Physical training and connective tissues in young mice-heart.

The effect of physical training on the chemical properties of the heart tissues was studied in male mice of NMRI-strain. The mice to be trained and their controls were about 2 weeks old at the beginning of the training, which took place on 5 degrees inclined treadmill 5 days a week for 3-22 weeks. The duration of daily exercise was progressively increased over the first 3 weeks. The final daily exercise bouts were 50 and 80 min for moderate programs and 180 min for the intensive program at a speed of 30 cm/s. The whole heart or the ventricles were used for the analyses. We found no significant changes related to training in the concentrations of nitrogen, hexosamines, and hydroxyproline both in the normal-sized and the hypertrophied hearts. The hydroxyproline concentration of the ventricles was lower than that of the whole heart tissue, but no difference was observed in the concentration of nitrogen. The hydroxyproline concentration of the heart tissue increased with age both in the trained and untrained mice (39% over 19 weeks). We conclude that collagen and non-collagen proteins in the heart tissue of young mice are stimulated in equal proportions by physical training.