title: [Analysis of the electromyographic characteristics on shoulder fatigue caused by lifting load].
abstract: OBJECTIVE
  To analyze and evaluate the fatigue of shoulder skeletal muscle caused by different lifting loads with surface electromyography (sEMG).
  
  
  METHODS
  According to the loading standard of1 Repetition Maximum (1RM), ten male volunteers performed 3 tasks of upper limb flexion, i.e. 10%, 50% and 90%-1RM. During action process, the signals of Upper Trapezius (UT), Lower Trapezius (LT), Serratus Anterior (SA) and Anterior Deltoid (AD) were recorded by sEMG. The Mean Amplitude (MA) served as an index to evaluate the changes in skeletal muscle fatigue.
  
  
  RESULTS
  The scores of Borg were 15.6, 15.9 and 15.2 for 3 loads of 10%-1RM, 50%-1RM and 90%-1RM, respectively (P > 0.05). The mean amplitudes (MAs) of Upper Trapezius, Lower Trapezius, Anterior Deltoid and Serratus Anterior in shoulders increased obviously. Under the load intensity of 10%-1RM, the MAs of Upper Trapezius and Anterior Deltoid increased significantly (P < 0.05), which were 0.898 and 0.736, respectively. After the exhaustion, the contribution of mean amplitude in shoulder muscle did not change significantly (P > 0.05).
  
  
  CONCLUSIONS
  The low-load action for long time can induce easily the fatigue of upper trapezius and anterior deltoid.
authors.affiliation: Institute of Health and Environmental Medicine, Academy of Military Medical Science, Tianjin, China.
authors.forename: Peng-fei
authors.initials: PF
authors.lastname: Zhao
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ma
authors.forename: Xue-wei
authors.initials: XW
authors.lastname: Chen
authors.forename: Kuan
authors.initials: K
authors.lastname: Zhang
authors.forename: Ting-ting
authors.initials: TT
authors.lastname: Ai
authors.forename: Ze-ming
authors.initials: ZM
authors.lastname: Man
mesh_terms: D000328:Adult; D004576:Electromyography; D006801:Humans; D017770:Lifting; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D012782:Shoulder / Q000502:physiology*; D016526:Workload