Breaking Away: Effects Of Non-uniform Pacing On Power Output And Rpe Growth

Abstract

RPE normally grows as a scalar function of relative competitive distance during fixed duration time trials; suggesting that it may be the 'translator' between the brain and the body relative to managing fatigue during heavy closed-loop exercise. From this, one predicts that there would be a reciprocal relationship between changes in momentary RPE and changes in muscular power output. PURPOSE: To determine whether power output would decrease when the RPE was forced above the normal growth curve during a cycle time trial. METHODS: To test this concept, well-trained, task-habituated cyclists (m=6, f=4, POmax=4.6 W·kg-1) performed two, randomly ordered, 10km cycle (Velotron) time-trial simulations. In one trial (Control), they rode at their own best pace throughout. In the other trial, the were instructed (without previous warning) to make a 1km 'burst' at the 4km mark, and then finish as rapidly as possible. RESULTS: The Control ride was significantly faster than the burst trial (16:37 vs 17:00). During the Control ride, responses between 4-5km were: PO: 240W, RPE:5-6, [HLa]:8-9 mmol·l-1. During the Burst trial, PO increased to 290W, then fell to 220W following the burst, and remained low until the beginning of the endspurt at 9km. RPE increased to 9 during the burst, but returned to the normal RPE growth pattern by 6 km; [HLa] increased to 13 mmol·l-1 following the burst, and remained elevated throughout the remainder of the trial. CONCLUSIONS: The somewhat reciprocal behavior of RPE and PO during the burst trail 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 PO following the burst, even after RPE had returned to it's normal pattern of growth during a time trial suggests that PO is regulated in a more complex manner than reflected by RPE.