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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%VO2max and 80%VO2max. 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%VO2max and 80%VO2max 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%VO2max Δ = 4.70; SE = 0.66; p <.001; 80%VO2max Δ = 2.96; SE = 0.80; p =.002). The total magnitude was greater in the 70%VO2max trial than 80%VO2max 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%VO2max M = 6.57, SE = 0.53%VO2max; 80%VO2max M = 4.71, SE = 0.64%VO2max; p =.030). The JND range narrowed when physiologic demand increased, for both physical (speed) and psychological (RPE) variables. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine physiological, perceptual, and affective responses during self-paced walking for three age groups. 66 adult women were assigned into three groups by age: 20-25 yr. (n = 22), 30-35 yr. (n = 22), and 40-45 yr. (n=22). Each participant completed a maximal exercise test and a 20-min. bout of walking at a self-selected pace. The preferred walking speed was similar for all age groups, whereas physiological responses relative to maximal and ventilatory threshold values were greater in the 40-45 yr. group than the other two groups. Nevertheless, perceptual and affective responses were similar for all age groups. These findings suggest that physiological responses, but not perceptual and affective responses, of sedentary women are associated with age during walking at a self-selected pace. [ABSTRACT FROM AUTHOR]