Maximal lactic capacity at altitude: effect of bicarbonate loading

Area of Science:

• Exercise Physiology
• Altitude Physiology
• Sports Science

Background:

• Chronic hypoxia at high altitude affects physiological responses to exercise.
• Bicarbonate stores play a role in buffering metabolic acidosis during intense exercise.

Purpose of the Study:

• To investigate if reduced bicarbonate stores limit maximal blood lactate accumulation ([La]max) during heavy exercise in lowlanders acclimatized to chronic hypoxia.
• To test the effect of oral sodium bicarbonate loading on exercise performance and acid-base balance at sea level and high altitude.

Main Methods:

• Six lowlanders performed supramaximal exercise to exhaustion at sea level and 5,050 m.
• Exercise was conducted with and without oral sodium bicarbonate loading (0.3 g/kg body wt).
• Measurements included exhaustion time, arterial blood lactate ([La]max), arterial pH (pHa), and PCO2.

Main Results:

• At sea level, sodium bicarbonate increased exhaustion time and [La]max, and elevated resting and postexercise pHa.
• At high altitude, sodium bicarbonate did not significantly alter exhaustion time or [La]max, despite increasing resting and postexercise pHa.
• Postexercise pHa was significantly higher with bicarbonate at altitude compared to normoxia.

Conclusions:

• Reduced bicarbonate stores may limit maximal blood lactate accumulation during heavy exercise in acclimatized lowlanders at high altitude.
• Sodium bicarbonate supplementation can enhance exercise performance and lactate accumulation at sea level but not at high altitude.
• The buffering capacity of bicarbonate may be less effective or limited by other factors in the hypoxic environment.