Just Noticeable Difference in Perception of Physical Exertion: Relation with Ventilatory Breakpoint and Vo2peak

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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: Recreationally active males (n=20) and females (n=26) (age 21.4±3.1 yr) 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 min. 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 resistance to achieve a level of exertion above or below the standard. The difference in final 30-s VO2 between each JND bout and the previous standard was taken as the physiologic analog of the above (ΔJND-A) and below (ΔJND-B) perceived exertion JND, expressed in absolute (l·min-1) and relative (%VO2PEAK) values. ΔJND-A and ΔJND-B were compared between genders, as well as between subjects exhibiting lower and higher ventilatory breakpoints (Vpt) and VO2PEAK within genders. RESULTS: For the total sample, ΔJND-B was significantly greater (p<0.05) than ΔJND-A when expressed in absolute (0.24±0.20 l·min-1 vs. 0.17±0.13 l·min-1, respectively) and relative values (8.33±6.01 %VO2PEAK vs. 5.90±4.09 %VO2PEAK, respectively). For both males and females, there were no differences in JND values between subjects with lower and higher Vpt or VO2PEAK. CONCLUSION: It is proposed that the VO2 corresponding to a JND above and below a standard stimulus can serve as an effective tool to measure a subject's perceptual acuity. This can be used to determine an individual's ability to accurately self-regulate prescribed exercise intensities. (This is a secondary analysis of a previously reported data set which has been expanded.)