The Use of a Just Noticeable Difference Approach to Improve Perceptual Acuity Ability in Male Runners.

We were interested in micro-variations in an athlete's psychophysical state that separate peak exertion from physiological collapse. Thus, we measured perceptual acuity in runners using a classic psychophysical approach, the just noticeable difference (JND) on two standard stimuli runs at treadmill speed corresponding to 70%VO_2max and 80%VO_2max. Thirty-four male runners (M age = 35.26, SD = 7.33 years) first performed a maximal treadmill test to determine the speed of a standard exercise bout for the JND trials. The JND trials consisted of four 5-minute running bouts on a treadmill with 5-minute rests between bouts. For bouts 1 and 3, participants ran at the standard stimuli pace, but for bouts 2 and 4, they adjusted their speeds to achieve a level of exertion at a JND above/below the SS. They achieved differences in the final 30 seconds of the VO₂ between each JND bout and the previous standard stimuli at just above (JND-A) and just below (JND-B) the JND perceived exertions. We used a Generalized Linear Model analysis to compare the JND-A and JND-B within and between ventilatory threshold groups (lower/higher) in absolute and relative VO₂ and in terms of the total JND magnitude. The magnitude of JND-A was greater than that of JND-B at 70%VO_2max and 80%VO_2max in absolute units (70%VO₂ Δ = 2.62; SE = 0.37; p < .001; 80%VO₂ Δ = 1.67; SE = 0.44; p = .002) and in relative units (70%VO_2max Δ = 4.70; SE = 0.66; p < .001; 80%VO_2max Δ = 2.96; SE = 0.80; p = .002). The total magnitude was greater in the 70%VO_2max trial than 80%VO_2max in absolute units (70%VO₂ M = 3.78, SE = 0.31 mL·kg^-1·min^-1; 80%VO₂ M = 2.62, SE = 0.37 mL·kg^-1·min^-1; p = .020) and in relative units (70%VO_2max M = 6.57, SE = 0.53%VO_2max; 80%VO_2max M = 4.71, SE = 0.64%VO_2max; p = .030). The JND range narrowed when physiologic demand increased, for both physical (speed) and psychological (RPE) variables.