Inherent bimanual postural synergies in hands.

This paper presents a numerical approach to prove the existence of inherent bimanual postural synergies while performing actions with two hands. Five subjects were tested in two different tasks. The first task was a well coordinated task where each subject screwed nut and bolt using one or both hands. In the second task, subjects were asked to perform several random postures with both hands. Joint angles were measured during the experiment by a pair of data gloves. Principal component analysis (PCA) was performed over the postures obtained during the tasks. In the first task, the number of postural synergies obtained for both hands together was less than the sum of the number of postural synergies for two hands. This is expected intuitively as first task was well coordinated. In the second task where there is no voluntary coordination involved, the number of postural synergies obtained for both hands together was still less than the sum of the number of postural synergies for two hands. This implies that there are innate bimanual synergies wired biomechanically to help brain in bimanual movements.