Sex difference in fluid balance responses during prolonged exercise.

Area of Science:

• Exercise Physiology
• Sports Science
• Human Physiology

Background:

• Maintaining fluid balance is critical for athletes to prevent dehydration during exercise.
• The influence of sex on fluid balance during prolonged exercise remains under-researched.

Purpose of the Study:

• To compare body mass changes and fluid balance parameters between men and women during prolonged moderate-intensity exercise.
• To investigate the role of sex in regulating fluid balance during endurance activities.

Main Methods:

• Ninety-eight volunteers completed a 30-50 km walk at a self-selected pace.
• Body mass changes, fluid intake, fluid loss, and blood sodium levels were measured.
• Exercise duration (approx. 8.5 hours) and intensity (69% HRmax) were consistent between groups.

Main Results:

• Men exhibited significantly greater body mass loss (-1.6%) compared to women (-0.9%).
• Men had a higher incidence of dehydration (≥ 2% body mass loss) (34% vs 12%) and postexercise hypernatremia (27% vs 0%).
• Men showed lower fluid intake (2.9 mL/kg/h) and higher fluid loss (5.0 mL/kg/h) than women.

Conclusions:

• Men and women exhibit distinct fluid balance responses to prolonged exercise.
• Sex is a significant factor influencing dehydration risk and fluid regulation during endurance activities.
• Further research is needed to understand the physiological mechanisms underlying these sex-based differences.