Physiological responses to resistance breathing during short and prolonged exercise

Area of Science:

• Physiology
• Exercise Science
• Respiratory Medicine

Background:

• Respirators can impede breathing, potentially limiting exercise intensity.
• This limitation is critical in emergency scenarios demanding high physical exertion.
• Previous studies often focused on subjective discomfort rather than objective physiological limits.

Purpose of the Study:

• To determine the physiological limits of exercise intensity imposed by varying levels of breathing resistance.
• To investigate the impact of external breathing resistance on exercise capacity and duration.
• To establish the relationship between breathing resistance and maximal aerobic capacity (% VO2 max).

Main Methods:

• Motivated subjects performed exercise tests with external breathing resistances of 11, 16, 25, 40, and 57 cm H2O at 120 L.min-1 flow rate.
• Exercise intensity was measured as a percentage of maximum aerobic capacity (% VO2 max).
• Short-term and prolonged (1-hour) exercise durations were assessed.

Main Results:

• Exercise limits decreased with increasing breathing resistance, ranging from 79% to 54% of % VO2 max for short-term exercise.
• Prolonged exercise limits showed a more pronounced reduction, from 60% to 35% of % VO2 max with increasing resistance.
• Significant external breathing resistance altered the typical exercise intensity-duration relationship.

Conclusions:

• External breathing resistance significantly reduces exercise intensity and duration capabilities.
• Physiological limits are demonstrably affected by breathing resistance, surpassing subjective discomfort thresholds.
• Findings are crucial for understanding performance limitations in occupational and emergency settings involving respirator use.