Fluctuating dynamics of perceived exertion in constant-power exercise

Objectives: To reveal and study the fluctuating dynamics of perceived exertion (PE) during constant-power exercise performed under different conditions (duration, intensity, and termination). Design: A pilot and two subsequent experimental studies were performed. The studies consisted of manipulating workload and measuring fluctuating perceived exertion dynamics throughout the cycling task. Methods: In a pilot study Borg's rating of perceived exertion (RPE) was measured every 15s in 2 groups of 9 participants each (using RPE 6-20 and CR10 scales, respectively) cycling at heavy intensity until volitional exhaustion. The percentage of participants alternating increased and decreased RPE values (fluctuating dynamics) was calculated. In 2 subsequent experiments PE changes (increase/decrease perceptions) were reported when occurring in 2 groups of 13 participants cycling at a moderate intensity for 30 and 60min, respectively (Experiment 1), and in another group of 12 participants cycling at heavy intensity until volitional exhaustion (Experiment 2). The individual time series of "increase"/"decrease" reports were divided into 5 non-overlapping temporal windows, and the percentages of "PE increase" were calculated for each window. Results: In the pilot study 66.6% (RPE 6-20 group) and 33.3% (CR10 group) of the participants showed an RPE fluctuating dynamics during the exercise. However, all participants showed a clear PE fluctuating dynamics during the moderate and heavy intensity exercises performed in Experiment 1 and Experiment 2, respectively. Nevertheless, a transition towards a PE non-fluctuating dynamics (dominated by "PE increase" reports) was noticed in Experiment 2 while approaching volitional exhaustion. Conclusions: PE seems to have a dominant fluctuating dynamics during constant-power cycling performed under different conditions (duration, intensity, and termination) that changes towards a non-fluctuating dynamics when approaching the volitional exhaustion point.