Segmental muscle vibration modifies muscle activation during reaching in chronic stroke: A pilot study

BACKGROUND: Segmental muscle vibration (SMV) improves motor performances in neurological conditions, including stroke. OBJECTIVE: To determine if SMV modifies upper limb muscular activity in chronic stroke patients performing a reaching movement. METHODS: We randomized 22 chronic stroke patients to an experimental group (EG; n = 12), receiving 10 sessions of exercise + 120 Hz SMV over the biceps brachii (BB) and the flexor carpi ulnaris (FCU) muscles, or to a control group (CG; n = 10) receiving exercise only. All subjects performed a reaching movement with the affected side before and 4 weeks after therapy ended. We recorded surface EMG activity of the anterior deltoid (AD), posterior deltoid (PD), BB, triceps brachii (TB), FCU and extensor carpi radialis (ECR) muscles. We calculated muscular onset times, modulation ratio, co-contractions and degree of contraction. RESULTS: After SMV, onset times of the PD (p = 0.03), BB (p = 0.02) and ECR (p = 0.04) in the EG were less anticipated than at baseline; the modulation ratio increased in AD (p = 0.003) and BB (p = 0.01); co-contractions decreased in the pairs BB/TB (p = 0.007), PD/BB (p = 0.004) and AD/BB (p = 0.01); and the degree of contraction decreased in BB (p = 0.01). CONCLUSIONS: The modulation of muscular function induced by SMV may aid to explain its action on smoothness and coordination of movements.