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Consult your pediatrician. Do strength training. Start with low weights and move to heavier weights as your body gets stronger. Avoid powerlifting or competitive weightlifting. Add aerobic exercises to your weekly routine. Know the risks. Avoid too much exercise.
Before your child or adolescent participates in any form of strength training it’s important they consult their doctor. Muscle building routines are slightly different for this age group as their body is still developing and growing. Too much and too hard exercises can cause injury that have lasting effects to a young body. Receiving a medical evaluation beforehand, can help you and your child identify:  Training goals. Understanding the proper techniques. Risk factors, such as injuries and the use of steroids or other supplements. Please note that since the overall goal of strength training is to enhance muscle size, a discussion with a pediatrician about steroid use is highly important, especially if your child is involved in a competitive training program. This type of training mainly focuses on weight lifting but exercises using your own body weight (such as sit-ups and push-ups) as well as endurance and agility exercises can also be included to increase muscle strength and size.  Weight lifting is the most common strength training technique used in sports and basic workouts. To get started, consult a fitness trainer who can help you or your child learn each exercise and how to perform it correctly. Always warm up to reduce risk of injury by doing at least 5 to 10 minutes of cardio. Stretch lightly before each exercise and after the workout to increase muscle flexibility. Using weights that are too heavy can lead to an injury. Also, it is essential you learn to do each exercise correctly before adding extra weight.   Maintain your body mechanics during each move: move slowly, breathe, and understand the complete range of motion. If you do exercises hastily or using the wrong range of motion, you can risk injury. Listen to your body. The intensity of your workout depends on the number of repetitions, the weight, and how long you rest before sets. Don’t over exert yourself. However, you should still be pushing yourself. If you don't challenge your muscles and start moving on to heavier weights, your muscles will not grow or develop. Teens and children should not engage in competitive weightlifting, powerlifting or bodybuilding. These are highly demanding types of muscle building that are not suitable for children and come with a high risk of injury.  Consult with your doctor if you are unsure what type of weightlifting or strength training you or your child should do. The bodies of teens and children are still developing and growing, which greatly increases risk of injury. Aerobic exercise (or cardio) is a physical activity that raises your heart rate and engages your respiratory system. Regular aerobic exercise has many health benefits, such as maintaining body weight, reducing stress, strengthening your cardiorespiratory system, reducing risk of chronic illnesses (diabetes, cancer), and releasing endorphins to boost your mood.  Aerobic exercises that consist of weight-bearing exercises, such as walking, dancing, tennis, and running, also help strengthen your bone mass.  Adding aerobic exercises to your weekly routine, helps balance your strength-training workouts and gives a better foundation for later in life. Any type of physical activity has risks, and this is especially true for strength training. According to the National Electronic Injury Surveillance System, 20,000 to 26,000 strength-training related injuries occurred in people under 21 years old; 40 to 70 percent of those injuries were due to muscle strain, mostly in the lumbar back. Strength-training programs should be well planned and executed to reduce risk of injury. This can be accomplished by:  Having a spotter or supervision when weight lifting. Understanding the instructions of the workout so injury doesn’t occur. Understanding the use of the machine. Clearing the workout space so it is hazard free. Including proper warm-up and cool-down exercises. Working out excessively can harm your body and lead to catabolic state (breakdown of muscle protein). During the teenage years, the body is still developing and therefore, overdoing strength training or burning too many calories can cause your growing body to malfunction.  Training should only last one hour or less and you should take a rest day (or two) in between workouts so your muscles can rebuild themselves. Signs to watch to spot overtraining include: high resting heart rate, sleep difficulties, and exhaustion. If you or your child experiences any of these symptoms, cut back on the time or intensity of your workout and consult a doctor. Note to parents: too much exercise can also be a sign of an eating disorder. If you think your child is compulsively working out look for these symptoms: being upset because they missed a workout, exercising even when they’re under the weather, being upset when sitting down because they are not burning calories, and thinking that they will gain weight from going a day without exercise.