I 15 years old, and now I am exercising my arms, wrists and fingers. When I want to practice my legs, my brother-in-law says (he also goes to the gym to exercise) that I will become a frog's leg when I practice my legs. What is the most important purpose of exercise? One is for good health, the other is for good health, and the other is both. Of course, if you are practicing martial arts and fighting, you need more professional guidance than reading books and watching videos. Simply put, balanced development, step by step, there will be no major health problems-genetic factors is another word. 15 years old is not suitable for practicing a certain part, unless you are a professional, a certain part has special requirements, or a certain part is weak. more specifically ...