Summary of known sex differences in pulmonary system morphology and their impact on the pulmonary physiology of exercise

Key references
Morphological differences • Males above the age of ∼14 years have proportionally greater airway luminal area of the large conducting airway (i.e., trachea to the third generation) than females[15, 1720]
• Males have larger absolute lung volumes and more alveoli than females[9, 21]
• Females have “prismatic” geometry of the ribcage and lung while males have “pyramidal” ribcage and lung geometry[2224]
Functional differences
• Higher Wb and V̇O2RM for a given absolute V̇E during exercise in females compared to males[10, 13, 5327]
  Due to a higher resistive component of Wb[25, 2830]
• Females have greater activation of “extra-diaphragmatic” inspiratory muscles for a relative or absolute V̇E during exercise
Noted in the scalene and sternocleidomastoid muscles
[31, 32]
• Highly trained males are less likely to develop expiratory flow limitation during exercise than highly trained females[13, 25]
• Females have a blunted respiratory muscle metaboreflex[3337]
• EIAH can occur in untrained females but does not appear to occur in untrained males[3840]
• Older females have a higher perception of dyspnoea at absolute and relative exercise intensities than older males[10, 11, 41]

EIAH: exercise-induced arterial hypoxaemia; V̇E: minute ventilation; V̇O2RM: oxygen uptake of the respiratory muscles; Wb: work of breathing.