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Differences between the cardiopulmonary exercise test with the highest and the exercise test with the lowest maximum oxygen uptake (VO2max) during the day (i.e., diurnal variation) and between the two exercise test taking place at the same time of the day (i.e., day-to-day variation). Values are presented for VO2max in ml/kg/min (A) and l/min (B). Square, mean difference; triangles, males; circles, females.
