Key result
Exercise limitation in COPD is primarily driven by inadequate energy supply and impaired oxygen delivery to locomotor muscles rather than solely by ventilatory constraints.
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This review highlights that exercise limitation in COPD is largely driven by impaired oxygen delivery to locomotor muscles, challenging the classical belief that it is solely due to ventilatory limits.
Published data indicate that exercise in COPD is more often limited by leg effort than breathlessness. This casts some doubt on the classical belief that inability to ventilate limits exercise performance. In fact, symptoms limiting exercise appear to be essentially the same in COPD and in health or congestive heart failure, where exercise is limited by inadequate energy supply to locomotor muscles. In COPD, impaired O₂ delivery to locomotor muscles is suggested by: (1) the O₂ cost (v̇O2) of breathing may be ∼50% of whole body v̇O2; (2) decreasing the work of breathing improves performance and v̇O2 of locomotor muscles, and (3) locomotor muscle v̇O2 is greater when it is the only muscle exercising than during whole body exercise. Excessive expiratory pressures when expiratory flow is limited may lead to decreased venous return and contribute importantly to exercise limitation.
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Aliverti et al. (2001) conducted a review in COPD. Exercise limitation mechanisms was evaluated. Exercise limitation in COPD is primarily driven by inadequate energy supply and impaired oxygen delivery to locomotor muscles rather than solely by ventilatory constraints.
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