12 years old, practicing chest muscles, abdominal muscles and arm muscles. I am 12 years old and want to practice chest muscles, abdominal muscles and arm muscles. How to practice can not only increase muscle but also affect height. In your case, my advice as a fitness instructor is not to exercise excessively. It is easy to have problems when growing up.

Of course, a little exercise can do it. Step by step, if you have a small dumbbell, do simple actions, such as bending your arm and lifting the dumbbell.