Significance of skin temperature changes in surface electromyography |
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Authors: | J Winkel K Jørgensen |
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Institution: | (1) National Institute of Occupational Health, Department of Physiology, Division of Applied Work Physiology, S-17184 Solna, Sweden;(2) August Krogh Institute, University of Copenhagen, Copenhagen, Denmark |
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Abstract: | Summary Differing results have been reported concerning the direction and quantity of the electromyogram (EMG) amplitude response to changes in tissue temperature. The EMG signals from the soleus muscle of six healthy human subjects were therefore recorded during dynamic exercise (concentric contractions) at ambient temperatures of 30°C and 14°C. The mean skin temperature
above the muscle investigated was 32.9° C and 21.7° C, respectively. The core temperature, estimated by rectal temperature, was unchanged. The cooling of the superficial tissues caused approximately a doubling of the EMG amplitude. For the probability level 0.9 in the amplitude probability distribution function, the average signal level increased from 73 V to 135 V (P=0.02). The average mean power frequency of the EMG signal was reduced from 142 Hz to 83 Hz (P=0.004). The amplitude increase was not due to shivering but other possible explanations are presented. As the changes in T
sk investigated were within the range which may occur normally during the working hours, it was concluded that T
sk should be carefully controlled in vocational EMG studies. |
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Keywords: | Electromyogram amplitude Mean power frequency Dynamic exercise Temperature Soleus muscle |
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