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The aim of the study was to evaluate the power output during a multistage professional road race using direct power measurements and to compare these results with the performance measurements using competition heart rate recordings.Six professional road cyclists performed an incremental cycling test during which peak power output, power output, and heart rate at the lactate threshold (LT) and at a lactate increase of 1 mM above the LT (LT + 1) were assessed. During a six-stage road race competition, power output was measured directly (SRM crankset). To analyze the time spent at different intensities during competition, the amount of competition time spent below LT (zone 1), between the LT and LT + 1 (zone 2), and above LT + 1 (zone 3) determined during laboratory testing were calculated for power output and heart rate.During the five mass start stages, a mean power output of 220 ± 22 W (3.1 ± 0.2 W·kg−1) with a mean heart rate of 142 ± 5 bpm was measured. Average power output during an uphill time trial was 392 ± 60 W (5.5 ± 0.4 W·kg−1) with a mean heart rate of 169 ± 3 bpm. For the mass start stages, the average distribution of exercise time spent in different intensities calculated for power output and heart rate was 58 versus 38% for zone 1, 14 versus 38% for zone 2, and 28 versus 24% for zone 3.Most of the competition time during the mass start stages was spent at intensities near the LT. Compared with power output, heart rate measurement underestimated the time spent at intensity zones 1 and 3, and overestimated the time spent in zone 2.