If you have teenagers — or were once a teenager — you’ve probably encountered this: Your child’s jeans fit perfectly in September, but by December the ankles are showing. The growth spurt in teens can be surprisingly rapid, with some teens growing 4 to 5 inches (10 to 13 centimeters) in one year. But is this really the fastest period of human growth?
Surprisingly not: The teenage growth spurt is the second fastest that humans can grow.
Children can add approximately 1 foot (25 to 30 cm) of height per year — more than twice the rate of the most dramatic growth spurts in adolescence.
In fact, for girls, “by 18 months, they will be 50% of their adult size.” Adam Baxter JonesThe professor at the Faculty of Kinesiology at the University of Saskatchewan in Canada told Live Science. Boys reach 50% of their adult size at 24 months, he said.
Then things slow down. “When we reach late infancy and childhood, physical development is put on the back burner,” Cumming said.
Growth decreases to about 2 to 2.5 inches (5 to 6 centimeters) per year from age 4 until adulthood, according to Baxter Jones. This is when humans reach their second fastest period of growth.
At their peak during puberty, girls grow an average of 3.5 inches (9 centimeters) per year, and boys grow an average of 4 inches (10 centimeters) per year, according to a study conducted at Harvard University. Journal of Adolescent Health.
But these average maximum growth rates are just averages.
“If we measure regularly enough, what we see are these periods of really intense growth, and then the body adapts,” Cumming said. “We can see rates anywhere up to about 20cm [nearly 8 inches per year] In some of the studies that we looked at… of course, if you average that over a period of time, [you get] 10 to 12 cm [4 to almost 5 inches] “Every year.”
Just as they did when they were children, girls go through growth spurts earlier — around age 11, while boys typically reach puberty about two years later.
“Boys usually have a slightly more intense growth spurt,” Cumming said. “This is because they produce more growth hormone, but also testosterone, which also contributes to bone length.”
The pubertal growth spurt stops at around age 16 for girls and 18 for boys, and because boys have such intense growth and grow for about two years, they end up being taller on average.
The age at which a person achieves their growth spurt does not affect their final height – a person who matures early stops growing earlier than a person who matures late, so a person who matures late has more time Baxter Jones said.
Growth spurts and body shape
Growth spurts occur from the outside in. “First, the feet and hands, then the long legs and long arms. That’s why you see kids at the beginning of puberty, they look like little giraffes. They have these big clown feet, and these legs that go on forever,” Cumming said.
The trunk grows last, and if a child develops late, sometimes the trunk cannot catch up with the rest of the body. As a result, in sports like ballet and gymnastics, teams choose late developers because they have a more linear physique and longer legs, according to Cumming. However, early developers have their own mathematical advantages.
“If you get a growth spurt in puberty early, you’re bigger and stronger. These are the kids who get selected for all the top positions and into the top academies,” Cumming said. “At Scottish Academies we surveyed over a thousand children over the age of 14. We found no late developers at all.”
But this rapid growth comes at a cost. During growth spurts, bones are weaker and more susceptible to damage.
“Your bones grow, then they mineralize. There’s about a nine-month gap,” Baxter-Jones said. “The peak fracture rate is during the adolescent growth spurt.”
Muscles and tendons also take up to nine months to catch up with developing bones, which can lead to growth-related injuries, especially around the heel, knee, and lower back.
However, carefully monitoring growth spurts can help prevent more serious problems. “If we did that in the Premier League academies, we could reduce those non-contact injuries by about 70%,” Cumming said.
For parents wondering if their child’s growth pattern is normal, both experts stressed that wide variation is to be expected.
“It’s normal to grow quickly, but it’s also normal to grow slowly,” Baxter-Jones said. Final adult height comes down to genetics. There are also rare cases in children, such as: Giant pituitary glandWhich leads to excessive production of growth hormone. Children with this condition can even grow old 6 inches (15 cm) per year, and One report documented a 13-year-old boy growing at a rate of 7.5 inches (19 cm) per year. But even this rapid growth is less than the growth rate of children.
So what is the fastest a human can grow? The answer is not when you stretch your jeans as a teenager, but rather when you are so young that you don’t remember it ever happening.