Strength training is an important part of a balanced exercise routine that includes aerobic activity and flexibility exercises.  Regular aerobic exercise, such as running or using a stationary bike, makes your muscles use oxygen more efficiently while strengthening your heart and lungs. When strength training with weights, you're using your muscles to work against the extra pounds, therefore increasing the amount of muscle mass in your body by making your muscles work harder than they're used to.

Weight Lifting Terminology

Free weights. Free weights including barbells, dumbbells, and hand weights. Free weights usually work a group of muscles at the same time.

Weight machines. Weight machines are typically designed to help you isolate and work on a specific muscle.

Strength training. Strength training uses resistance methods like free weights, weight machines, resistance bands, or a person's own weight to build muscles and strength.

Powerlifting. Powerlifting concentrates on how much weight a person can lift at one time.

Getting Started
Any time you start a new sport or activity, start out slowly so that your body gets used to the increase in activity. Even if you think you're not exerting yourself very much, your muscles may be sore the next day. And, because of something called delayed onset muscle soreness, the pain may be at its worst 2 or 3 days after you first exercise.

Before you begin any type of strength training routine, get some guidance and expert advice. Your coach or trainer can give you advice on how many times a week you should lift and what kinds of warm-up and cool-down activities you should do before and after lifting to avoid soreness or injury. 

What Are Some Dangers of Strength Training?
You may love the challenge of lifting, especially if you and your friends do it together. You'll definitely see results over a few months in your ability to progressively lift more weight, but there are a few things to look out for.

Damaging bones, joints and tendons. Your bones, joints, and tendons are still growing and developing, it's easy to overdo it and strain or even permanently damage them.

Performance Enhancing Drugs. Anabolic steroids or other performance-enhancing drugs and preparations that supposedly help muscles develop. Steroid use is widespread in many sports, but because many of their long-term effects on the body are still unknown (and because they are linked to health problems like cancer, heart disease, and sterility), resist the urge to try them. The benefit is definitely not worth the risk!

Here are some basic rules to follow in strength training:

1. Start with body weight exercises for a few weeks (such as sit-ups, pushups, and pull-ups) before using weights.
2. Work out with weights about three times a week and avoid weight training on back-to-back days.
3. Warm up for 5-10 minutes before each session.
4. Spend no more than 40 minutes in the weight room to avoid fatigue or boredom.
5. Work more reps; avoid maximum lifts.
6. Use proper technique - Improper technique may result in injuries, particularly in the shoulder and back.
7. Cool down for 5-10 minutes after each session, stretching the muscles you worked out.

Don't rely on strength training as your only form of exercise. You still need to get your heart and lungs working harder by doing some kind of additional aerobic exercise for a minimum of 20-30 minutes per session. Doctors recommend an hour a day of moderate to vigorous activity — so on days when you're not lifting weights, you may want to get more aerobic activity.

Strength training is a great way to improve strength, endurance, and muscle tone. Remember to start slowly, use proper form, avoid heavy weights, and increase workouts gradually to prevent injury. Just a few short sessions a week will really pay off — besides better muscle tone and definition, you may find that you have more energy and focus in both sports and school.