Effects of an intensive therapy on the precision grip control while walking down a step in children with unilateral cerebral palsy: a self-controlled study.

Grasping with precision depends on predictive and reactive mechanisms. To avoid slips and early fatigue, good coordination between the perpendicular grip force and tangential load forces is required. Grip-load force coordination is affected in children with unilateral cerebral palsy (uCP). This study aimed to assess the effect of Hand-Arm Bimanual Intensive Therapy Including Lower Extremities (HABIT-ILE) on the precision grip of children with uCP while performing a task of walking down a step with a handheld object. Thirty children with uCP (5–17 years old) received 90 hours of conventional therapy followed by 90 hours of HABIT-ILE. To assess the forces coordination before and after each intervention as well as at 4 months of follow up, children walked down a step while holding a grip-lift manipulandum. Dynamic and temporal variables were analysed. The maximum voluntary contraction (MVC) generated during static position, using a precision grip (thumb-index pinch), and the percentage of MVC used for the grip force during the step-down task were also assessed. Just after HABIT-ILE, children presented on the more affected hand a smaller temporal course from minimum load force to maximum load increase. In dynamics, they showed a transitory decrease in load force scaling on the less affected hand. No changes were observed for grip force nor the forces’ ratio on either hand. Children presented an increase of MVC on both hands 4 months after HABIT-ILE, which induced lower percentages of MVC used during the whole task although only significant on the more affected hand. HABIT-ILE can modify transitorily the anticipatory control and the force scaling, as well as the force generation, whose gains are maintained at a long-term. This may explain, at least partially, the functional improvements observed after HABIT-ILE.