Abstract
PURPOSE: We examined the effect of β-blockade on measures and reproducibility of heart rate (HR), oxygen uptake ( V˙O2 ) and work rate (WR) across repeated bouts of short-duration, RPE-regulated exercise. METHODS: Participants completed an RPE-regulated, interval-based exercise session under control and β-blockade conditions with six 3-min bouts alternating between RPE 13 and RPE 15, separated by 2-min active recovery periods. Participants adjusted treadmill speed/grade to meet the target RPE. Linear mixed effects models assessed the effect β-blockade on exercise responses for each RPE, while intraclass correlation coefficients (ICC) and coefficients of variation (CV) evaluated reproducibility across bouts. RESULTS: β-Blockade significantly reduced HR (- 36.5 beat min(-1), p < 0.001), V˙O2 (- 4.2 mL kg(-1) min(-1), p < 0.001) and work rate (- 0.6 METs, p = 0.022) during exercise. Differences between conditions remained significant for %HR(peak) (p < 0.001) but not % V˙ O(2peak) or %WR(peak) (p > 0.05). Exercise responses were consistently higher at RPE 15 than RPE 13 (all p < 0.001). A significant interaction showed greater HR reduction at RPE 15 (45.5 beat min(-1)) than RPE 13 (40.0 beat min(-1)) under β-blockade (p = 0.041). ICC values indicated good to excellent reproducibility across bouts, with no significant difference between conditions. Variability across bouts was low (mean CV = 2-8%) and unaffected by β-blockade. CONCLUSION: Our findings suggest that despite significant reductions in absolute responses, β-blockade does not affect relative measures of V˙ O(2) or work rate. RPE-regulated exercise may facilitate highly reproducible exercise intensities, making it particularly valuable for populations where β-blocker use is prevalent.