Effects of Tendon Pressure on Alpha Motoneuron Excitability in Patients with Stroke

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Abstract
The purpose of this study was to evaluate the effects of two intensities (5 and 10 kg) of continuous and intermittent Achilles tendon pressure on the H-reflex in eight hemiparetic subjects. A decrease in the H-reflex was interpreted as a depression in motoneuron excitability, a condition conducive for reducing muscle tone. The H-reflex measurements were obtained before, during, immediately after, and 2.5 minutes after tendon pressure application. Piecewise linear regression equations were used to evaluate the effects of four pressure conditions. The mean of the midpoints of the lines for each pressure condition was compared with prepressure baseline values by t tests and with the other pressure conditions by an analysis of variance. All four pressure conditions demonstrated H-reflexes less than prepressure baseline values, with three of the four conditions (5 and 10 kg of intermittent pressure and 5 kg of continuous pressure) being significantly less than prepressure baseline values (p < .05). The analysis of variance revealed a significant difference among pressure conditions. Scheffé post hoc contrast comparisons revealed significant differences between intermittent and continuous pressure but not between 5 and 10 kg of pressure. The results of this study indicate that in these hemiparetic subjects, the H-reflex was depressed during both continuous and intermittent tendon pressure. Intermittent pressure was more effective then continuous, but 10 kg of pressure had no greater effect than 5 kg of pressure. The effects of pressure lasted only as long as the stimulus was present. Therapeutic techniques that might take advantage of this decrease in motoneuron excitability include stretching of shortened musculotendinous units, strengthening of antagonists, and improving lower extremity bed and wheelchair positioning.

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