Perceptual acuity ability in endurance runners: How cardiorespiratory fitness,not biological sex,shapes interoceptive awareness

Abstract

This study examined sex differences in perceptual acuity ability, quantified via the just-noticeable difference approach (JND), through $\dot{\mathrm{V}}$ O₂ kinetics expressed relative to individual $\dot{\mathrm{V}}$ O_2max, their relationship to time perception, rating of perceived exertion (RPE), speed, and heart rate (HR) in recreational runners. Sixty-four runners (Females: n = 30, $\dot{\mathrm{V}}$ O_2max = 48.0 ± 5.2 ml·kg⁻¹·min⁻¹; Males: n = 34, $\dot{\mathrm{V}}$ O_2max = 57.0 ± 5.6 ml·kg⁻¹·min⁻¹) completed a maximal estimation trial and four 5-min JND bouts at 70% $\dot{\mathrm{V}}$ O_2max, designed to quantify the $\dot{\mathrm{V}}$ O₂ difference during the final 30 s between each JND bout and the preceding standard stimulus at intensities perceived as just above (JND-A) and just below (JND-B) the reference exertion. $\dot{\mathrm{V}}$ O₂-time trajectories were modeled with generalized additive models; secondary outcomes were assessed via repeated-measures ANOVA. No sex differences emerged in total JND magnitude (Females: 6.83 ± 3.69% $\dot{\mathrm{V}}$ O_2max; Males: 6.23 ± 2.82% $\dot{\mathrm{V}}$ O_2max; d = 0.182) or time perception (η²_p = 0.009). Females exhibited higher $\dot{\mathrm{V}}$ O₂ (+3.54% $\dot{\mathrm{V}}$ O_2max) and distinct $\dot{\mathrm{V}}$ O₂-time trajectories. Independent of sex, JND-A elicited a greater magnitude of change than JND-B: higher relative $\dot{\mathrm{V}}$ O₂, RPE (Δ = 1.31–1.38 a.u.), time perception (Δ = 19–23.5 s), and speed (Δ = 0.096–0.134 m·s⁻¹). HR increased in JND-A for females (Δ=6.03 bpm) but not for males. These findings suggest that recreational runners of both sexes demonstrated comparable perceptual acuity ability, despite distinct relative $\dot{\mathrm{V}}$ O₂ responses. At the bout level, our findings indicate an asymmetric self-regulation pattern, with JND-A eliciting greater physiological and perceptual responses than JND-B. Coaches can utilize JND thresholds, which relate to perceptual acuity, to create training programs aimed at supporting interoceptive awareness and exercise intensity regulation in recreational runners.