Changes in blood pH, lactate concentration and pulmonary ventilation during incremental testing protocol on cycle...

Area of Science:

• Exercise Physiology
• Biochemistry
• Respiratory Physiology

Background:

• Understanding the regulation of blood pH during exercise is crucial for interpreting physiological responses.
• Lactate acidosis and respiratory compensation are key factors influencing acid-base balance during physical exertion.

Purpose of the Study:

• To investigate the relationship between blood lactate concentration ([LA]), blood pH, and pulmonary ventilation (VE) during incremental exercise.
• To identify distinct phases in the VE/[LA] ratio and their correlation with blood pH and exercise intensity.
• To explore individual differences in blood pH regulation and their link to endurance capacity.

Main Methods:

• Seven healthy subjects performed an incremental cycle ergometer test.
• Measurements included blood lactate concentration ([LA]), blood pH, and pulmonary ventilation (VE).
• The ratio of VE/[LA] was calculated and analyzed across different exercise intensities and pH levels.

Main Results:

• The VE/[LA] ratio exhibited three distinct phases during incremental exercise.
• Phase 1: Ratio increased with stable [LA] and pH.
• Phase 2: Ratio decreased as [LA] increased more than VE, followed by a drop in pH, with individual variations in regulation.
• Phase 3: VE/[LA] and pH stabilized, with negligible inter-subject differences.
• Trends in VE/[LA] correlated with the Onset of Blood Lactate Accumulation (OBLA) at pH < 7.32.

Conclusions:

• Blood pH regulation via respiratory compensation of lactate acidosis is more effective in individuals with higher endurance (higher OBLA).
• This enhanced regulation is most evident during slight increases in [LA] or mild acidosis.
• The study provides insights into the physiological mechanisms underlying acid-base balance during strenuous exercise.