I would like to know when in stage 3 does the growth spurt occur for boys. How long does the spurt last?
Dr. Tanner, many years ago, developed a system of classifying the progress people make in changing from a child's body to an adult body. He divided it into five stages. The first stage is a child, the fifth stage is an adult, and three stages in between are adolescence. Stage two starts when signs of puberty can first be seen externally. Stage three is the rapid growth stage. Stage four is when growth slows down. For boys, each stage of adolescence lasts about two years -- for some it is more, for others it is less.
So by definition, stage three is the period of time you are growing rapidly. Since you were about five years old, you have been growing about 1 to 2 inches per year. That is the typical growth of children. Stage 3 is defined as the time when that rate of growth changes. It can go from 2 up to 8 inches per year during stage 3. The rate of growth doesn't stay steady, but it peeks in the middle of stage three. Stage 4 is then then defined as when your rate of growth drops down to childhood speed or lower (1 to 2 inches per year). Stage 5 is when all growth in height stops.