Adaptive cardiovascular changes to physical training in spontaneously hypertensive and normotensive rats

Spontaneously hypertensive rats and normotensive control rats were physically trained during 16 weeks on a treadmill. The effects on blood pressure and on left and right ventricular weight were measured, and haemodynamic analyses were performed to explore whether the resistance vessels of the hindquarter muscles had been affected in their design characteristics. The training period did not affect ‘resting’ blood pressure levels in either of the groups. Left ventricular weight was increased in trained normotensive control rats, but not in trained spontaneously hypertensive rats compared with untrained controls. Right ventricular weight was, on the other hand, increased in both trained groups but to a grearer extent in spontaneously hypertensive rats than in normotensive control rats. Resistance to flow in the maximally dilated hindquarter vascular bed was decreased in both trained spontaneously hypertensive rats and normotensive control rats although somewhat less in the spontaneously hypertensive rats compared with untrained controls. It was concluded that the vascular bed of skeletal muscle is able to adjust to the increased flow demands caused by regular physical work by a structurally based widening of the resistance vessels in both hypertensive and normotensive animals. However, this adjustment to local flow demands is associated with a maintenance of the wall/lumen ratios characteristic of normotensive and hypertensive resistance vessels as governed by the average pressure load.