Most males have reached their full height by age 16, but their muscles still grow. Much of the height increase comes from a growth spurt between ages 12 and 16. During this period, boys often add as many as 12 inches. They also put on weight, and this gain typically ranges from 15 to 65 pounds.
A male's growth spurts begins in the extremities. Arms, hands, legs and feet grow faster than other body parts, which negatively impacts coordination. Teen boys sometimes seem clumsy, but they are just trying to adjust to the new sizes. The trouble lessens as the rest of the body starts to grow, as well. During adolescence, boys undergo a tremendous number of body changes in addition to becoming taller and heavier. Body hair begins to appear, first in the pubic region, then under the arms and on the face. A boy's larynx grows, and his vocal chords lengthen. This results in the ordinary but embarrassing stage of voice cracking, as his voice begins to move into a lower register. Skin becomes more oily, which leads to acne breakouts. During late adolescence, a boy's body starts to become fuller. The chest and shoulders are broader, and the entire upper body has noticeably more muscles.