Patterning Of Physiological And Perceptual Responses To Exercise

Abstract

The rating of perceived exertion (RPE), a subjective indicator of exercise intensity, is becoming increasingly popular for monitoring and prescribing exercise intensity in clinical populations. It remains unclear whether the relationship between RPE and oxygen uptake (VO2) is affected by perturbations to the sympathetic nervous system. PURPOSE: To determine whether acute sympathetic blockade alters the relationship between heart rate (HR), RPE and VO2 during incremental exercise. METHODS: Eleven healthy adults completed two graded exercise tests (GXT) on a motorized treadmill, under a β2 receptor antagonist and placebo. Treadmill speed increased by 2 km·h-1 every 2 min and participants reported their RPE (Borg 6-20 RPE Scale) each min until exhaustion. The VO2 and HR were measured continuously. Linear regression modelled the growth of individual participant relationships of RPE and HR with VO2. To account for differences in peak HR between conditions, values were expressed relative to the peak HR from each GXT. Paired sample t-tests assessed differences in the slope (b) of the individual regression models between conditions. RESULTS: The VO2peak and HRpeak were lower during β-blockade (51.9±5.3 vs 48.6±7.5 mL·kg-1·min-1, p<0.05; 192.7±8.2 vs 156.0±23.1 b·min-1, p<0.01, respectively). As expected, the slope for the relationship between HR and VO2 was greater during β-blockade (b 0.37±0.03 vs 0.48±0.07, p<0.01), however, there was no significant difference in the slope of the RPE:VO2 relationship (b 3.34±0.71 vs 3.30±0.77, respectively p>0.05) and no significant difference in b when HR was expressed relative to the peak HR during the GXT (b 0.71±0.07 vs 0.73±0.07, p>0.05). CONCLUSION: Despite a marginally lower VO2peak, the relationship between RPE and VO2 remains unchanged by sympathetic blockade, whereas the absolute HR:VO2 relationship is significantly altered. This means that RPE can be used in place of HR to determine metabolic work or estimate fitness sub-maximally in individuals taking β-blockade.