Just Noticeable Difference In Perception Of Physical Exertion And Its Relation With The Ventilatory Breakpoint
Luke Haile, Maressa Priscila Krause, Ryan J. Mays, Suzette R. Bossart, Elizabeth F. Nagle, Fredric L. Goss, Robert James Robertson · Medicine & Science in Sports & Exercise · 2009
The just noticeable difference (JND) in the sensory response to conjunctively presented stimuli is a widely applied psychophysical measurement. However, little is known about the JND in the perception of physical exertion. PURPOSE: To describe the JND in the perception of physical exertion during submaximal cycle ergometer exercise. METHODS: Twelve recreationally active (≤150 min·wk-1 activity) males (age, 21.3±3.0 yr; VO2PEAK, 3.06±0.42 l·min-1) performed cycle exercise terminating at peak intensity. Rating of perceived exertion [RPE, OMNI Cycle (0-10) Scale] was estimated for the overall-body at the end of each minute. Individual linear regression was used to derive the power output (PO) and oxygen consumption (VO2) corresponding to an RPE of 5. This PO served as the standard. On a separate occasion, four 5-min cycle exercise bouts were performed with 5 min rest between bouts. During bouts 1 and 3, subjects cycled at the standard. During bouts 2 and 4, subjects adjusted the PO until the level of exertion was just noticeably above or below that of the standard. The difference in final 30-s VO2 between each JND bout and its yoked standard was taken as the physiologic analog of the above (DJND-A) and below (DJND-B) perceived exertion JND. DJND-A and DJND-B were compared within subjects using a paired-samples t-test. In addition, DJND-A, DJND-B, and the JND Range were compared between subjects with a low and high ventilatory breakpoint (Vpt). RESULTS: The mean (±SD) DJND-A was 0.19 (±0.13) l·min-1 (range, 0.06-0.52 l·min-1) and the DJND-B was 0.24 (±0.21) l·min-1 (range, 0.01-0.76 l·min-1). There was no difference between DJND-A and DJND-B. Subjects with a high Vpt had a larger DJND-B compared to subjects with a low Vpt (p<0.05). CONCLUSIONS: It is proposed that the VO2 corresponding to a JND above and below a standard stimulus can serve as a perceptual range in which subjects can accurately self-regulate a prescribed exercise intensity. Future research should determine if the perceived exertion JND varies with exercise intensity/mode, fitness, gender, and clinical status.