When to expect results

You don't need to spend hours a day lifting weights to benefit from strength training. You may notice stronger muscles if you do strength training at least two times a week for only about 20 to 30 minutes each time.

For most healthy adults, the Department of Health and Human Services recommends these exercise guidelines:

• Aerobic activity. Get at least 150 minutes of moderate aerobic activity a week. Or get at least 75 minutes of vigorous aerobic activity a week. You also can get an equal combination of moderate and vigorous activity. Aim to exercise most days of the week.

  For even more health benefits, the guidelines suggest getting 300 minutes or more a week of moderate aerobic activity. Exercising this much may help with weight loss or keeping off lost weight. But even small amounts of physical activity are helpful. Being active for short periods of time throughout the day can add up and have health benefits.

• Strength training. Do strength training exercises for all major muscle groups at least two times a week. One set of each exercise is enough for health and fitness benefits. Use a weight or resistance level heavy enough to tire your muscles after about 12 to 15 repetitions.

As you continue strength training, you may notice improvement in your strength and physical function over time. As your muscle mass increases, you'll likely be able to lift weight more easily and for longer periods of time. If you stick with it, you can continue to increase your strength, no matter where you started.