Effect of Gravity Compensation on Upper Limb Muscle Synergies during Reaching: Preliminary Results from Healthy Subjects

Support against gravity is a promising strategy to enable upper extremity rehabilitation in neurological patients. While such support facilitates reaching in subjects with severe impairments, its effect on the reorganization of muscle activations has not been investigated. In particular, it remains unclear what amount of weight compensation should be employed to achieve maximal functional recovery. To provide insights into these issues, we studied muscle synergies during the execution of 3D reaching movements under six different levels of arm-weight support. Our preliminary results suggest that gravity compensation decreases the level of muscle synergy activations required for task performance. However, whether weight support could induce changes in the muscle-synergy structures awaits further confirmation.