Steady-state acid-base response at exercise levels close to maximum lactate steady state

Area of Science:

• Exercise Physiology
• Sports Science
• Human Physiology

Background:

• Understanding acid-base balance during intense exercise is crucial for performance.
• The maximum lactate steady-state (MLSS) is a key indicator of endurance capacity.
• Previous studies have shown significant acid-base disturbances during maximal exercise.

Purpose of the Study:

• To investigate the acid-base status in capillary blood during a constant-load treadmill test.
• To examine physiological responses at exercise intensities close to the MLSS.
• To determine if acid-base balance is maintained at submaximal exercise intensities.

Main Methods:

• Two treadmill tests were conducted: one maximal and one steady-state.
• The steady-state test load was set at the mean of the two ventilatory thresholds.
• Capillary blood samples were analyzed for gases, metabolites, and electrolytes.

Main Results:

• Acid-base variables significantly decreased during the maximal test.
• Lactate concentrations exceeded those at the onset of blood lactate accumulation.
• During the steady-state test, only pH and PCO2 varied significantly; bicarbonate, potassium, chlorine, and sodium remained stable.

Conclusions:

• Acid-base status in capillary blood remained constant during a steady-state test at approximately 80% VO2max, even with lactate > 4 mmol/L.
• Despite stable acid-base status, other physiological variables did not remain constant.
• This suggests a complex interplay of factors regulating acid-base balance during prolonged, intense exercise.