Purpose: This study examined the heart rate and dyspnea responses during constant submaximal lower limb endurance exercise in subjects with chronic obstructive pulmonary disease (COPD) to determine the appropriateness of using target heart rate or dyspnea for the prescription of endurance exercise intensity.
Methods: The study participants were 15 men, ages 55 to 75 years, with stable moderate to severe COPD (forced expiratory volume in 1 second, 38.7 +/- 15.6% pred). All the participants completed the incremental shuttle walking test (ISWT) to estimate peak oxygen consumption (VO(2peak)), followed by the endurance shuttle walking test (ESWT) at an intensity equivalent to 60% VO(2peak). Heart rate and dyspnea were monitored before, immediately after, and at 1-minute intervals during each test.
Results: The study was completed by 11 subjects. Heart rate and dyspnea increased significantly between 4.5 and 20 minutes during the ESWT (P <.01) despite walking at a constant submaximal workload. Heart rate and dyspnea attained at the end of the ESWT exceeded levels observed during the ISWT at the equivalent workload (P <.05). Four subjects were unable to walk for at least 10 minutes on the ESWT because of severe dyspnea and were withdrawn.
Conclusions: Setting heart rate and dyspnea targets for endurance training at an intensity equivalent to 60% VO(2peak) may be inappropriate for subjects with moderate to severe COPD because heart rate and dyspnea increase independently of workload at this intensity.