Prescribed Drinking Leads to Better Cycling Performance than Ad Libitum Drinking.

Area of Science:

• Exercise Physiology
• Sports Science
• Environmental Physiology

Background:

• Dehydration during exercise, often exceeding 1-3% body weight loss, negatively impacts performance.
• Ad libitum (AD) fluid intake during prolonged exercise frequently leads to significant dehydration.
• Optimizing hydration strategies is crucial for athletes competing in hot conditions.

Purpose of the Study:

• To investigate the impact of a prescribed hydration protocol (PD) that matches fluid losses on simulated 30-km criterium-like cycling performance in the heat (31.6°C).

Main Methods:

• Ten elite male cyclists completed a 30-km criterium simulation in the heat under two conditions: AD drinking and PD drinking.
• Fluid losses were calculated during a familiarization trial to inform the PD protocol.
• Performance was assessed by mean cycling speed, with physiological measures including body temperature and sweat sensitivity recorded.

Main Results:

• Participants experienced significantly less dehydration under PD (-0.5% body weight) compared to AD (-1.8% body weight).
• Mean cycling speed during the final 5-km hill climb was 5.1% faster in the PD trial.
• Higher gastrointestinal, mean skin, and mean body temperatures were observed in the AD trial, alongside lower sweat sensitivity.

Conclusions:

• Prescribed hydration that matches fluid losses offers a performance advantage during prolonged exercise in the heat.
• This hydration strategy reduces thermoregulatory strain and enhances physiological responses like sweating.
• Optimizing fluid intake is critical for maintaining performance and mitigating physiological stress in hot environments.