Perceived exertion associated with breathing hyperoxic mixtures during submaximal work

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Abstract
The effect of an enriched inspired oxygen concentration on perceived exertion (RPE) was investigated while running at two submaximal treadmill loads. Twelve males ($o2 max = 49.3 ml/kg$min) worked at 50% and 80% $o2 max, breathing either air or 80% O2-20% N2 in random order using a single blind technique. Subjects were evaluated while running for 10 min and during a 20 min recovery. Heart rate (HR), ventilation ($E), respiration rate (RR), tidal volume (VT) and RPE were measured before, during and after work. Blood lactate was measured 1 min after work. Oxygen concentration did not statistically affect HR, VE, RR or VT during exercise or recovery. At both loads, RPE at the end of exercise was significantly reduced breathing the hyperoxic mixture. At 50% Vo2 max, mean RPE decreased from 11.2 breathing room air to 9.6 breathing 80% O2 and, at 80% Vo2 max, from 13.8 to 11.7 (P < 0.01). Blood lactates were significantly reduced breathing 80% O2; from 23.4 mg% to 13.3 at 50% Vo2 max and from 55.5 to 36.5 at 80% Vo2 max (P2 concentration and there is a significant relationship between RPE and blood lactate.