Getting started

When you have your doctor's OK to begin a strength training program, choose a weight or resistance level heavy enough to tire your muscles after about 12 repetitions. When you can easily do more repetitions of a certain exercise, gradually increase the weight or resistance.

"On the 12th repetition, you should be just barely able to finish the motion," Dr. Laskowski says. "When you're using the proper weight or amount of resistance, you can build and tone muscle just as efficiently with a single set of 12 repetitions as you can with more sets of the same exercise."

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. Although mild muscle soreness is normal, sharp pain and sore or swollen joints are signs that you've overdone it.

When to expect results

You don't need to spend hours a day lifting weights to benefit from strength training. "Two to three strength training sessions a week lasting just 20 to 30 minutes are sufficient for most people," Dr. Laskowski says.

Better yet, results are quick. Expect to enjoy noticeable improvements in your strength and stamina in just a few weeks. If you keep it up, you'll continue to increase your strength — even if you're not in shape when you begin.

Apr. 24, 2013 See more In-depth

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