Stroke patients have selective muscle weakness in shortened range

Weakness is recognized as a major problem after stroke. This study examined the torque-angle curves of stroke individuals and compared them with those of neurologically normal controls to determine (i) if stroke patients were selectively weak when their muscles were placed in a shortened range and (ii) whether contracture influenced any selective weakness. This descriptive research study measured elbow flexor and extensor torque-angle curves and contracture. Twenty-two stroke subjects who had suffered a stroke 5 months to 6 years ago and 11 neurologically normal controls of similar age participated. Torque-angle curves of the elbow flexors and extensors were determined by measuring maximum isometric torque at 0, 20, 40, 60, 80, 100 and 120degrees of elbow flexion (0degrees being full elbow extension), where possible. Contracture of the elbow flexors and extensors was measured as the loss of passive elbow joint range of motion. Repeated measures analysis of variance revealed that the torque-angle curves of stroke subjects (with or without contracture) were significantly different from those of the control subjects for both the elbow flexors (P < 0.05) and extensors (P < 0.05). The stroke subjects appeared relatively weaker when the muscles were in their shortened range. This study confirms that selective weakness exists at short muscle lengths after stroke. The findings of this study help to explain why people after stroke have difficulty functioning when their muscles are in their shortened range. Therefore, strength training should be targeted specifically at muscles at their shortened lengths in order to promote the recovery of function after stroke.