RATIONALE: We hypothesized that among patients with chronic obstructive pulmonary disease, those who develop quadriceps contractile fatigue (QCF) after exhaustive submaximal cycle exercise would have a greater response to exercise training than those who do not develop QCF (NQCF).
METHODS: Patients (N = 132) had measurement of QCF at baseline. Six-minute walk distance (6MWD), maximal incremental cycle exercise testing, and quality of life measured by the Chronic Respiratory Questionnaire were obtained before and after pulmonary rehabilitation (PR).
RESULTS: Eighty of the 132 patients (60.6%) developed QCF following constant workload exhaustive cycle exercise. Patients who developed QCF had a significantly greater improvement in 6MWD following PR (45.3 ± 45.2 m) than those who did not (27.5 ± 45.7 m; P= .032). When baseline differences between patients who developed QCF and NQCF were accounted for, the difference in 6MWD remained significant. Patients who developed QCF were not more likely to identify leg fatigue as the factor limiting exercise (56.2% of QCF group stated that leg fatigue was the limiting factor compared with 47.9% in the NQCF group; P= .46). When baseline differences were accounted for, the symptom causing exercise termination was not a predictor of the response to PR.
CONCLUSION: Patients who were capable of developing QCF had a significantly greater improvement in 6MWD after PR compared to NQCF. Symptoms causing exercise termination could not be used to predict the development of contractile fatigue or the response to PR.