Reliability Of Metabolic Thresholds And The Associated Ratings Of Perceived Exertion

Ratings of perceived exertion (RPE) are commonly used to prescribe and monitor exercise intensities appropriate to elicit cardiorespiratory adaptations. The gas exchange threshold (GET) and respiratory compensation point (RCP) provide information about the relative metabolic intensity of exercise. Determining the RPE associated with these thresholds may improve individual exercise prescriptions. PURPOSE: To examine the test-retest reliability of the GET and RCP as well as the RPE at the GET (GETRPE) and RCP (RCPRPE) from two graded exercise tests (GXT). METHODS: Nine men (mean ± SD, age = 24 ± 4 years, weight = 80.0 ± 9.26 kg, VO2peak = 45.7 ± 8.0 mL·kg-1·min-1) completed two cycle ergometry GXTs to determine the GET and RCP. Each GXT started at 80 W with 30 W increases every 2-min until a pedal cadence of 70 rev·min-1 could not be maintained. RPE was recorded after each 2-min stage. The GET and RCP were determined from visual inspection as the point of departure from linearity of the VCO2 versus VO2 and VE vs VCO2 relationships, respectively. Linear regression of the VO2 versus RPE relationship was used to determine the GETRPE and RCPRPE. Analyses included paired samples t-tests (p ≤ 0.05), intraclass correlation coefficients (ICC2,1), standard errors of measurement (SEM), coefficients of variation (CoV), and minimal differences (MD). RESULTS: There were no significant differences between test 1 (T1) and test 2 (T2) for the RPEGET (T1 = 13 ± 2, T2 = 13 ± 2, p = 0.33), RPERCP (T1 = 16 ± 1, T2 = 17 ± 1, p = 0.12), GET (T1 = 30.1 ± 8.6 mL·kg-1·min-1, T2 = 28.3 ± 7.1 mL·kg-1·min-1, p = 0.07), or RCP (T1 = 38.0 ± 8.6 mL·kg-1·min-1, T2 = 38.7 ± 7.1 mL·kg-1·min-1, p = 0.48). The RPERCP (ICC = 0.504, SEM = 0.8, MD = 2.2, CoV = 5.0%) exhibited “poor” reliability. However, “excellent” reliability was demonstrated for the RPEGET, (ICC = 0.820, SEM = 0.8, MD = 2.1, CoV = 6.1%), GET (ICC = 0.935, SEM = 1.8 mL·kg-1·min-1, MD = 5.0 mL·kg-1·min-1, CoV = 6.2%), and RCP (ICC = 0.939, SEM = 2.0 mL·kg-1·min-1, MD = 5.5 mL·kg-1·min-1, CoV = 5.2%). CONCLUSIONS: The RPEGET and RPERCP reflect the perceptual intensities associated with the unique physiological responses at the GET and RCP, respectively, and may be used to assign training intensities. However, the RPERCP may not be as sensitive to indicate changes in the RCP across time, given its relatively poor reliability.