So, the point is, that if he were to hold his pressure constant, he would be in trouble.  That is part of the problem with giving beta blockers. They leave people with difficulty in varying their blood pressure.

The other problem about homeostasis concerns the fact that the Safety factors are small to minimize excess capacity. You want things to be efficient. You don’t want to have an excess of blood. You want to minimize what you have. This is achieved by trade-offs that are regulated by our brain. So, Exercise requires an 18-fold increase in blood to muscle. The heart-lung output can increase only 3.25-fold. The brain predicts that the liver, gut, and kidney can afford less flow. They can wait awhile. The brain shunts the blood from these organs to the muscle. So, the brain makes these tradeoffs by making a temporary “loan” to the muscles. This allows a much smaller cardiovascular plant then would otherwise be possible.

Principles of Neural Design 2015