of Neck, Shoulder And Waist And Back Muscles In Different Sitting Postures When Using Computer

Objective:The purpose of this study was to compare the changes of s EMG and the flexion angle of the neck,shoulder and back muscles of college students before and after using the computer in different sitting positions,to investigate the characteristics of muscle fatigue in neck,shoulder and back caused by using computer in different sitting positions,and to provide reference for guiding college students to use computer rationally and avoid muscle fatigue.Methods:The subjects were 24 non-sports-major college students who sat in three different postures and watched the video for 60 minutes.The three postures are forward-leaning,upright and backward-leaning sitting postures.The muscles tested were the left and right superior trapezius,the left and right middle trapezius,the left and right Sternocleidomastoid muscle,the left and right latissimus dorsi,the left and right lumbar erector spines。 Before and after the video-watching task,the functional movement screening test,isometric muscle strength test(s EMG signals were collected at same time)were performed respectively.Subjective fatigue assessment and video recording of neck flexion angle were performed during the video-watching task.The integreted electromyography(IEMG),root mean square(RMS),mean amplitude(MA).Frequency-domain indices include mean power frequency(MPF),median frequency(MF)were used to analyze the s EMG.Results:1.The flexibilities of both shoulder joints decreased after forward-leaning sitting(p<0.05),and there was no significant difference in straight lunge squats before and after the three sitting positions(p>0.05).2.The maximal isometric muscle strength of neck,shoulder and back decreased significantly(p<0.01),and the muscle strength of back decreased significantly(p<0.05).3.The subjective muscle fatigue scores of neck and waist were higher after sitting in forward posture than before(p<0.01),and the scores of shoulder and back were higher after sitting in upright posture than before(p<0.05).4.Among the time-domain indices of s EMG,the IEMG and RMS indices after the forward posture test showed an upward trend in the trapezius middle bundle,the trapezius superior bundle,the Sternocleidomastoid muscle,the latissimus dorsi and the lumbar erector spine muscles(p<0.01).The MA index showed an upward trend in the superior trapezius,Sternocleidomastoid muscle,latissimus dorsi and lumbar spine muscles after the experiment(p<0.01).IEMG showed that the superior trapezius,latissimus dorsi and lumbar erector spines showed an upward trend after sitting upright(p<0.01),RMS and Ma showed an upward trend in the superior trapezius,Sternocleidomastoid muscle,latissimus dorsi and lumbar erector spine muscles(p<0.01),while IEMG,RMS and MA showed an upward trend in the superior trapezius bundle after sit-back test(p<0.01).The slope of MPF and MF of the superior trapezius and latissimus dorsi decreased in the frequency domain of surface EMG signal(p<0.05),which indicated that the superior trapezius and latissimus dorsi produced muscle fatigue The slope of MPF of the upper trapezius,latissimus dorsi and lumbar erector spine decreased(p<0.01),resulting in muscle fatigue,while the slope of MPF and MF had no significant difference(p>0.05).5.The flexion angle of the neck in the forward-leaning sitting posture decreased significantly(p<0.01).The angles of forward lean,upright and backward sitting were significantly lower in the last 20 minutes than in the first 20 minutes(p<0.01).The angle of forward-leaning sitting was significantly lower than that of upright sitting(p<0.01)and backward-leaning sitting(p<0.01),and the angle of forward-leaning sitting was significantly lower than that of backward-leaning sitting(p<0.01).The flexion angle of the neck in the forward-leaning sitting posture was significantly greater than that in the upright sitting posture(p<0.05)and the backward sitting posture(p<0.01),and the flexion angle of the neck in the upright sitting posture was also significantly greater than that in the backward sitting posture(p<0.01).Conclusion:1.Long-term use of computers in three different sitting positions can lead to muscle fatigue,such as decreased flexibility of shoulder joint,decreased muscle strength.2.The subjective fatigue of the neck and waist muscles was obvious after sitting forward,and the subjective fatigue of the shoulder and back muscles was obvious after sitting upright.3.The results of surface electromyography showed that the main position of muscle fatigue were neck-shoulder and back after forward leaning sitting,shoulder,back and waist after upright leaning sitting and neck after backward leaning sitting.4.The flexion angle of the neck decreased with time,and the change was most significant during forward leaning sitting,which aggravated the fatigue of the neck muscles.