Multifinger ab- and adduction strength and coordination.

Simultaneous abduction and adduction of the fingers (finger spreading and finger squeezing) are fundamental to many prehension tasks. This is the first study to describe all finger forces during multifinger ab-/adduction. Twenty-one healthy subjects (12 female) produced maximal ab-/adduction (AbAd) efforts against a stationary apparatus equipped with four independent multiaxis force transducers. Total force was computed as the sum of the absolute values of individual finger forces. The males were significantly stronger than the females, and adduction (squeezing) forces (42.4N) were significantly greater than abduction forces (32.6N). The relative contributions of individual fingers to the total force were consistent across the genders, implying that strength did not affect coordination. AbAd were coordinated symmetrically and multifinger performance was not predictable from single-finger strengths. The latter finding, in particular, indicates that multifinger spreading/squeezing force measurements can provide information about hand function that cannot be derived from other tests.