Effects of temperature on electromyogram and muscle function

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Abstract
The effects of 30 min of cooling (15°C water) and warming (40°C water) on arm muscle function were measured. A reference condition (24°C air) was included. Of nine young male subjects the maximal grip force (F max), the time to reach 66% ofF max (rate of force buildup) and the maximal rhythmic grip frequency were determined, together with surface electromyographic activity (EMG) of a forearm muscle (flexor digitorum superficialis). The results showed that in contrast to warming, cooling resulted in a significant decrease of 20% in the FmaX and a significant 50% decrease in force build-up time and the maximal rhythmic grip frequency. The relationship between the root mean square value (rms) of the EMG and the static grip force did not change due to temperature changes. The median power frequency (MPF) in the power spectrum of the EMG signal decreased by 50% due to cooling but remained unchanged with heating. During a sustained contraction at 15% ofF max (F max depending on the temperature) the increase in the rms value with contraction time was 90% larger in the warm condition and 80016 smaller in the cold condition compared to the increase in the reference condition. The MPF value remained constant during the warm and reference conditions but in the cold it started at a 50% lower value and increased with contraction time. Since the endurance time was not affected in the cold but 60% reduced in the warm, it was concluded that neither the rms nor the MPF reflected unambiguously the temperature related changes in functional performance of muscle strain with an equal relative load.

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