This is an awesome question asked by a client. Kids should be taught and influenced by their parents to become physically active on an early age, as early as 2 years old. However, age appropriate exercises are paramount for each age: From 2 to 8, the emphasis should be on playing more than sports. Anything from climbing, swings, slides, and any gentle jumping activities should be encouraged. At this age, I would completely avoid any weights (such as dumbbells or even any resistance machines), since that would put undue stress on the kids' unfinished bone/joint growth and it can lead to medical issues. From age 8 to 13, the emphasis should be on light cardio (such as light jogging) or rope jumping, calisthenics (such as pushups, sit ups, squats, and light sports (if your kid in a sports program such as football or track and field, he should be supervised by a trained/licensed strength and conditioning coach). From age 13 to 18, I would begin to introduce light weight training, such as dumbbells and light resistance exercises, sports, and even encourage him/her to eat right and to observe his proper nutrition and enroll him/her in a sports program. If you have any questions, please feel free to contact me: There's no doubt that an early focus on your child's physiological developement can be paramount if they decide to adopt an athletic acreer as young adults. It's always great to start learning these fundamentals early.