Training effects on the regional blood flow response to exercise in myocardial infarcted rats

The regional blood flow (BF) response to submaximal exercise was determined for sedentary and trained myocardial infarcted (MI) rats. Training consisted of treadmill running (10% grade, 30 m/min) for 1 h/day, 5 days/wk for 12-14 wk and produced decreases in resting heart rate and increases in maximal O2 uptake and endurance capacity. BF determined at 2 and 6 min of exercise (via radiolabeled microspheres) demonstrated that trained rats maintained greater BF to organs found in the abdominal region when compared with their sedentary counterparts. BF to the total hindlimb musculature at 2 min of exercise was greater in sedentary rats when compared with their trained counterparts and was the consequence of greater BF to 10 of the 27 muscle or muscle parts investigated. At 6 min of exercise, BF to the total hindlimb musculature was similar between trained and sedentary rats, as BF in 9 of 27 muscles or muscle parts investigated decreased from 2 to 6 min of exercise for the sedentary group. In general, the BF patterns within and among the individual muscles of the hindlimb were different between the two groups. Trained rats tended to maintain greater BF to the predominantly red muscles, whereas the sedentary rats maintained greater BF to the predominantly white muscles at 6 min of exercise. In conclusion, the training-induced changes in BF found in this study are similar to those found previously for normal rats, and they demonstrate that endurance training produces changes in the regional distribution of BF during exercise in MI rats.