Focal Muscle Vibration Combined with Electrical Stimulation for Post-Stroke Upper Limb Spasticity: A Pilot Study

Post-stroke upper limb spasticity is a common condition characterized by increased muscle tone which interferes with rehabilitation, limits functional activities, and imposes a significant burden on patients and caregivers. Current treatments, including medications, injections, and physical therapy, often have limited effectiveness or produce side effects. Although some evidence supports focal muscle vibration (FMV) and electrical stimulation individually to reduce spasticity, the benefit of combining these modalities remains unclear. This pilot study explored the immediate effects of combining FMV with electrical stimulation on finger flexor spasticity in stroke survivors, aiming to identify combinations of FMV, neuromuscular electrical stimulation (NMES), and transcutaneous electrical nerve stimulation (TENS) that produce immediate reductions in hypertonia. Five stroke survivors were evaluated in repeated trials (804 trials in total) under 48 different conditions involving FMV (percussive and non-percussive), NMES (35 Hz and 100 Hz), and TENS, applied either alone or in combination to the spastic or antagonist muscles of the forearm. Interventions were applied for 10 s, and the Modified Ashworth Scale (MAS) score was assessed immediately before and after each stimulus. In a multinomial model adjusted for participant, percussive FMV with NMES, particularly at 100 Hz, yielded the greatest immediate reductions in MAS scores, with a higher likelihood of reducing MAS to 0 or 1 than percussive FMV alone; for the 100 Hz combination, this was observed in each of the five participants. In contrast, non-percussive FMV and TENS alone showed limited effectiveness, with a higher probability of no change. These preliminary findings indicate that combining percussive FMV with NMES can produce an immediate reduction in finger flexor hypertonia under the tested conditions. Confirmation in larger, blinded studies with longer stimulation and follow-up periods is needed to establish efficacy.