The large lungs of elite swimmers: an increased alveolar number?

Abstract

In order to obtain further insight into the mechanisms relating to the large lung volumes of swimmers, tests of mechanical lung function, including lung distensibility (K) and elastic recoil, pulmonary diffusion capacity, and respiratory mouth pressures, together with anthropometric data (height, weight, body surface area, chest width, depth and surface area), were compared in eight elite male swimmers, eight elite male long distance athletes and eight control subjects. The differences in training profiles of each group were also examined. There was no significant difference in height between the subjects, but the swimmers were younger than both the runners and controls, and both the swimmers and controls were heavier than the runners. Of all the training variables, only the mean total distance in kilometers covered per week was significantly greater in the runners. Whether based on: (a) adolescent predicted values; or (b) adult male predicted values, swimmers had significantly increased total lung capacity ((a) 145 +/- 22%, (mean +/- SD) (b) 128 +/- 15%); vital capacity ((a) 146 +/- 24%, (b) 124 +/- 15%); and inspiratory capacity ((a) 155 +/- 33%, (b) 138 +/- 29%), but this was not found in the other two groups. Swimmers also had the largest chest surface area and chest width. Forced expiratory volume in one second (FEV1) was largest in the swimmers ((b) 122 +/- 17%) and FEV1 as a percentage of forced vital capacity (FEV1/FVC)% was similar for the three groups. Pulmonary diffusing capacity (DLCO) was also highest in the swimmers (117 +/- 18%). All of the other indices of lung function, including pulmonary distensibility (K), elastic recoil and diffusion coefficient (KCO), were similar. These findings suggest that swimmers may have achieved greater lung volumes than either runners or control subjects, not because of greater inspiratory muscle strength, or differences in height, fat free mass, alveolar distensibility, age at start of training or sternal length or chest depth, but by developing physically wider chests, containing an increased number of alveoli, rather than alveoli of increased size. However, in this cross-sectional study, hereditary factors cannot be ruled out, although we believe them to be less likely.

Respiratory parameters in elite athletes – does sport have an influence?

“…Higher values of forced vital capacity were registered in basketball, water polo and rowers compared to controls. It contrasts with previous reports which found that all athletes, regardless of the sport, had higher lung volumes than physically inactive persons 3,4,6,9,10 . Our study showed that the researched respiratory parameters in athletes had approximately the same value of lung volumes as the control group, except for above mentioned groups.…”

“…2 Lung volume is fairly well predicted on the basis of age, height and weight, but lung volumes which are larger than predicted have been repeatedly observed in athletes compared to their control counterparts who are not engaged in any kind of regular physical exercise. 3,4 There are some physiological explanations as to why athletes have higher lung volumes, but still, this is an uncharted field. 5 Studies about athletes' respiratory functions are rather limited or have been tested on too small number of participants, mostly related to individual sports.…”

Determinants of lung function changes in athletic swimmers. A review

“…In 9-10 years old, only inspiratory force (FImax) was significantly higher compared to controls, 29 whereas in older swimmers and runners, forces were not different between the groups. 11 Even if there might be a possible training effect on inspiratory muscle force, the lack of increased inspiratory flows in swimmers weakens the significance of this finding. 28 With the available evidence, the hypothesis that supranormal lung volumes in swimmers directly related to increased respiratory muscle strength and pressures cannot be confirmed.…”

“…16 Lastly, a study comparing competitive swimmers to long distance runners and non-athletic controls found no difference in P I max and P E max among groups despite the observation that all lung volumes were greater in swimmers. 11 Again, these data go against the assumption that increased lung volumes in swimmers are due to an increased ability to inflate and deflate the lungs in relation to changes in inspiratory/expiratory pressures.…”

“…31,33 Similar mechanical stress may occur following repetitive inspiration to TLC during swim training, ensuing enhanced expression of growth factors such as vascular, epithelial or hepatocyte growth factors (VEGF, EGF and HGF). In this regard, Armour et al 11 previously suggested that swimmers may develop greater lung volumes than other athletes or non-athletes by developing physically wider chests, containing an increased number of alveoli, rather than an increase in alveolar distensibility or size. Wider chest and higher bi-acromial breadth for age has also been measured by others.…”