Lung function is known to change with immersion and body position. However, little is known about these changes in endurance athletes, particularly regarding the influence of allergies and asthma in this population. This study aims to clarify related changes in trained endurance athletes’ lung function associated to different body positions and immersion, and allergies and asthma influence on those changes.

Athletes underwent spirometry testing at rest in four randomized positions: seated on land, prone on land, seated while immersed, and prone while immersed. The sample was comprised of 45 male athletes: 15 swimmers, 15 triathletes, and 15 runners. Data from the spirometry tests were collected in a pool and pool's deck.

All the lung function variables varied across the different positions (FVC, FEV ₁ , and FEF _25-75% with p  <  0.001, and PEF with p = 0.001), except for FEV ₁ /FVC, which remained unchanged (p = 0.207). Overall, athletes without self-reported allergies or asthma showed greater positional differences.

Endurance athlete's FVC, FEV ₁ , and FEF _25-75% appear to decrease primarily in response to hydrostatic pressure, while PEF decreases mainly in response to the change in body position. FVC in allergic athletes, and FEV ₁ , and FEF _25-75% in asthmatic athletes appear to decrease mainly in response to the change in body position, and PEF decreases mainly in response to hydrostatic pressure. The specific effects in response to allergy and asthma appear to accumulate with the overall effects, leading to differences from the on-land seated condition to the other three positions, but no difference among the later three positions.