Exercise-induced changes in plasma potassium and the ventilatory threshold in man

Area of Science:

• Exercise Physiology
• Human Physiology
• Biochemistry

Background:

• The ventilatory threshold during incremental exercise is often linked to changes in ventilation (VE) and arterial potassium (Ka+).
• It has been hypothesized that alterations in Ka+ may influence peripheral chemoreceptors, triggering the ventilatory threshold phenomenon.

Purpose of the Study:

• To investigate whether the observed pattern of change in arterial potassium (Ka+) can account for the ventilatory threshold during incremental exercise.
• To examine the relationship between Ka+ and ventilatory threshold under both normal and lactic acidosis conditions.

Main Methods:

• Six healthy males performed incremental exercise tests under control and lactic acidosis conditions.
• Measurements included expiratory ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), arterialized venous PCO2 (PavCO2), pH (pHav), potassium (Kav+), and lactate.

Main Results:

• A ventilatory threshold was identified in both control and experimental trials, associated with isocapnic buffering.
• In control trials, Kav+ showed an inflection point near the ventilatory threshold.
• During lactic acidosis, Kav+ increased linearly with VO2, and Kav+ concentrations were similar at the ventilatory threshold in both conditions.

Conclusions:

• The pattern of arterial potassium (Ka+) change does not appear to be the sole factor responsible for the ventilatory threshold.
• The non-linear response of peripheral chemoreceptors at critical Ka+ levels warrants further investigation.