The individual rate of perceived exertion: an efficient method for monitoring training intensity in runners

Aim: Blood lactate concentration (BLC) and rating of perceived exertion (RPE) have been shown to be good markers of metabolic demand during exercise. The BLC can be anchored to intensity parameters (e.g., heart rate (HR) or running speed (S)) for runners in order to prescribe and to control training intensity. The aim of this study was to determine the agreement between intensity parameters predicted by BLC and individual rating of perceived exertion (RPEi) in amateur runners. Methods: Ninety-five amateur runners performed a test on a treadmill to determine intensity parameters at 2 mmol.L-1 (BLC2) and 4 mmolL-1 (BLC4) as tested levels (stage duration = 4’; pauses = 1’ to measure BLC; speed increment = 1.5 km.h-1/stage). The test started with an initial speed corresponding to the 70 % of the average speed attained during the last competition, while criterion to interrupt the test was the achievement of a BLC C 4 mmol.L-1. BLC, HR, S and RPE were recorded in every stage. RPEi corresponding to BLC2 (RPEi2) and BLC4 (RPEi4) were predicted for each volunteers. Subsequently, HR (bpm) and S (km.h-1) were predicted through the equation obtained from linear regression using fixed BLC and RPEi values as independent variables. Coefficient of determination (R2) was used to verify the goodness of fit of regressions. Bland and Altman plot was used to verify the agreement of the predicted values. Data are showed as mean ± SD. Results: The individual regressions between BLC and RPE showed high R2 (0.94 ± 0.065). Thus, RPEi2 (4.2 ± 1.0 a.u.) and RPEi4 (6.8 ± 1.1 a.u.) could be adequately predicted by the linear regression. The Bland and Altman showed that HR predicted by BLC2 and RPEi2 (bias = -0.07 ± 0.34 bpm; CL 95 % = ± 0.7 bpm), as well as by BLC4 and RPEi4 (bias = -0.5 ± 2.0 bpm; CL 95 % = ±3.9 bpm) showed excellent agreement. In the same way, S predicted by BLC2 and RPEi2 (bias = -0.01 ± 0.04 km.h-1; CL 95 % = ± 0.08 km.h-1), as well as by BLC4 and RPEi4 (bias = -0.05 ± 0.35 km.h-1; CL 95%= ± 0.69 km.h-1) also showed excellent agreement. Conclusions: RPEi showed comparable accuracy in relation to its correspondent BLC to predict intensity parameters (HR and S). This is significant evidence since RPE correspondent to fixed BLC do not change after training period.