Towards the end of puberty, boys go through a "growth spurt" which lasts for about two to three years. During this time, their body grows taller very quickly. When the growth spurt is at its fastest point, some people grow or more a year. This happens about two years after puberty starts, usually between the ages of 13 and 15. When a boy reaches the end of his growth spurt when he is about 18 years old, he will be at his adult height. His body will not grow much taller after that. Because of their growth spurt, boys' muscles can feel sore. These "growing pains" can feel worse if boys are active and do a lot of exercise. They go away after a while.