The Effect of Weight Support in Muscle Synergies During Upper Arm Movements in Healthy Subjects
Weight support systems are usually used in rehabilitation of upper limbs in neurological patients but the influence of gravity compensation on upper limb muscle activation and in the reorganization of motor control is unclear. Our aim was to study the effect of weight support on muscle activity during upper arm reaching movements in healthy subjects. In particular, we focused on the effect of unloading on muscle synergies, because they seemed to capture muscle activation features, and some aspects of the kinematics and biomechanical request during the execution of motor tasks. We observed that the characteristics of the kinematics of motion varied across weight support conditions but did not show distinct trends with the level of arm weight support. The level of activation of upper limb muscles generally decreased, as expected, with the increase in arm weight support. The same eight muscle synergies were identified in all weight support conditions, and their level of activation depended on the provided level of arm weight support.
This study examined 10 healthy subjects. The protocol included the recording of electromyographic (EMG) activity and hand kinematics of the dominant arm during point-to-point movements between a central location and one of twelve peripheral locations arranged on a circle, either in the sagittal plane or in the frontal plane. These movements were performed with different unloading condition by using the ARMEO Boom system.
This project was done in collaboration with Silvestro Micera at the University of Pisa.