Proper strength training and moderate training intensity will not only affect your son's development, but also help him develop his body, strengthen his willpower and perseverance, be a strong and confident boy and help him grow up! There is no data showing that exercise affects height. People always think that short weightlifters are short, but they are not, because short people lift barbells much less than tall people, so weightlifters choose short people, so there is no tall weightlifter! 13 years old is not too early to exercise, it is very suitable. Don't worry, but the quality of personal trainers is uneven now, so pay attention! Children should not be given too much training!