The effects of physical training on the lung growth of infant rats

The effect of swimming exercise on the growth of the lungs was examined in 60 Charles River Outbred Albino male rats during their second and third months of life. A tw0-by-three factorial analysis of variance design was used for significant differences due to duration of exercise (swimming 5 minutes per day 5 days per week, swimming to exhaustion 5 days per week, and no exercise) and duration of training (4 weeks and 8 weeks). All rats were loaded equal to 5 percent of body weight while swimming. Measurements used to evaluate lung growth were lung blood volume, lung blood volume/body weight, alveolar density, ratio of alveolar surface area to respiratory volume, lung weight, and lung weight/body weight. It was concluded that alveolar proliferation was increased in rats exposed to swimming during the second month of postnatal growth as indicated by greater alveolar densities and surface area to respiratory volume ratios is exercised subjects. Failure to find further growth during the third month of life suggested a critical period prior to the third month for such proliferation. Nonexhaustive swimming was as effective as exhaustive swimming in promoting the proliferation. There was no interaction between duration of exercise and duration of training.