Sex-Related Differences in the Maximal Lactate Steady State

Area of Science:

• Exercise Physiology
• Sports Science
• Human Performance

Background:

• Maximal lactate steady state (MLSS) is a key determinant of aerobic performance.
• Understanding sex differences in physiological responses at MLSS is crucial for optimizing training.

Purpose of the Study:

• To investigate sex differences in oxygen consumption (VO₂), heart rate (HR), and respiratory exchange ratio (RER) at MLSS in well-trained distance runners.
• To determine if MLSS represents a similar relative training intensity for both sexes.

Main Methods:

• Twenty-two well-trained runners (12 female, 10 male) underwent multiple 30-min steady-state runs to determine MLSS.
• Blood lactate and respiratory gas exchange measures were collected during steady-state runs.
• Time-to-exhaustion (TTE) runs at MLSS were performed to assess training intensity.

Main Results:

• Relative intensity at MLSS was similar between sexes for VO₂ (83% VO₂max) and HR (89% HRmax).
• Female runners exhibited a significantly lower RER at MLSS (0.84) compared to males (0.88).
• No significant difference was found in TTE at MLSS between males (79 min) and females (80 min).

Conclusions:

• While RER suggests different metabolic states at MLSS between sexes, the relative training load appears comparable.
• Sex-specific RER-derived estimates for MLSS are recommended for accurate training prescription.
• MLSS is a valuable and similarly applicable training intensity marker for both male and female distance runners.