Finger force sharing during an adapted power grip task.

This study analyses the finger force sharing using power grip task with adapted experimental conditions. This paradigm limits as much as possible the external constraints when the Index (I), Middle (M), Ring (R) and Little (L) fingers act simultaneously: the thumb did not oppose the other fingers and no secondary moments were applied to the wrist. The motor control of these two parameters was limited in contrary to the previous paradigms of the literature. The results showed that the force sharing, the force deficit and the location of the neutral line were different in this condition compared to a classical finger pressing task. We suggest that the observed behaviour was due to the peripheral architecture (muscle bellies, multi-digit motor units) more than the control of the constraints of the tasks. We propose to use this paradigm in further fundamental studies and also during clinical programmes to evaluate the rehabilitation of peripheral architecture characteristics and also finger control.