Functional effect of short-term immobilization: kinematic changes and recovery on reaching-to-grasp

Although previous investigations agree in showing significant cortical modifications related to short-term limb immobilization, little is known about the functional changes induced by non-use. To address this issue, we studied the kinematic effect of 10h of hand immobilization. In order to prevent any movement, right handed healthy participants wore on their dominant hand a soft bandage. They were requested to perform the same reaching-to-grasping task immediately after immobilization, 1 day before (baseline 1) and in other two following days without non-use (baseline 2 and baseline 3). While no differences were found among baseline conditions, an increase of the total duration of reaching movement together with an anticipation of the time to peak velocity were observed in the first trial after immobilization. Interestingly, these initial effects decreased quickly trial-by-trial, following an exponential function till reaching values equal to those observed in the control conditions. The present findings show firstly that the transport phase of the reaching-to-grasp task was affected by a temporary reduction of sensory and motor information. Secondly, a trial-by-trial recovery of the immobilization-related changes, likely driven by the sensory inputs and motor outputs associated to the repetition of the movement has been observed. All together these results confirm a fundamental role of a continuous stream of sensorimotor signals in maintaining motor efficiency and in driving recovery process.