Strength training (also called resistance training) is a way to build muscles and strength using free weights, kettlebells, weight machines, resistance bands, or a person's own weight. Teens may want to strength train to improve sports performance, treat or prevent injuries, or improve appearance.

People who work out with weights can use:

• free weights, including barbells, dumbbells, and kettlebells. Free weights are portable and inexpensive, but it might take some practice to learn good technique.
• weight machines, which make it easier to follow good technique, but you may have to go to a gym or weight room to use them.

People can also use resistance bands and even their own body weight (as in push-ups, sit-ups, planks, and squats) for strength training.

If you haven't started puberty, strength training will help you get stronger but your muscles won't get bigger. After puberty, the male hormone testosterone helps build muscle in response to weight training. Because guys have more testosterone than girls do, they get bigger muscles.

What Are the Benefits of Strength Training?

Besides building stronger muscles, strength training can:

• improve overall fitness
• increase lean body mass (more muscle, less fat)
• burn more calories
• make bones stronger
• improve mental health

How Do I Get Started?

Before you start strength training, visit your doctor to make sure it's safe for you to lift weights. When you get the OK from your doctor, get some guidance and expert advice.

Coaches and trainers who work at schools, gyms, and in weight rooms know about strength training. Many schools offer weight or circuit training in their gym classes. Or check out your local gym to see if you can sign up for a strength training class or work with a personal trainer. Look for someone who is a certified strength training expert with experience working with teens.

The best way to learn proper technique is to do the exercises without any weight. After you've mastered the technique, you can gradually add weight as long as you can comfortably do the exercise for 8–12 repetitions.

When lifting weights — either free weights or on a machine — make sure that someone is nearby to supervise. Having a spotter is especially important when weightlifting. Even someone in great shape sometimes just can't make that last rep. It's no big deal if you're doing biceps curls; all you'll have to do is drop the weight onto the floor. But if you're in the middle of a bench press — a chest exercise where you're lying on a bench and pushing a loaded barbell away from your chest — it's easy to get hurt if you drop the weight. A spotter can keep you from dropping the barbell onto your chest.

Is Strength Training Safe?

Strength-training programs are generally safe. When done properly, strength training won’t hurt growing bones. Teens with some medical conditions — such as uncontrolled high blood pressure, seizures, or heart problems — will need to be cleared by their doctors before starting a strength-training program.

When you're in the middle of a strength-training session and something doesn't feel right to you, you feel pain, or if you hear or feel a "pop" during a workout, stop what you're doing. Have a doctor check it out before you go back to training. You may need to change your training or even stop lifting weights for a while to allow the injury to heal.

Many people tend to lump all types of weightlifting together. But there's a big difference between strength training, powerlifting, and bodybuilding. Powerlifting concentrates on how much weight a person can lift at one time. The goal of competitive bodybuilding is to build muscle size and definition.

Powerlifting, maximal lifts, and bodybuilding are not recommended for young people who are still growing because they can cause serious injuries.

Some people looking for big muscles may turn to anabolic steroids or other performance-enhancing drugs. These substances are risky and can cause problems like mood swings, acne, balding, and high blood pressure. They also increase a user's risk for cancer, heart disease, and sterility.

What's a Healthy Routine?

Here are some basic rules to follow in strength training:

1. Warm up with dynamic exercises for 5–10 minutes before each session.
2. If you are new to strength training, start with body weight exercises for a few weeks (such as sit-ups, push-ups, and squats) and work on your form and technique without using weights.
3. When you've learned proper technique, start with a relatively light free weight or low-resistance bands. Increase the weight, number of sets, or types of exercises gradually as your strength improves.
4. Start with 1–2 sets of 8–12 repetitions. A certified trainer, coach, or teacher can help put together a program that's right for you.
5. Learn correct technique and always train with supervision.
6. Cool down after each session with light activity and static stretching.

For best results, do strength exercises for at least 20–30 minutes 2 or 3 days per week. Take at least a day off between sessions. Work the major muscle groups of your arms, legs, and core (abdominal muscles, back, and buttocks).

Strength training is just one part of a balanced exercise routine. Experts recommend at least 1 hour a day of moderate to vigorous physical activity, including strength exercises and:

• aerobic (cardio) activity, which strengthens your heart and lungs. Walking, running, and swimming are good aerobic activities.
• stretching, which improves your flexibility

Also, drink plenty of liquids and eat a healthy diet for better performance and recovery.