Introduction:The traditional maximal oxygen uptake (VO2max) protocol has received criticism for being an unnatural form of excercise, lacking ecological validity and producing different VO2max responses depending on protocol duration and work rate increments.Purpose The purpose of this investigation was to design and test a new VO2max protocol allowing subjects to self-pace their work rate while maintaining an incremental test structure.Methods 16 untrained subjects completed a self-paced VO2max protocol (SPV) and a traditional VO2max test in a counter-balanced, crossover design. The SPV used incremental 'clamps' of ratings of perceived exertion (RPE) over 5 x 2-min stages (10-min duration) while allowing subjects to vary their power output (PO) according to the required RPE.Results Subjects achieved significantly higher (p < 0.05) VO2max values (40 +/- 10 ml/kg/min vs 37 +/- 8 ml/kg/min) and peak POs (273 +/- 58 W vs 238 +/- 55 W) in the SPV. Higher VO2max values were observed in the SPV even when a plateau (VO2-time slope < 0.05 l/min) occurred in the traditional test. No differences were found between any other measured physiological variable (minute ventilation, heart rate and respiratory exchange ratio).Conclusions As SPV is a closed-loop test (10-min duration) that allows subjects to self-pace their work rate, it disregards the need for experimenters to estimate starting work rates, stage lengths and increments in order to bring about volitional exhaustion in 8-10 min. The observation that the SPV may also elicit higher VO2max values than a traditional test warrants further research in this area and its consideration as standard measure to elicit VO2max.