Pacing Differs Between Time- and Distance-Based Time Trials in Trained Cyclists.

The purpose of this study was to compare the pacing profiles between distance- and duration-based trials of short and long duration. 13 trained cyclists completed two time-based (6 min and 30 min) and two distance-based (4 km and 20 km) self-paced cycling time trials. Participants were instructed to complete each trial with the highest average power output. Ratings of perceived exertion (RPE) were measured throughout the trials. Average power output was not different between the 4 km and 6 min trials (324 ± 46 vs 325 ± 45 W; P=0.96), nor between the 20 km and 30 min trials (271 ± 44 vs 267 ± 38 W; P=0.24). Power output was greater upon commencement of the distance-based trials when short and long trials were analysed together. Further, the rate of decline in power output over the first 40% of the trial was greater in the 20 km trial compared with the 30 min trial (P=0.01), but not different between the 4 km and the 6 min trials (P=0.13). RPE was greater in the 4 km trial compared with the 6 min trial, but not different between the 20 km and 30 min trials. These findings indicate that athletes commenced distance-based time trials at relatively higher power outputs when compared with a similar time-based trial. Such findings may result from discreet differences in our ability to judge or predict an exercise endpoint when performing time- and distance-based trials.