Activity of thigh muscles during static and dynamic stances in stroke patients: a pilot case-control study.

PURPOSE

Impaired postural control is a key characteristic of mobility problems in stroke patients and has great impact on the incidence of falls and on the level of independence in activities of daily living. The role played by the thigh muscles in balance impairment in stroke patients has not been sufficiently investigated. This study investigated the activities of the thigh muscles in stroke patients during standing balance manipulations.

METHOD

Ten stroke patients and 15 healthy subjects performed 5 upright standing tasks on a force platform: normal standing with eyes open, normal standing with eyes closed, feet together, semi-tandem standing, and a dynamic measurement along a predefined route. The posturography parameters, normalized muscle activity by maximal voluntary isometric contraction of the thigh muscles, were measured. The Berg Balance Scale was administered to evaluate functional balance.

RESULTS

The stroke patients showed excessive postural sway compared with healthy control subjects in all conditions of the static balance tests (P < .05). Muscle activity measured by surface electromyography (sEMG) showed higher normalized average EMG (aEMG) in the vastus medialis, rectus femoris, and biceps femoris on the affected side than that in control subjects during all static balance tests (P < .05). The rectus femoris on the unaffected side showed higher aEMG than that in control subjects in the 4 static standing tasks (P < .05). In dynamic tests, the performance time and excursion of the center of pressure were longer in the stroke patients than in the control subjects (P < .05). The activity of the biceps femoris muscle on the affected side was significantly different from that of the control subjects (P < .01).

CONCLUSIONS

The vastus medialis, rectus femoris, and biceps femoris muscles on the affected side and the rectus femoris muscle on the unaffected side of stroke patients are involved in the static balance deficits, while the biceps femoris on the affected side influences dynamic balance control.