MAXIMUM CONDUCTION VELOCITIES OF MOTOR FIBERS OF ULNAR NERVE IN HUMAN SUBJECTS OF VARIOUS AGES AND SIZES

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Abstract
By means of recorded muscle action potentials elicited in response to percutaneous electrical stimulation of the ulnar nerve at 2 or 3 points on the arm, conduction velocity measurements of the most rapidly conducting ulnar nerve fibers supplying the muscles of the hypothenar eminence were made on human subjects whose ages ranged from 3.5-82 yrs. The max. conduction velocity of these nerve fibers which is found in young adults may be attained as early as the 4th-5th yrs. of life. Therefore, from so early an age, the time consumed by the motor impulse in travelling from the spinal cord to the periphery increases as the individual grows, and is less in small than in large individuals of the same age. Similar considerations probably hold true for total reflex time. Beyond an advanced age (60 yrs. in these studies) conduction velocity decreases with a consequent probable lengthening of reflex time. Possible explanations for this slowing are: (1) selective degeneration of the largest nerve fibers supplying the muscles of the hypothenar eminence; (2) lowered O2 supply and consequent lowered metabolism of the nerve cells; (3) lowered temp. of the nerves along with other deep tissues of the forearm.