【Objective】To investigate the important factors for exercise capacity in patients with stable chronic obstructive pulmonary disease (COPD). 【Methods】A total of 109 consecutive subjects with stable COPD underwent a six-minute walk test (6MWT)

while inspiratory capacity (IC) was recorded before and immediately after walking. Spirometry

quadriceps muscle function

the Modified Medical Research Council (mMRC) dyspnea scale

St George’s Respiratory Questionnaire (SGRQ)

Pittsburgh Sleep Quality Index (PSQI)

Epworth Sleeping Scale (ESS)

Hamilton Anxiety Scale (HAMA) and Hamilton Depression Scale (HAMD) were also assessed. 【Results】Multiple stepwise regression analysis was performed to identify that the significant predictors of six-minute walk distance (6MWD) were age (standardized coefficient β=-0.264

P =0.007)

HAMD score (β=-0.246

P =0.005)

SGRQ activity score (β=-0.194

P =0.029) and strength in quadriceps muscle (β=0.197

P =0.030). 【Conclusion】Age

depression

physical activity in daily life and strength in quadriceps muscle may be the major factors associated with functional exercise capacity in patients with stable COPD