Lower limb activity and its determinants in COPD.

ABSTRACT

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) walk less than healthy older people and their self-reported activity predicts exacerbation risk. The relationship between lower limb activity and total daily activity is not known, nor are there any data which relate objectively assessed daily activity to laboratory assessments made before and after rehabilitation. METHODS: Lower limb activity was measured by leg actigraphy over 3 days in 45 patients with moderate to severe COPD and 18 controls of similar age. Thirty-three patients with COPD entered an 8-week rehabilitation programme in which the change in leg activity was measured and related to other outcomes. RESULTS: In patients with COPD the mean level of activity measured by whole body and leg activity monitors was closely related (r = 0.92; p<0.001), but leg activity was consistently reduced compared with controls of similar age (p = 0.001). Mean leg activity, mean intensity of leg activity and the time that patients spent mobile at home were all related to forced expiratory volume in 1 s (FEV(1)) (r = 0.57, p = 0.001; r = 0.5, p = 0.003; and r = 0.51, p = 0.002, respectively), but intensity of activity and time spent mobile were not related. Subjects completing pulmonary rehabilitation showed significant improvements in mean activity (p = 0.001) and spent more time moving (p = 0.014). These changes were unrelated to improvement in muscle strength or walking distance but correlated with baseline FEV(1) (r = 0.8, p<0.001). CONCLUSIONS: Total daily activity in patients with COPD is closely related to leg activity which is reduced compared with controls of similar age. Individuals differ in the time spent mobile during the day, but subjective and objectively assessed activity improves after rehabilitation and is predicted by FEV(1). The change in activity is unrelated to improvements in corridor walking and health status.