Muscle mass naturally diminishes with age. "If you don't do anything to replace the lean muscle you lose, you'll increase the percentage of fat in your body," says Edward Laskowski, M.D., a physical medicine and rehabilitation specialist at Mayo Clinic, Rochester, Minn., and co-director of the Mayo Clinic Sports Medicine Center. "But strength training can help you preserve and enhance your muscle mass — at any age."
I LOVE strength training for one simple reason right now; muscle burns fat. The more muscle you build, the more fat you burn. Get in your zone with cardio and keep it there with strength training and you'll burn more fat and increase muscle mass. I don't mean you'll bulk up like the Hulk, but you'll add a little definition where you didn't have it before. There's nothing wrong with defined legs, arms, back and abs and nobody drools more over something than a well defined butt!
Where can I start?
Small amounts of weight, resistance bands and yoga, pilates are all forms of strength training. Use lots of repetitions and repeat in sets of 3. It will defiantly help you get the definition you've been wanting. P90X uses a lot of strength training workouts. I've been doing P90X for almost 6 weeks now and I've seen huge results!
If you're looking to add bulk, take your max weight -10% and you'll get what you should be doing to add bulk in smaller repetitions.
2-3 times a week is optimal. After 3 days of not using muscles, you'll start losing them. So, you want to keep your muscles active and keep targeting the ones you want to define. However, you want to give your body a day of rest and recovery between strength training workouts.