A key limitation of the study is that physiological variables were unknown prior to admission. For example, the 17% increase in QMVC observed in the PEPR group may represent recovered muscle strength lost during admission or improvement above baseline. Healthy subjects lose 16% of isokinetic muscle strength during 10 days of bed rest,38 while patients with COPD have been reported to lose 5% of their predicted quadriceps force during an exacerbation.12 Inactivity is prominent during exacerbations and contributes to the development of weakness. In the present study, subsequent exacerbations requiring emergency department attendance or admission were associated with a reduction in quadriceps strength and would support a model whereby recurrent exacerbations lead to a downward functional spiral and loss of physiological reserve. This assertion is supported by accelerometry studies reporting reduced weight-bearing activity 1 month after an exacerbation, and an association of such activity with quadriceps strength.11 Accelerometry was not performed in this study to assess whether change in daily activity related to change in exercise capacity or quadriceps strength.