Effects of exercising rats during pregnancy.

To determine the effects of exercise during pregnancy on the cardiovascular system of their progeny, female Sprague-Dawley rats were assigned to one of four groups: 1) trained-nontrained (T-NT) animals who ran for 7 wk at 35 m/min before but not during pregnancy; 2) T-T animals who ran at 35 m/min before and at 32 m/min during pregnancy; 3) control (C) animals who did not exercise; and 4) NT-T animals who only ran (16 m/min) during pregnancy. Significant increases in skeletal muscle cytochrome found between exercised (NT-T, T-T) and nonexercised (C, T-NT) mothers; C animals had significantly lower maximal oxygen consumption (VO2max) values than T-T animals at the end of pregnancy. Offspring mortality was greater (P less than 0.05) in the T-T compared with the C group during the 28 days following birth. Maternal exercise had no significant influence on VO2max in the offspring or on myocardial blood flow when these animals were ventilated with either hypoxic (10% O2) or normoxic (21% O2) gases. Right ventricular fiber areas were smaller (P less than 0.05) in T-T and NT-T animals compared with the T-NT group; no significant changes were observed in the left ventricle. Capillary density and fiber-to-capillary ratios were not different in either the right or left ventricle. These results indicate that mild or heavy exercise does not influence VO2max, coronary blood flow in response to stress, or myocardial structure in the male offspring of rats trained during pregnancy.