A big misconception in the fitness world is that strength training can stunt the growth of children and that they should not lift weights until they are 12 years of age. According to the American Council on Exercise (which I have been certified through my entire career) ,there is no research to support this claim. Research actually shows many benefits for youth that weight train. All the major fitness and medical organizations recommend strength training for our youth.
Strength training with weights is suitable and safe as long as the child can follow directions and keep proper form. Even at the age of 7 or 8 years old weight training can be a beneficial in many ways. Teaching them safe and proper form and making sure there is an adult present that has had experience or training to assist them is paramount. I have taught many kids how to lift weights properly. I love to watch how they take it with them into adulthood.
The benefits of youth strength training include muscular fitness, bone density, better body composition, injury resistance, better sports performance and improved self esteem.
Kids that learn how to train with weights when they are young will most likely make better lifelong fitness decisions.
That said, kids need to have fun with exercise. Even though weight training needs to be taken seriously, you can make it fun for kids. Obese kids can benefit with weight training in another way. They can accomplish and stick to these weight training programs easier, whereas some programs may be tougher for them, like running.
Leaning the basics of good form and safety should come first. Using a variety of tools such as dumbbells, resistance bands, medicine balls and body-weight exercises will make the workout more fun. I like to do 2 sets of each exercise with kids, making sure to hit each muscle group. I typically have them perform 10-12 repetitions per set and then move up in weight when it gets to easy. Just like any other weight training regime, a day of rest between muscle groups is important for injury prevention and optimal muscle strength.
Kids do pushups in school (or at least try to!). The fact is, pressing 10 pound dumbbells is easier than that! Make it fun for them, build their confidence and give them a healthy habit that will last a lifetime!