Increased steady-state VO2 and larger O2 deficit with CO2 inhalation during exercise

Area of Science:

• Exercise Physiology
• Respiratory Physiology
• Metabolic Studies

Background:

• Understanding the physiological responses to altered respiratory gas mixtures is crucial for exercise science.
• Carbon dioxide (CO2) inhalation can induce respiratory acidosis, potentially affecting metabolic and cardiorespiratory functions during physical activity.

Purpose of the Study:

• To determine if inhaling CO2-enriched gas increases steady-state oxygen consumption (VO2) during exercise.
• To investigate whether CO2 inhalation enlarges the oxygen deficit during exercise.

Main Methods:

• Ten physically active men performed cycling exercise at light and heavy intensities.
• Participants inhaled either normal air or a CO2-enriched gas mixture (4.2% CO2).
• Gas exchange was measured using the Douglas bag technique to assess VO2 and other metabolic parameters.

Main Results:

• Inhalation of CO2-enriched air induced respiratory acidosis, increasing PCO2 and decreasing blood pH.
• Steady-state VO2 was approximately 6% higher with CO2 inhalation during both light and heavy exercise.
• The oxygen deficit was significantly greater during heavy exercise with CO2 inhalation compared to normal air.

Conclusions:

• Inhaling CO2-enriched air increases steady-state VO2 during both light and heavy exercise.
• CO2 inhalation, leading to respiratory acidosis, enlarges the oxygen deficit specifically during heavy exercise.