The influence of physical exercise on growth and sexual maturation in young female rats

This investigation deals with the influence of physical activity on the growth and sexual maturation of weanling female Wistar rats. It involves three groups of rats, namely an intensively trained group (n = 45), a moderately trained group (n = 49) and a nontrained group (n = 49). The trained groups were forced to perform physical exercise from the age of 15 days on, on a treadmill. Within the intensively trained group, exercise was increased by increasing the speed and grade of the treadmill. The exercise of the moderately trained group was held constant. A delay in the day at vulva opening, indicating sexual maturation is seen in the extensively trained group in comparison with the moderately trained and nontrained group. The average body weight at the day of vulva opening is the same in all groups. However, the correlation coefficient between day at vulva opening and body fat mass is not significant. No differences in the body- and tail-length growth can be detected between the groups. A delay in the sexual maturation due to stress can be rejected since the open fields results registrating stress parameters, as obtained from the various groups of animals, are in general not significantly different between the intensively trained and moderately trained as well as nontrained groups. This investigation shows evidence that intensive physical exercise from young age on, causes a delay in sexual maturation, although it has no influence on the body- and tail length growth.