Philip J. Goscienski, M.D.
Just before our high school graduation a classmate broke his leg in a bicycle accident. He was still a little wobbly when the cast came off six weeks later. No wonder. The leg that had been under a cast obviously had shrunk compared to its partner. Anyone who has experienced a broken arm or leg has had the same experience: an immobilized body part, having nothing to do, simply begins to waste away.
What happens under a cast in six weeks happens to most people during a lifetime of 60 or 70 years. A cartoon-like character in a current TV ad makes the point: adults lose one-half to one percent of their muscle mass every year. It has nothing to do with aging and taking a protein-rich supplement won't help without a moderate amount of physical activity.
Something else happens under a cast that is left on for 6 weeks but it's not apparent to the naked eye. It might not even be seen on x-ray but there is a significant amount of bone loss. Until a bone has lost about 25 percent of its mass an ordinary x-ray won't reveal much, which is why an x-ray is a poor screening method for osteoporosis.
And that's not all. My classmate's wobbly gait was partly due to the loss of nerve endings on the wasted muscle fibers. These spindle cells help the body to maintain balance by providing position sense. This is the same system that allows you to close your eyes and unerringly touch the tip of your nose. (Most people will try this before they read any further!)
After a cast has been removed a normally active teenager will rebuild the lost muscle and bone quickly. Everyone needs to remain active enough to keep muscles and bones from wasting away over decades. A brisk walk several days a week and two or three days of resistance exercise, each lasting about an hour, ought to be enough. A couple of hours of yard work or gardening, tennis, nine holes of golf (pulling a cart, not riding in one!), square dancing, biking, bowling or similar activities are gym substitutes that help to preserve muscle and bone. Pool exercises that utilize resistance are good but swimming, which is great for the heart and lungs, is not a bone-building exercise.
If you never broke a bone during childhood, be sure to stay active so that you can avoid it now.
Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at firstname.lastname@example.org.