Getting started

If you have a chronic condition, or if you're older than age 40 and you haven't been active recently, check with your doctor before beginning a strength training or aerobic fitness program.

Before beginning strength training, consider warming up with brisk walking or another aerobic activity for five or 10 minutes. Cold muscles are more prone to injury than are warm muscles.

Choose a weight or resistance level heavy enough to tire your muscles after about 12 to 15 repetitions. When you can easily do more repetitions of a certain exercise, gradually increase the weight or resistance.

Research shows that a single set of 12 to 15 repetitions with the proper weight can build muscle efficiently in most people and can be as effective as three sets of the same exercise. As long as you take the muscle you are working to fatigue — meaning you can't lift another repetition — you are doing the work necessary to make the muscle stronger. And fatiguing at a higher number of repetitions means you likely are using a lighter weight, which will make it easier for you to control and maintain correct form.

To give your muscles time to recover, rest one full day between exercising each specific muscle group.

Also be careful to listen to your body. If a strength training exercise causes pain, stop the exercise. Consider trying a lower weight or trying it again in a few days.

It's important to use proper technique in strength training to avoid injuries. If you're new to strength training, work with a trainer or other fitness specialist to learn correct form and technique. Remember to breathe as you strength train.