Mendelson M, et al. - Researchers performed a systematic review of studies assessing peak oxygen consumption (VO_2peak) of obstructive sleep apnoea (OSA) patients in mL·kg^-1·min^-1 compared with controls or in % predicted, to synthesize the existing data regarding VO_2peak in patients with OSA. The studies were analyzed, the data was extracted and the quality of evidence was evaluated by two independent reviewers. Reduced maximal aerobic capacity was noted in OSA patients. In certain patient subgroups, reduced maximal aerobic capacity could be seen to have an association with increased cardiovascular risks and reduced survival. In order to characterize functional limitation as well as to assess health status in OSA patients, the utility of maximal exercise testing was suggested.