Background: Patients with 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 is there data relating objectively assessed daily activity to laboratory assessments made before and after rehabilitation.
Methods: We measured lower limb activity by leg actigraphy over 3 days in 45 patients with moderate to severe COPD and 18 similar age controls. Thirty-three COPD patients entered an 8-week rehabilitation programme where we measured the change in leg activity and related this to other outcomes.
Results: In COPD patients mean activity level 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 similar age controls (p=0.001). Mean leg activity, mean intensity of leg activity and the time that patients spent mobile at home were all related to FEV1 (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 FEV1 (r=0.8; p<0.001).
Conclusions: Total daily activity in COPD patients is closely related to leg activity which is reduced compared to similar age controls. Individuals differ in the time spent mobile during the day but both subjective and objectively assessed activity improves after rehabilitation and is predicted by FEV1. The change in activity is unrelated to improvements in corridor walking and health status.