Impaired exercise performance and pulmonary function in elite cyclists during low-level ozone exposure in a hot environment.

We evaluated the effects of low concentrations of ozone on the exercise performance and pulmonary function of 17 top-caliber endurance cyclists under conditions simulating competition and realistic temperature (31 degrees C). Each subject was randomly exposed to filtered air (FA), 0.12 and 0.20 ppm O3 on separate days in an environmental chamber. Each subject attempted to maintain submaximal exercise on a cycle ergometer equivalent to approximately 70% of maximal oxygen consumption (VO2max) for 60 min, followed by incremented (maximal) exercise until exhaustion. During submaximal exercise, average minute ventilation (VE) (89 L/min), VO2 (51 ml/min/kg or 72% VO2max), work load (260 W), and work time (57 min) were similar across all exposures. During maximal exercise, average peak VE (150 L/min), VO2 (68 ml/min/kg), work load (382 W), and ride time (263 s) were similar between 0.12 ppm O3 and FA. However, significant reductions in peak VE (18%), VO2 (16%), tidal volume (22%), work load (8%), and ride time (30%) occurred in 0.20 ppm O3 compared with those in FA. Postexercise decrements in forced expired volume in one second (FEV1) averaged 5.6% and 21.6% in 0.12 and 0.20 ppm O3, respectively. Ozone-related symptoms were mild in 0.12 ppm O3 but intensified and probably limited maximal performance in 13 subjects in 0.20 ppm O3. Changes in carbon monoxide diffusing capacity (adjusted for alveolar volume) were not significant across exposures. Nine subjects showed histamine hyperresponsiveness (i.e., greater than 20% decrease from the control postdiluent FEV1) after exposure to 0.20 ppm O3 as compared with 1 subject in 0.12 ppm O3.(ABSTRACT TRUNCATED AT 250 WORDS)