As the age of onset of puberty varies, so too, does the length of time in each stage. Breast budding is most frequently the first physical sign of puberty. Breast development and pubic hair development can progress at different rates and be at a different SMR level at any given time. On average, adolescent females'growth spurt starts about one year before breast development begins. Peak height velocity is reached about one year and one month after breast development begins.
Testicular enlargement is most commonly the first physical sign of puberty in males.
See Table 1 for male SMR parameters. The average length of time for completion of puberty in males is three years.