The following is a  post from Lou Schuler, an award-winning journalist and certified strength and conditioning specialist. 

1. The older you are, the more important it is to lift
Research at McMaster University has shown that strength training can reverse the signs of aging at the cellular level by as much as 20 percent. But that knowledge doesn’t do you any good unless you actually get into the weight room and improve the size and strength of your muscles.

2. No matter your age, the goal of strength training is to train something
Middle-aged lifters have a tendency to go through the motions. If you want your body to look or perform better, you have to train it to do more than it can do now. You need to increase the weights you lift, and the number of times you lift them, in a steady, systematic way. If you want to be leaner, you have to train your body to use more calories during your workouts. That means working harder and getting more accomplished from one week to the next.

3. “Working harder” doesn’t mean beating yourself up every time
Training is a process of imposing stress on your body in calculated doses. Too little stress and you get disappointing results. Too much and you don’t recover sufficiently from one workout to the next. It only works if you can train just as hard on Wednesday as you did on Monday, and at least as hard on Friday as you did on Wednesday. It’s not like planting a garden, where it doesn’t matter how sore you get after a day of digging because you have all summer to recuperate.

4. Kids are stupid. Don’t train like one
The average young person has a profoundly unrealistic view of how the human body works. But so does the middle-aged guy with a 40-inch waist who sits on a bench working his biceps and triceps, when his arms would look 100 percent better if his belly were 20 percent smaller.

No matter your age, you get the most benefit from the exercises that work the most muscle in coordinated action, and do the most to improve total-body strength. Those exercises–squats, deadlifts, chin-ups, presses and rows–also burn the most calories, both during and after exercise, while you’re recovering.

5. Heavy weights won’t make you huge, but they can make you lean
Males don’t have the market cornered on unrealistic expectations. The woman doing presses and rows with dumbbells smaller than her forearms is trying to do the impossible: “tone” muscles she hasn’t yet built. She’s worried about getting “too big,” which is equally absurd. Muscle is hard to build at any age, for either gender, and it never happens by accident.

The good news is that the muscle-building process creates a stronger, leaner, healthier, and better-conditioned body even when the actual increase in muscle tissue is minimal. But it only works if you try to build muscle by using weights that are pretty close to the heaviest you can lift.

If the workout tells you to do 10 repetitions, for example, you need to pick a weight that you could lift, at most, 11 or 12 times. Studies show that adults typically choose weights that are much lighter than the workout calls for.

6. Muscle needs to be fed
The older you get, the more resistant your muscles are to protein. So you need a bit more to ensure you don’t lose them before you’re done using them. Government recommendations are useless. They call for 10 to 35 percent of your daily calories from protein. So on a 2,000-calorie diet, that’s between 50 and 175 grams a day. Thanks Government!

A better standard for an adult lifter, courtesy of nutritionist Alan Aragon: Shoot for at least 1 gram of protein for every pound of your target body weight. If you weigh 140 pounds now and you hope to drop 20 pounds, you want at least 120 protein grams a day. Since a gram of protein is 4 calories, 120 grams would be a third of your nutrition on a 1,500-calorie-a-day diet, or a quarter of a 2,000-calorie diet.

7. A perfect workout should include five basic movement patterns.
The less you focus on exercises for specific muscles, and the more you focus on movement patterns that use lots of muscles, the better your body will look, feel, and perform.