Maximal lactate steady state does not correspond to a complete physiological steady state.

Area of Science:

• Exercise Physiology
• Sports Science
• Human Physiology

Background:

• The maximal lactate steady state (MLSS) is a key indicator of endurance capacity.
• It is often assumed to represent a complete physiological steady state during prolonged exercise.
• Verification of this assumption is crucial for accurate performance assessment.

Purpose of the Study:

• To determine if the maximal lactate steady state (MLSS) aligns with a true physiological steady state.
• To investigate physiological and metabolic responses during a 30-minute constant-load exercise at MLSS.

Main Methods:

• Eight trained male cyclists completed a 30-minute constant-load test at their predetermined MLSS on a cycle ergometer.
• Continuous monitoring of blood gases, lactate, acid-base balance, hematological parameters, and cardiorespiratory variables was performed.

Main Results:

• No significant changes were observed in arterial lactate, oxygen uptake, carbon dioxide output, or acid-base balance indicators (except pH) between 10 and 30 minutes.
• Significant increases in respiratory rate, heart rate, and decreases in arterial carbon dioxide pressure and pH were noted.
• Key parameters like oxygen uptake and gas exchange ratio remained stable, suggesting some steady-state characteristics.

Conclusions:

• The maximal lactate steady state (MLSS) does not represent a complete physiological steady state.
• Despite stable lactate and oxygen consumption, significant cardiovascular and respiratory adjustments occur.
• These findings necessitate a nuanced interpretation of MLSS in exercise physiology research and practice.