Low carbohydrate diet affects the oxygen uptake on-kinetics and rating of perceived exertion in high intensity exercise

The aim of this study was to determine if the carbohydrate (CHO) availability alters the rate of increase in the rating of perceived exertion (RPE) during high intensity exercise and whether this would be associated with physiological changes. Six males performed high intensity exercise after 48 h of controlled, high CHO (80%) and low CHO (10%) diets. Time to exhaustion was lower in the low compared to high CHO diet. The rate of increase in RPE was greater and the VO2 slow component was lower in the low CHO diet than in the control. There was no significant condition effect for cortisol, insulin, pH, plasma glucose, potassium, or lactate concentrations. Multiple linear regression indicated that the total amplitude of VO2 and perceived muscle strain accounted for the greatest variance in the rate of increase in RPE. These results suggest that cardiorespiratory variables and muscle strain are important afferent signals from the periphery for the RPE calculations.

Construct and Concurrent Validation of OMNI–Kayak Rating of Perceived Exertion Scale

This study tested the concurrent and construct validity of a newly developed OMNI–Kayak Scale, testing 8 male kayakers who performed a flatwater load-incremented “shuttle” test over a 500-m course and 3 estimation-production trials over a 1,000-m course. Velocity, blood lactate concentration, heart rate, and rating of perceived exertion (RPE), using the OMNI–Kayak RPE Scale and the Borg 6–20 Scale were recorded. OMNI–Kayak Scale RPE was highly correlated with velocity, the Borg 6–20 Scale RPE, blood lactate, and heart rate for both load-incremented test ( rs = .87–.96), and estimation trials ( rs = .75–.90). There were no significant differences among velocities, heart rate and blood lactate concentration between estimation and production trials. The OMNI–Kayak RPE Scale showed concurrent and construct validity in assessing perception of effort in flatwater kayaking and is a valid tool for self-regulation of exercise intensity.