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Physiological studies have been made of extensor digitorum brevis muscles in 28 healthy subjects aged between 60 and 96. Within this elderly population there was evidence of muscle wasting and weakness. These changes were shown to result from a loss of functioning motor units. The surviving motor units were often enlarged and tended to have relatively slow twitches. In some subjects the maximum impulse conduction velocities were reduced in motor nerves; there was evidence that slowing of impulse conduction could be especially marked in distal regions of axons. The findings are considered to indicate the presence of motoneurone dysfunction in old age. [ABSTRACT FROM AUTHOR]

Isometric twitch contractions have been studied in extensor hallucis brevis muscles of 32 healthy male subjects aged between 3 and 25 years. The maximum twitch tensions were found to increase gradually with age and then to undergo marked enhancement at puberty. After puberty little further change occurred. In the youngest children examined the twitch contraction times were already within the adult range, though the half-relaxation times were prolonged. [ABSTRACT FROM AUTHOR]