Original article
Influence of Posture and Muscle Length on Stretch Reflex Activity in Poststroke Patients With Spasticity

Presented in part to the Spasticity Conference on December 10, 2004, Newcastle upon Tyne, United Kingdom.
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Abstract

Fleuren JF, Nederhand MJ, Hermens HJ. 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.

Section snippets

Methods

This explorative study was a crossover randomized trial in which the order of positioning was randomized for all patients. Randomization was performed mainly because of the occurrence of fatigue in repeated stretching of a spastic muscle.26, 27

The study received ethics approval from the medical ethics committee of Rehabilitation Centre Het Roessingh in Enschede, the Netherlands.

Results

Twenty patients were recruited from the outpatient Department of Rehabilitation Medicine. All patients were informed about the purpose of the study and gave informed consent. The results of 1 subject in group A were excluded for further analysis, because the subject appeared unable to relax during all the measurements.

Table 1 summarizes the baseline characteristics of groups A and B. The difference in mean age between the 2 groups was significant (Mann-Whitney U test, P=.04).

Discussion

The aim of this study was to investigate the influence of position on stretch reflex activity of knee flexor and extensor muscles in stroke subjects with known spasticity in the affected leg. In addition to what was done in earlier studies,18, 19, 20 we performed the Ashworth Scale in 2 positions and recorded surface electromyography during the pendulum test and passive movement of the limb.

The results of the neurophysiologic tests in this study confirm our hypothesis that a muscle in an

Conclusions

Clinical and neurophysiologic assessment of spasticity is influenced considerably by change in posture and muscle length. For comparable assessment of spasticity exact documentation of patients’ positions is essential. We strongly support the recommendation to standardize testing protocols.7, 8

Acknowledgments

We thank Anand Nene for his comments on this manuscript and Karin Groothuis-Oudshoorn for her help with statistical analysis. We also thank Leendert Schaake and Victorien Erren-Wolters for their assistance during the measurements.

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