When you are becoming aged you lose about three pounds of muscle per decade. This creates a chain reaction that can leave you sick, weak, and physically incompetent. You may not notice that you're losing muscle, because your body replaces it with fat. And you tend to forget how much you used to have. But it's important to monitor.

Here's just a partial list of what muscle does for you:

°    Supports your bones and protects you from osteoporosis
°    Reduces your risk of osteoarthritis
°    Aids in sexual health
°    Promotes thyroid hormone production
°    Maintains adrenal production
°    Controls your metabolic rate
°    Stimulates the production of human growth hormone
°    Prevents chronic aches (like back pain)
°    Returns blood to the lungs for oxygenation

Much of the fatigue and lack of energy you may feel during the day can be eliminated by working to build new muscle. And it's not as hard as it sounds. You don't have to lift weights. Calisthenics produces remarkable results. But to build muscle, you have to focus your efforts where the muscle is.

Since the biggest muscles in your body are in your thighs, here's one of my favorite muscle-building exercises: alternating lunges. With your hands on your hips, take a step forward with your right leg until your front knee is bent 90 degrees and your back knee almost touches the ground. Push off from your leading foot and return to the starting position. Repeat with your left leg.

This exercise will build strong legs and a strong back. It will even increase your lung capacity. (And as I told you Thursday, there's a strong link between lung capacity and longevity.) Try doing 10 alternating lunges in the morning when you get up. Rest a minute and do it again.