The effects of maternal exercise on developing rat fetuses.

Ten female Sprague-Dawley rats (45.3 days old, s.d. = 3.9) were acclimatised to running on a treadmill at 20 m/min on a 10 degrees incline for 1 hour per day. After mating, one rat from each of 5 pairs continued running on the treadmill at 15 m/min on a 10 degrees incline for 1 hour per day throughout gestation whilst the other rats followed normal laboratory routine. All the rats were weighed daily and at birth the number and weights of all fetuses were measured. In addition, a small piece of diaphragmatic muscle was taken from each of three fetuses from each litter and assessed both histologically and histochemically. The results showed that the maternal rats that did not continue exercising throughout pregnancy produced, on average, approximately 3 more fetuses per litter than the rats that exercised, although this difference was not significant. There was also no difference in mean fetal weight between the two groups and no difference could be demonstrated in the development of the diaphragm muscle.