Engines of the Body
The automatic transmission in a vehicle changes gears in response to changing power demands and driving conditions. Likewise, the muscles in your body change gears in a sense, in response to your changing needs for them.
When you use a muscle group, the muscles begin to need more fuel and more oxygen, both brought to them by your blood. When you use a set of muscles, lots of new blood vessels will actually grow into the tissue to meet the increasing demand. This is one way in which exercise lowers blood pressure – by increasing the “tubing” through which it passes. If you often overuse a group of muscles, additional connective tissue will grow through the muscles, strengthening them.
The “automatic transmission” in your muscles engages when you use the same group of muscles for a continuing task like rowing a boat. Before long, the normal fuel freely available in your blood is used up. At that point your body mobilizes stored fat, which allows the muscles to continue without exhaustion. Muscles that are often used to this point actually become more efficient at burning fat reserves. In even more strenuous exercise, a third “gear” kicks in, changing the way muscles burn fuel, so there is less waste for the circulatory system to deal with.
As scientists learn more about our incredibly complex and intelligently designed bodies, we find even more reasons to bear witness to our wonderful and wise Creator.