ATriple Iron triathlon leads to a decrease in total body mass but not to dehydration.

Area of Science:

• Sports Science
• Human Physiology
• Exercise Metabolism

Background:

• Ultraendurance events like the Triple Iron triathlon present unique physiological challenges.
• Body mass loss during prolonged exercise is often incorrectly attributed solely to dehydration.

Purpose of the Study:

• To quantify changes in total body mass, fat mass, and skeletal muscle mass in ultratriathletes.
• To assess hydration status markers before and after a Triple Iron triathlon.
• To investigate the relationship between body composition changes and hydration markers.

Main Methods:

• 31 male nonprofessional ultratriathletes were studied.
• Body mass, fat mass, skeletal muscle mass, and hydration markers were measured pre- and post-race.
• Statistical analysis was used to determine significant changes and associations.

Main Results:

• Total body mass decreased by 1.66 kg, skeletal muscle mass by 1.00 kg, and fat mass by 0.58 kg.
• No significant changes were observed in total body water or urinary specific gravity.
• Plasma urea increased significantly, correlating with skeletal muscle mass loss.

Conclusions:

• Completing a Triple Iron triathlon results in significant loss of both fat mass and skeletal muscle mass.
• Dehydration is not the primary cause of body mass loss in this ultraendurance event.
• Increased plasma urea suggests skeletal muscle breakdown contributes to mass loss.