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.