Influence of posture and muscle length on stretch reflex activity in poststroke patients with spasticity

Objective: To investigate the influence of different positions on stretch reflex activity of knee flexors and extensors measured by electromyography in poststroke patients with spasticity and its expression in the Ashworth Scale. Design: Crossover trial with randomized order of positioning. Setting: Outpatient rehabilitation center in the Netherlands. Participants: Poststroke patients (N=19) with lower-limb spasticity. Intervention: Changing position: sitting versus supine. Main Outcome Measures: Root mean square (RMS) values of muscle activity and goniometric parameters, obtained during the pendulum test and passive knee flexion and extension, and Ashworth scores. Results: RMS values of bursts of rectus femoris activity were significantly higher in the supine compared with the sitting position (P=.006). The first burst of vastus lateralis activity during, the pendulum test (P=.049) and semitendinous activity during passive stretch (P=.017) were both significantly higher in the supine versus the sitting position. For both the pendulum test and passive movement test, the duration and amplitude of the cyclic movement of the lower leg changed significantly as well. In the supine position, we found significantly higher Ashworth scores for the extensors (P=.001) and lower scores for the flexors (P=.002). Conclusions: The outcome of clinical and neurophysiologic assessment of spasticity is influenced considerably by subject positioning.