Optic Flow Influences Perceived Exertion and Distance Estimation but not Running Pace

Purpose: This study aimed to examine the effect of variations in optic flow on perceived and actual running pace and RPE. Methods: Twelve male moderately trained competitive runners performed a self-paced 5-km running reference time trial followed by a three 5-km running self-paced trials under different optic flow conditions (R-NORM = actual running speed, R-SLOW = actual speed - 25%, and R-FAST = actual speed + 25%). Participants were asked to self-report RPE when they thought they had reached each kilometer. Results: There was no difference in the 5-km completion times (P > 0.05) or actual pace (P > 0.05) between the optic flow conditions. A greater distance was covered between the perceived kilometer points during R-SLOW compared with R-NORM (P < 0.01) and R-FAST (P < 0.01). RPE (normalized for running distance) was lower during R-SLOW compared with R-NORM (P < 0.01) and R-FAST (P G 0.01). Conclusions: Different rates of optic flow lead to an apparent compression or elongation of perceived distance during running, with slow optic flow resulting in an increased ratio of perceived to actual running distance. Pacing was not different in the slow optic flow condition, despite lower perceived exertion, which is contrary to the predictions of the RPE template model, hazard scores, and estimated time limits.