How Young Is Too Young to Run?

Nicholas Sullivan ran his first race at age 7. It was only a mile, and it wasn't enough for the now fourth-grader in Little Silver, New Jersey. "He just kept saying he wanted to run more, he wanted to run the 5K, 5K, 5K," says Nicholas' dad, Bob Sullivan, a former professional tennis player who now coaches.

So Nicholas spent the summer running with his parents, slowly building up from 1 mile to 3 miles, one half-mile at a time. By the fall, at age 8, he tackled the 5K, clocking in at an impressive 28 minutes. The next year, at age 9, he ran it in 22 minutes. This past fall, at age 10, Nicholas crossed the finish line in under 20 minutes. "Over the last three years, he's gotten to be very good -- like off the charts good," Sullivan says.

So good, in fact, that other parents in his neighborhood have suggested he try out for the junior Olympics. That's when Sullivan pulled the breaks.

"As a coach, it's easy for me to want to become overly structured with anything," says Sullivan, who's run 31 marathons. "But given [Nicholas'] age, I've been the exact opposite. All I've been trying to do is keep it fun -- fun, fun, fun."

Sullivan's approach is the right one, say experts who study and treat young athletes. While there's no question that physical activity in youth is critical for physical and mental health, as well as for developing lifelong healthy habits, how exercise is presented and pursued matters, says Skye Donovan, a physical therapist and associate professor of physical therapy at Marymount University, who researches childhood obesity.

On one end of the spectrum, she says, there are overweight and obese kids who never find sports they like, which raises their risk for obesity as adults. On the other end, there are kids whose parents pressure them into a sport, leading to burnout, "and now they don't want to do it anymore," she says. "So we can have two totally different prongs coming in with the same results of having people not engaged in lifelong fitness."

Growing Bodies

The son of two runners, Nicholas didn't need any convincing to take up the sport. "It's just so much fun," he says. "I love to run with my mom and my dad." But just because he often runs with his parents doesn't mean he does, or should, maintain an adult's exercise regimen. These days, Nicholas runs up to 25 miles a week -- spread between four days -- while his dad runs closer to 50 miles weekly.

So far, Sullivan says, he and his wife have been "very, very careful with how much he runs because now he really likes it, and he's showing a lot of natural talent for it."

Tailoring children's exercise habits to their age is important, says Donovan, a runner and volunteer marathon coach through the Leukemia & Lymphoma Society's Team in Training Program. "Kids are not just little adults -- they have different physiology," she says. For instance, children take in more heat on a hot day and lose more heat on a cold day than adults due to their greater body surface area to body mass ratio, according to the International Marathon Medical Directors Association, which discourages marathon running before age 18.

Kids also face unique risks when it comes to overuse injuries. For example, children's bones grow faster than muscle tendons during growth spurts, which can affect their flexibility and make them more prone to injury, IMMDA says. Given their shorter strides, kids also pound the pavement more often per mile, which increases the risk of stress fractures.

"The longer they're doing this repetitive activity at this young of an age without having appropriate muscle development, and [without] having a coach help them with flexibility training and strength training, that really kind of puts them at risk for developing injuries long term," Donovan says.

A Pressure Cooker

There are also psychological concerns with young runners, says Dr. Andrew Gregory, an associate professor of orthopedics and pediatrics at Vanderbilt University School of Medicine, where he mostly treats injuries in young athletes. For example, sports like running that tend to value a leaner physique might spur body image issues early in life and eating disorders later.

"In order to be good runners, most people believe that you have to be a certain build or body type," Gregory says. "If you're made that way, it's easy. If you're not made that way, then it can be a challenge."

An emphasis on competition rather than enjoyment can also be a problem for children. For example, when kids know their parents have paid a lot of money for them to join an elite league, or that they're being primed for a college scholarship, the activity can lose its fun factor, Donovan says. "We're actually seeing a lot more psychological issues with the kids because of the pressure they feel on themselves," she says.

That pressure can backfire: Kids can feel like failures and experience emotional burnout -- "a real phenomenon that can have the exact opposite effect of that intended by participation," according to IMMDA. That's precisely what Sullivan hopes to avoid, and for now, he's opted against competitions for Nicholas outside of an occasional neighborhood race.

"I'm a big believer in moderation ... you can't coach desire," Sullivan says. "I wanted to be very careful not to get him feeling like it's a job."

What's 'Too Young?'

There's no hard-and-fast rule about how young is too young to run, or how long is too long for various ages, but there are some good guidelines, Gregory says. Among them: Take at least one day a week off from sports, and only participate on one team at a time. Limiting kids' hours of exercise per week to less than their age is another good rule of thumb, he says.

Donovan recommends children who show an interest in running try short races geared for kids, "and then let them be your guide as to what they can do." Some signs they've gone too far? They're dramatically changing color, substantially slowing down their pace or gulping excessive amounts of water during runs, or they're recovering slowly or complaining of pain or discomfort afterward. "Those are all signals that this might be a little too vigorous," she says.

The most important thing, Donovan says, is to introduce kids to a variety of physical activities so they can "become lifelong lovers of fitness." What's more, an early introduction to athletics helps prevent obesity, diabetes and heart disease, as well as boosts mental health, Gregory adds. Running, he says, "is just one of those things that all kids should be exposed to at some point because it could be an activity they really enjoy." If they don't? Move on.

Nicholas, for one, won't be moving on. When asked whether he'll continue with the sport, he didn't hesitate. "Yes, definitely," he said. "I love it."