Women, Men, and Thermal Response: An Entropic Account of Gender Differences in Breathing During Exercise

Abstract

This study aimed to determine differences in the thermal response of the respiratory muscle between healthy men and women during exercise. We analyzed the lungs of eight men and eight women thermodynamically. Previous work of breathing data of 16 endurance-trained healthy subjects undergoing a progressive cycle exercise test to exhaustion was used for calculations. During exercise, glucose absorbed from the blood flow was 2.12 mmol/L for men and 4.1 mmol/L for women. Glucose consumed for respiration was found as 10.6 and 20.49 mmol/min in men and women, respectively. Exergy destruction in the respiratory muscles of men and women was 0.41 and 0.79 kJ/min, respectively. Entropy generation rates for men and women were calculated as 1.38x10-3 and 2.66x10-3 (kJ/K)/min, respectively. Women were generated entropy remarkably higher than men and consumed more glucose than men during exercise for breathing due to their less efficient ventilatory response to exercise. In conclusion, gender-based alterations in lung and airway dimensions result in higher work of breathing and therefore glucose cost of respiration, higher exergy destroyed, and higher entropy generated in women during exercise for given exercise intensity.