As you age strength training is the best thing you can do to improve your health and fitness level. Strength training is important because around age 40 you start to experience muscle loss. “If you don’t do anything to replace the lean muscle you lose, you’ll increase the percentage of fat in your body,” says Dr. Edward Laskowski, a physical medicine and rehabilitation specialist at the Mayo Clinic in Rochester, Minnesota. Left unabated, you can lose up to 10 pounds of muscle each decade starting at age 40.
Losing muscle is detrimental to your fitness because muscle is the component of your body that burns the majority of the calories you consume each day. Therefore, when you lose muscle your body requires fewer calories to function. Consequently, those extra calories you consume are stored as fat around your waist, hips, and other places.
Your body constantly burns calories, even when doing nothing. This resting metabolic rate is much higher in people with more muscle. Every pound of muscle uses about six calories a day to sustain itself, while each pound of fat burns only two calories daily. This small difference can add up over time. In addition, after a bout of resistance training, muscles are activated all over your body, increasing your average daily metabolic rate.
Increasing your metabolism isn’t the only benefit of strength training. It also helps: 
· Develop strong bones. By stressing your bones, strength training increases bone density and reduces the risk of osteoporosis.
· Control your weight. As you gain muscle, your body burns calories more efficiently which can result in weight loss. The more toned your muscles, the easier it is to control your weight.
· Reduce your risk of injury. Building muscle protects your joints from injury. It also helps maintain flexibility and balance which are crucial to remaining independent as you age.
· Boost your stamina. Building muscle helps to increase your energy level while improving your sense of well-being. Strength training can boost self-confidence, improve body image, and reduce the risk of depression.
· Sleep better. People who strength train on a regular basis are less likely to have insomnia.
· Manage chronic conditions. Strength training can reduce the signs and symptoms of many chronic conditions, including arthritis, back pain, depression, diabetes, obesity, and osteoporosis.
A good strength training program should consist of exercises that target all the major muscle groups and should be performed two to four times each week. I suggest you have a certified fitness profession design a customized program for you.