Discrepancy between functional exercise capacity and daily physical activity: a cross-sectional study in patients with mild to moderate COPD

Background: In patients with moderate to severe chronic obstructive pulmonary disease (COPD) the six-minute walk distance reflects the functional exercise level for daily physical activity. It is unknown if this also applies to patients with mild to moderate COPD in primary care. Aims: To assess the relationship between functional exercise capacity and physical activity in patients with mild to moderate COPD. Methods: A cross-sectional study was performed in 51 patients with mild to moderate COPD in primary care. Functional exercise capacity was assessed by the six-minute walk test and physical activity was measured with an accelerometer-based activity monitor. Results: Functional exercise capacity was close to normal values. However, the daily physical activity of the patients could be classified as 'sedentary' and 'low active'. No significant correlations were observed between six-minute walk distance (% predicted) and any of the physical activity variables (steps per day, movement intensity during walking, total active time, total walking time, physical activity level, and time spent in moderate physical activity). Conclusions: A discrepancy was found between functional exercise capacity and daily physical activity in patients with mild to moderate COPD recruited and assessed in primary care. We conclude that these variables represent two different concepts. Our results reinforce the importance of measuring daily physical activity in order to fine-tune treatment (i.e. focusing on enhancement of exercise capacity or behavioural change, or both).