PULMONARY-FUNCTION RESPONSE TO EQUIVALENT DOSES OF OZONE CONSEQUENT TO INTERMITTENT AND CONTINUOUS EXERCISE

The effects on pulmonary function of inhaling the same effective dose of ozone, as well as subjective responses during continuous exercise and intermittent exercise, were studied in 12 aerobically trained men. Each subject completed 1 h of continuous exercise at work rates that elicited a mean minute ventilation of 60 l/min, and two additional 2-6 intermittent exercise exposures eliciting a mean exercise minute ventilation of 45-47 l/min (i.e., total minute ventilation for each protocol was approximately 3600 l). Subjects were exposed in randomized sequence to 0.30 ppm ozone on three occasions and to filtered air on three occasions. Forced expiratory volume in 1 s decrements of -17.6%, -17.0%, and -17.9%, respectively, for the 1-h continuous exercise exposure and the two 2-h intermittent exercise exposures to 0.30 ppm ozone were significantly different. Exposure to ozone caused significant differences between postexposure subjective symptom responses; that is, responses associated with continuous exercise were greater than those for either intermittent exercise protocol. However, the overall symptom severity responses during the last minute of exercise for the two intermittent exercise protocols (at 90 and 105 min, respectively) were not significantly different from the continuous exercise postexposure value. The findings indicate that when the ozone effective dose is equivalent at a given ozone concentration, there is no difference between pulmonary function responses to continuous exercise or intermittent exercise exposures of 2-h duration (or less), although subjective symptoms are reduced somewhat during the last rest period of intermittent exercise.