The most suitable age for fitness is high school, that is, after 16 years old, your physical development has begun to bear, so you can carry out systematic bodybuilding training and increase the weight lifting load, because you are mature at this time and will not affect your development. At this time, the efficiency of fitness training is high. When the age reaches 17- 19, the muscles grow fastest, the bones tend to thicken, the shoulder blades tend to widen, and the upper body will soon become strong. In addition to becoming more horizontal, the upper body can also become taller and the bones will grow accordingly. .