Temperature dependence of the electrical and mechanical responses of the adductor pollicis muscle in humans.

Changes at low temperatures of the electrical and mechanical activity of the adductor pollicis muscle were studied in 10 volunteers. Decreasing temperatures resulted in increased amplitude and duration of the negative phase and peak-to-peak amplitude of the evoked muscle action potential. Distal latency, electromechanical latency, contraction time, and half-relaxation time were also increased while isometric force, contraction velocity, and relaxation velocity were decreased. The increase of contraction time is greater over the temperature range below 28 degrees C than above 29 degrees C. Skin temperature differs significantly from muscle temperature, showing about 3 degrees C lower values during cooling and up to 4 degrees C higher values during rewarming with radiant heat.