Measurement of synergy and spasticity during functional movement of the post-stoke hemiplegic upper limb

The aim of the present study was to measure the muscle-contraction patterns of the hemiplegic upper limb using electromyography (EMG) and to investigate the relationship between muscle co-contraction and functional recovery in stroke patients presenting with synergy and spasticity. The muscle-contraction patterns of the upper limb of 12 chronic stroke patients and 10 normal volunteers were measured, and the co-contraction in the distal and proximal muscles was simultaneously quantified, while the participants performed hand-grasp and shoulder flexion tasks. The spasticity and hemiplegic arm function were evaluated, respectively, on a modified Ashworth scale (MAS) and by means of Fugl-Meyer motor assessment (FMA). The correlation between the MAS and FMA values was analyzed.Increased co-contraction (66–555%) was observed in both the proximal and distal upper limbs, and was positively correlated with spasticity of the elbow flexor (r = 0.944 on shoulder flexion, r = 0.741 on hand grasping, p < 0.01) and negatively correlated with functional recovery of the upper limb (r = ?0.670 ～ ?0.884, p < 0.05). Specific movement patterns influenced by synergy and spasticity were confirmed by EMG. These results might prove useful to the formulation of appropriate management plans such as those involving botulinum toxin injection or nerve block.