Cohen, J., Foster, C., de Koning, J. J., Wright, G., Doberstein, S. T., & Porcari, J. P. (2011). Breaking away: Effects of non-uniform pacing on power output and RPE growth. Medicine and Science in Sports and Exercise, 43(5). Supplement abstract 811.

This study determined if power output would decrease when the rating of perceived exertion was forced above the normal growth curve during a cycling time-trial. Well-trained, task-habituated cyclists (M = 6, F = 4) performed two, randomly ordered, l0 km cycle (Velotron) time-trial simulations. In one trial (Control), they rode at their own best pace throughout. In the other Burst trial, they were instructed (without previous warning) to make a 1 km "burst" at the 4 km mark, and then finish as rapidly as possible.

The Control ride was significantly faster than the burst trial. During the Control ride, responses between 4-5 km were: Power 240 W; RPE 5-6; and lactate 8-9 mmol. During the Burst trial, Power increased to 290 W, then fell to 220 W following the burst, and remained low until the beginning of the end spurt at 9 km. RPE increased to 9 during the Burst, but returned to the normal RPE growth pattern at 6 km. Lactate increased to 13 mmol following the burst, and remained elevated throughout the remainder of the trial.

Implication. The somewhat reciprocal behavior of rating of perceived exertion and power during the burst trial provides partial support for the hypothesis that RPE functions as the translator between the brain and the body during heavy exercise. However, the continuing reductions of power following the burst, even after RPE had returned to its normal pattern of growth during a time-trial, suggests that power is regulated in a more complex manner than reflected by RPE.

The cost of an increase in effort level during a relatively even-paced effort is particularly high and detrimental to performance and post-burst physiological functioning.

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