Impact of dehydration on perceived exertion during endurance exercise: A systematic review with meta-analysis

Abstract

Background: Understanding the impact of stressors on the rating of perceived exertion (RPE) is relevant from a performance and exercise adherence/participation standpoint. Athletes and recreationally active individuals dehydrate during exercise. No attempt has been made to systematically determine the impact of exercise-induced dehydration (EID) on RPE.

Objective: The present meta-analysis aimed to determine the effect of EID on RPE during endurance exercise and examine the moderating effect of potential confounders.

Data analyses: Performed on raw RPE values using random-effects models weighted mean effect summaries and meta-regressions with robust standard errors, and with a practical meaningful effect set at 1 point difference between euhydration (EUH) and EID. Only controlled crossover studies measuring RPE with a Borg scale in healthy adults performing ≥30 min of continuous endurance exercise while dehydrating or drinking to maintain EUH were included.

Results: Sixteen studies were included, representing 147 individuals. Mean body mass loss with EUH was 0.5 ± 0.4%, compared to 2.3 ± 0.5% with EID (range 1.7-3.1%). Within an EID of 0.5-3% body mass, a maximum difference in RPE of 0.81 points (95% CI: 0.36-1.27) was observed between conditions. A meta-regression revealed that RPE increases by 0.21 points for each 1% increase in EID (95% CI: 0.12-0.31). Humidity, ambient temperature and aerobic capacity did not alter the relationship between EID and RPE.

Conclusion: Therefore, the effect of EID on RPE is unlikely to be practically meaningful until a body mass loss of at least 3%.

Keywords: Hydration; Hypohydration; Performance; RPE; Rating of perceived exertion.

Fig. 1

Flowchart showing the selection process used for the inclusion and exclusion of studies.

Fig. 2

(a) Changes in perceived exertion (means ± SD) occurring during exercise between the euhydrated control condition and the exercise-induced dehydration (EID) experimental condition across levels of exercise-induced dehydration of 0.5, 1, 1.5, 2, 2.5 and 3% body mass. (b) Forest plot showing the mean differences in perceived exertion across different levels of exercise-induced dehydration. Filled diamond symbols represent the weighted mean change in perceived exertion between conditions. Size of squares is proportional to the weight of each study. AU: arbitrary units. CI: confidence interval.

Fig. 3

(a) Slope estimates for the regression of perceived exertion on the % body mass loss for each of the included studies; (b) Forest plot combining all slope estimates to derive a weighted mean summary effect; (c) Relationship between perceived exertion and % body mass loss while including all study-specific data points. AU: arbitrary units. CI: confidence interval. RPE: rating of perceived exertion.

Fig. 4

Relationships between the changes in slope estimates and (a) temperature, (b) humidity level, (c) exercise duration, (d) exercise intensity, (e) aerobic capacity ($\dot{\mathit{V}}$O_2max) and mean (f) heart rate difference across the different studies included in the meta-analysis. Otherwise stated n = 16. CI: confidence interval. EID: exercise-induced dehydration (experimental condition). EUH: euhydration (control condition). RPE: rating of perceived exertion.