Body Composition Changes During a 24-h Winter Mountain Running Race Under Extremely Cold Conditions

Area of Science:

• Exercise Physiology
• Environmental Extremes
• Sports Science

Background:

• No prior research has investigated body composition, skeletal muscle damage, or renal function in ultra-endurance runners during 24-hour races in extreme cold (-14.3°C).
• Understanding physiological responses to such extreme conditions is crucial for athlete safety and performance optimization.

Purpose of the Study:

• To assess changes in body composition (body fat, skeletal muscle mass, total body water) in runners during a 24-hour winter race.
• To evaluate markers of skeletal muscle damage (creatine kinase) and renal function (plasma urea, plasma creatinine, creatinine clearance) under extreme cold conditions.

Main Methods:

• Twenty finishers of a 24-hour winter race (14 men, 6 women) underwent pre- and post-race assessments.
• Measurements included anthropometrics, plasma urea (PU), plasma creatinine (Pcr), creatine kinase (CK), plasma volume (PV), and total body water (TBW).

Main Results:

• Male runners experienced significant decreases in body mass and body fat; skeletal muscle mass and total body water remained stable.
• Female runners showed a significant decrease in body fat, with stable body mass, skeletal muscle mass, and total body water.
• Plasma volume, CK, Pcr, and PU increased significantly, while creatinine clearance decreased, indicating skeletal muscle damage and transient renal impairment.

Conclusions:

• A 24-hour race in extreme cold significantly reduces body fat while preserving skeletal muscle mass and total body water.
• Elevated CK, Pcr, and PU levels correlate with skeletal muscle damage and transiently impaired renal function in these athletes.
• The study highlights the physiological stress of extreme cold on ultra-endurance runners, affecting muscle and kidney function.