Exercise intensity has traditionally been described, prescribed and normalised as a fraction (%) of the maximal oxygen uptake ( V˙O (2max)). We hypothesised that the extent of inter-subject variability in the physiological responses to exercise would be greater when work rates were prescribed using % V˙O (2max) as compared to % 'delta' (Δ), a method of normalising exercise intensity in which both the gas exchange threshold (GET) and the V˙O (2max) are considered. 9 men completed a ramp incremental test on a cycle ergometer to establish the GET and V˙O (2max). Subsequently, subjects completed 6 constant-work-rate exercise bouts at intensities corresponding to: 50%, 70% and 90% V˙O (2max); and 60% GET, 40% Δ (that is, 40% of the difference between the GET and V˙O (2max)) and 80% Δ. For all bouts, exercise was continued for 20 min or until task failure if this occurred sooner. When exercise was prescribed using the % Δ concept, there were significant reductions in the inter-subject variability in pulmonary gas exchange, blood lactate accumulation, heart rate, and ratings of perceived exertion (all P < 0.05). In conclusion, the % Δ concept resulted in more consistent inter-subject physiological responses to constant-work-rate exercise and should be used in preference to % V˙O (2max) to more effectively normalise exercise intensity.
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