THE MATURATION OF MOTOR DEXTERITY - OR WHY JOHNNY CANT GO ANY FASTER

The speed of alternating movements at the ankle, healthy children and 13 adults doubled between age 3 and 11 years, despite a 32-fold increa se in limb-segment inertia produced by the doubling in limb length ove r the same period. The data for the children showed little or no pract ice effect. The speeds for the adults, though faster than those for th e children, were more widely dispersed, indicating the possibility tha t training might increase the speed of the slowest adult. The findings are consistent with a previous report demonstrating a parallel increa se in the speed of calf muscles over the first 10 years of life and it is inferred that the increase in dexterity at the wrist and metacarpo phalangeal joints also depends on an increase in muscle speed with age . Muscle maturation may impose a rate-limiting envelope for all motor tasks which is particularly evident in rapidly alternating movements. These findings have implications for training in sport and music and f or the understanding of motor delay, clumsiness and speech difficultie s.