Difference in dynamic motor function of individual fingers and effects of long-term training.

The purposes of this study were to assess differences among the index, middle, ring, and little fingers in dynamic motor function, using single-finger-tapping and double-finger-tapping tasks, and to investigate the effect of long-term training on dynamic motor function, using trained pianists. Four miniature strain gauge force transducers were used to measure the external force generated by each finger during tapping. Twelve healthy male adults and three female adult pianists tapped force transducers for 9 seconds as fast as possible, using their dominant right hands, while the other fingers contacted with the force transducers. In the single-finger tapping, we asked subjects to tap using each finger: index, middle, ring, and little finger. In the double-finger tapping, subjects performed alternating movements of a pair of fingers. A comparison among the four fingers in single-finger tapping revealed that the index and middle fingers attained significantly faster tapping, indicating the superiority of these two fingers over the other two fingers in terms of dynamic motor function. Changes in isometric forces generated by the non-tapping fingers accompanied the tapping finger movements; the correlation between tapping and non-tapping fingers was greater for the ring finger than for the other fingers. This suggests that the ring finger is more dependent on the movements of other fingers, especially neighboring fingers. Differences among the fingers in dynamic motor function could result from anatomical and neurophysiological factors. During two-finger movement, the dynamic motor function of each finger was affected by the combination of fingers. Finger combinations that are less used in ordinary life had lower tapping speeds than the other combinations. For pianists, tapping rates of the little and ring fingers in single-finger tapping were similar to those of the index and middle fingers. There was less accompanying force by non-tapping fingers of the pianists than of non-pianists. In double-finger tapping, tapping rates for any combination of fingers was nearly the same for the pianists. These suggested that long-term training could alter dynamic motor function of the fingers.