Core-Perception Coupling: Relationships among Core Temperature, the Rating of Perceived Exertion, and Thirst during...

Area of Science:

• Exercise Physiology
• Sports Science
• Human Performance

Background:

• Hydration status is a known modulator of exercise performance and tolerance.
• Understanding the interplay between physiological and perceptual responses during exercise is essential for optimizing training and performance.
• Baseline hydration can influence how individuals perceive exertion and discomfort during physical activity.

Purpose of the Study:

• To investigate the relationships between core body temperature (Tc), ratings of perceived exertion (RPE), and thirst during moderate-intensity continuous cycling.
• To determine if baseline hydration status moderates these associations within a single exercise trial.
• To compare the effects of structured hydration counseling versus habitual fluid intake on exercise responses.

Main Methods:

• Thirty trained male participants completed a 120-minute cycling trial at 50% Wmax under thermoneutral conditions.
• Participants were randomized into a hydration counseling group (EXP) or a control group (CON) with habitual fluid intake.
• Urine specific gravity verified hydration status, while Tc, heart rate, RPE, and thirst were recorded periodically. Statistical analyses included repeated-measures tests, correlations, and ANCOVA.

Main Results:

• Ratings of perceived exertion (RPE) and thirst increased throughout the cycling trial, while core temperature (Tc) tended to plateau.
• Baseline hydration status was a significant predictor of higher RPE and thirst, independent of Tc.
• The hydration counseling group (EXP) showed significantly lower increases in RPE and thirst and were more likely to complete the full 120-minute trial compared to the control group (CON).

Conclusions:

• Starting exercise in a euhydrated state effectively reduces perceived effort and thirst during prolonged, thermoneutral cycling.
• Core body temperature alone has limited explanatory power for RPE when hydration status is considered.
• Simple physiological markers like thirst and heart rate can indicate emerging physiological strain, particularly in individuals with lower cardiorespiratory fitness (VO2max).