The use of aero style handlebars has gained popularity in triathlons and individual time trial events recently. The effect of using these handlebars has only been examined during short term exercise. It was the aim of this investigation to compare time to exhaustion and selected measures of ventilation, gas exchange and pulmonary function when using aero style handlebars versus standard racing style handlebars during long term exercise. Eleven well trained cyclists with a VO2max of 61.7 +/- 2.9 ml.kg-1.min-1 completed two continuous rides at 80 to 95 percent of their VO2max. Subjects rode at 80% of their VO2max for one hour and the work rate was increased by 5% of their VO2max every 15 min thereafter. The rides were completed with the subject riding his/her personal bicycle on a Velodyne trainer and differed in that during one ride the subjects rode with aero style handlebars and during the other they rode with standard racing style handlebars. During the ride with standard racing style handlebars, subjects rode with their hands on top of the bars or on the hoods of the brake levers. The subjects rode with the standard racing handlebars for 69.3 +/- 5.3 minutes as compared to 59.8 +/- 7.0 minutes with the aero style handlebars. This difference was not statistically significant. The average work rates when the cyclists terminated the exercise bouts with the aero and standard racing handlebars were 268.1 +/- 38.4 and 276.4 +/- 39.3 watts and were not significant from one another. Gas exchange and ventilatory parameters were measured every 15 min during the exercise bouts.(ABSTRACT TRUNCATED AT 250 WORDS)