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.