LAUSR

Exercise intolerance is a hallmark of severe chronic obstructive pulmonary disease (COPD), resulting from early onset of breathlessness and fatigue on exertion, due in turn to impaired oxygen uptake, reduced cardiovascular fitness and skeletal muscle dysfunction.1 Exercise tolerance can be improved by aerobic and resistance training, which is typically packaged as part of pulmonary rehabilitation. Nonetheless, not everyone may benefit due to issues with poor uptake and completion, particularly in very severe disease2 or following acute exacerbations,3 and response isheterogeneous.2 Furthermore, symptom burden may restrict patients’ ability to perform whole body exercise at the intensity needed to induce meaningful physiological adaptations. Interest in neuromuscular electrical stimulation (NMES) as an alternative training modality in severe COPD has therefore grown steadily since early studies at the turn of the century.4,5 There is now convincing evidence that NMES provides a valid stimulus to cause muscle adaptions,6 and placebo-controlled data support a secondary effect on exercise tolerance.7 But how does NMES compare to classic forms of training? And where might this modality fit in the exercise toolkit when supporting patients with severe disease? Here we consider NMES studies with active comparator, usually another training modality, to begin to understand a role for this modality in practice and suggest possibilities for the next generation of studies in this field.