Association of activity limitations and lower-limb explosive extensor power in ambulatory people with stroke.

OBJECTIVE To determine whether the explosive lower-limb extensor power of the affected and unaffected sides, and any asymmetry, are associated with activity limitations after stroke. DESIGN Cross-sectional observational study of baseline data from a randomized controlled trial. SETTING Measurements made in a hospital clinical research facility. PARTICIPANTS Community-dwelling (N=66) subjects with stroke who were independently ambulatory. Subjects' mean age was 72+/-10 years. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES The lower-limb extensor power of each lower limb (in W/kg), performance of specific functional activities (comfortable walking velocity, Functional Reach Test, chair-rise time, Timed Up & Go test), and global indices of activity limitation (FIM instrument, Rivermead Mobility Index, Nottingham Extended Activities of Daily Living). RESULTS Low lower-limb extensor power in either lower limb was the principal factor from among the confounders we recorded that significantly (R(2) range, .21-.46) predicted the limitation of specific functional activities, and low lower-limb extensor power in either lower limb was the principal predictive factor for global indices of activity limitation (R(2) range, .13-.38). The degree of asymmetry of lower-limb extensor power between legs was low and had little or no predictive value. CONCLUSIONS In ambulatory persons with stroke, activity limitations are associated with deficits in lower-limb extensor power of both lower limbs, and not the severity of any residual asymmetry. These findings suggest that interventions to increase lower-limb extensor power in both lower limbs might reduce activity limitations after stroke.