[Analysis of surface electromyography on repetitive lifting task-induced fatigue of back muscles].
OBJECTIVE
Using surface electromyography (SEMG) technique to evaluate repetitive lifting task-induced fatigue of back muscles.


METHODS
Thirteen volunteers lifted and lowered an 8 kg weight from floor to waist level for 100 times. Fatigue in the erector spinae muscles was quantified by comparing the frequency content of the EMG signal during static contractions performed before, and immediately after the 100 lifts.


RESULTS
EMG average amplitude rose gradually during 100 lifts, the difference was significant at T10 right (P < 0.05) and L3 left (P < 0.01), the difference was not significant at T10 left and L3 right (P > 0.05). The median frequency intercept at T10 right, T10 left, L3 right, L3 left erector spinae muscles decreased by 2.0% (P > 0.05) 10.9% and 29.9% (P < 0.05), 27.9% (P < 0.01), respectively. The mean power frequency intercept decreased by 9% at L3 left erector spinae muscle (P < 0.05), the decrease was not statistically significant at other sites (P > 0.05).


CONCLUSIONS
Repetitive lifting may induce measurable fatigue in the erector spinae muscles. Erector spinae muscle at L3 is more easily fatigued than at T10. Using the median frequency intercept to assess muscle fatigue is more sensitive than using mean power frequency intercept.
Chen
Jing
J
School of Public health, Tongji Medical College, Huazhong Science and Technology University, Wuhan 430030, China.
Ding
Jia-Shun
JS
Wang
Zheng-Lun
ZL
Yang
Lei
L
D000328:Adult; D001415:Back; D004576:Electromyography; D006801:Humans; D017770:Lifting; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*