According to a researcher at the University of Michigan, a program of good exercise may help a person fight off colds and infection. The theory is that a good workout puts the body in a condition similar to what happens at the onset of a fever. That's not all bad. Most biologists are of the opinion that a fever is the body's way of fighting back when micro-intruders get into the system. Increased body temperature seems to aid the white-cell defense system while slowing down the action of bacteria and viruses. Exercise, it is now thought, does the same thing. It releases chemicals into the blood that stimulate the brain to make our temperature rise.
The Bible teaches that a regular course of good spiritual exercise is highly beneficial to the health of our soul. It shows us that sin is effectively warded off in a person who is walking in the light, one who is obeying Jesus each day. On the other hand, disobedience or following the path of least resistance cools down a person's spiritual temperature. Fellowship is neglected. Sin is neither confessed nor forsaken. The result is a lukewarm or cold Christian who is not taking advantage of the kind of defenses necessary to fight spiritual infection where it exists.