Physical activity in patients with chronic obstructive pulmonary disease.

Exercise capacity and physical activity (PA) is low in patients with chronic obstructive pulmonary disease (COPD). PA has been shown to impact upon hospitalisation and is one of the best predictors of all-cause mortality in patients with COPD (Waschki et al., 2011, Chest, 140(2), 331–342). However, there is limited data on PA in relation to the American College of Sports Medicine (ACSM) guidelines with most authors reporting PA as total time above 3 metabolic equivalents (METs) and not in bouts of at least 10 consecutive minutes. Completing PA in bouts of consecutive minutes of at least 10 min rather than totalling individual minutes of non-bouts activity is important to ensure health benefits are gained. The aim of this study was to describe the PA levels of patients with COPD in accordance with disease severity and to examine the impact of using non-bouts and bouts of PA in determining if the ACSM guidelines have been met. With National Research Ethics Service (NRES) ethical approval, 154 patients with COPD (mean (s): age 68 (8) years; BMI 27 (6) m · kg−2; FEV1% predicted 49 (18)%) were consented as part of a larger randomised controlled trial. Patients were categorised according to Medical Research Council (MRC) dyspnoea scale, with grade 5 being the most severe. Patients were instructed to wear a SenseWear Pro 2 armband for all waking hours on 5 standardised days. Outcome measures were step count and time above 3 METs. Mean (s) daily step count was 3919 (2624) steps. There was a statistically significant difference between step count and MRC dyspnoea grade. Those in MRC grade 5 (2382 (2046) steps) had significantly less steps than MRC dyspnoea grades 2 (5824 (3027) steps, P ≤ 0.01), 3 (3908 (2162) steps, P ≤ 0.01) and 4 (3278 (2351) steps, P ≤ 0.01). Mean (s) daily time over 3 METs was 58 (48) min (67% meeting guidelines), which reduced to 15 (22) min (18% meeting guidelines) once data in at least 10 consecutive minute bouts were analysed (P ≤ 0.01). Patients with COPD are inactive. Levels of PA decline with increasing MRC grade and are lowest in those with higher levels of dyspnoea. There is a significant reduction in time in PA and the number of patients meeting the ACSM guidelines when using the 10-min bout data in comparison with non-bout data. How PA is reported can affect the interpretation and if not reported in bouts of at least 10 min may mask the need for PA intervention.