Effects of age, temperature, and disease on the refractoriness of human nerve and muscle.

Absolutely and relatively refractory periods have been investigated in terminal median nerve axons and in thenar muscle fibres in a variety of pathophysiological conditions. Marked increased in refractoriness were produced by cooling to 20 degrees C. Nerve fibre refractoriness was more pronounced in older subjects and diminished in myotonic dystrophy. In contrast, no significant changes in muscle fibre excitability could be demonstrated in either condition or in patients with renal failure or motor neuropathies.