Swimmers' Lungs are not Like Other Humans'


Lung illustration.By Dan McCarthy//High Performance Consultant

Conventional wisdom says that lung capacity cannot be increased. There are mechanisms for athletes to increase how efficiently they use the oxygen they inspire, but increasing the actual capacity of the lungs is considered to be a dodgy proposition.


But, wait a minute!


There is credible research that suggests swimmers, in particular, have overcome normal human biology and significantly increased their lung capacity. How can this be?


Swim training, like other forms of physical activity, results in some basic changes in human physiology, which increases how efficiently the human body uses oxygen. Primarily, at the cellular level the size and number of Mitochondria1 increase with high-intensity endurance training. The adaptations related to using oxygen more efficiently are:

  • An increase in respiratory enzymes
  • An increase in the muscles ability to extract more oxygen from the blood
  • An increase in the muscles ability to use free fatty acids to fuel activity

None of the most common textbooks mention anything about increasing an athlete’s lung capacity. However, at least three studies found increases in total lung capacity for swimmers who engaged in intensive swim training programs. How? The apparent answer is very basic, but makes total sense.


Intensive swim training, not running or cycling, seems to result in humans developing wider chests. The increased chest size results in a larger number of alveoli in the lungs. The alveoli in the lungs exchange oxygen with the circulating red blood cells. The more alveoli, the more oxygen which can be exchanged and sped to the athlete’s working muscles. One of the end results, of course, is increased lung capacity.

Articles Referenced
Armour, J., Donnelly, P., & Bye, P. (1993). The large lungs of elite swimmers: an increased alveolar number? The European Respiratory Journal, 237-247.


Courteix, D., Obert, P., Lecoq, A., Guenon, P., & Koch, G. (1997). Effect of intensive swimming training on lung volumes, airway resistance and on the maximal expiratory flow-volume relationship in prepubertal girls. European Journal of Applied Physiology, 264-269.


Mickleborough, T., Stager, J., Chatham, K., Lindley, M., & Ionescu, A. (2008). Pulmonary adaptations to swim and inspiratory muscle training. European Journal of Applied Physiology, 635-646. 


1 Mitochondria are the engines of the cells; they convert energy into fuel for the cell to use