How Young is Too Young To Run an Ultramarathon?


By Adam St. Pierre,
CTS Ultrarunning Coach

Ultrarunning is often thought of as an older athlete’s game. Often, there are considerably more athletes in the 40+ age groups than the younger age groups, primarily because that’s the population more interested in running ultramarathons. But as parents run longer distances and inspire their children and teens to start running, should ultramarathons put minimum age limits in place? Is it safe for a 12-year-old to train for and run a marathon, let alone a 50k? Is a 16-year-old physically mature enough to handle the training and race-day stress of a 100-miler?

In Neil Armstrong’s 2006 textbook, Paediatric Exercise Physiology, the author reminds us, “Children are not mini-adults.” With this in mind, it is hard to draw black and white conclusions about the appropriateness of training and racing for young athletes, as there is a lot of individual variability and so few are involved in long distance running. According to a survey done in 2013 by Ultrarunning Magazine less than 1% of all ultramarathon participants are younger than 20 years old.

Physical Readiness

It is known that young athletes can improve muscular strength, anaerobic power, and aerobic fitness with exercise training, but not necessarily to the same degree that similar training would lead to in an adult. Ultrarunning requires a high level of aerobic fitness, but also a degree of tissue (bone, muscle, tendon, and ligament) strength for the body to handle the distance. Just as aerobic fitness increases with each workout over weeks, months, years… so too does tissue tolerance. I think back to how sore I was after my first ever 20 mile run, but now after 10+ years of consistent endurance run training, I don’t experience that soreness at the same level.

Endurance training is cumulative over years and decades. We get stronger by building on the all the training we’ve previously done, not just the most recent training block. There is no evidence I have seen that says young athletes, even prepubescent athletes, should not run ultramarathons. However, it is very difficult for a young athlete to accumulate the long-term physiological and anatomic adaptations that are helpful for sustaining the training required to prepare for ultradistance events. It would seem that age itself is less of a limiting factor, but that the time required to progress gradually and sustainably means not many children and teens are physically ready to train for ultramarathons.

How Youth Sports Are Organized

Most organized endurance sports have a progressive system of racing for young athletes. In XC skiing, 8-10 year old athletes typically race 1-2km, 11-13 year olds might race 2-3km, 14-15 year olds typically race 5km, 16-19 year olds might race 1-30km, and adult athletes may race anywhere from 1-50km. In cyclocross or road cycling criteriums, junior athletes might race for 20-30 minutes while adults race for 40-60 minutes. At the USA Track and Field Youth Championships, all age groups can race in the 100, 200, 400, and 800m races. Only athletes older than 13 can compete in the 1500m. The longest event contested at the meet is the 3000 (whereas adult athletes may run 10k on the track). My point being, sport National Governing Bodies create guidelines aimed to steer the development of young athletes toward events or competition lengths and formats that mimic Olympic, World Cup, or World Championship events. The general theory being, it’s important for young athletes to learn how to go fast before they learn how to go long, so keep their competitive events short to encourage high speeds of competition.

Ultrarunning doesn’t necessarily play by the same rules. There is no single governing body and there are no ultras at the Olympics are at the NCAA level. Some races prohibit athletes younger than 18 from participating, others do not. There are examples of young runners doing very well at ultradistances. A quick perusal of Andrew Miller’s results shows teenagers can not only complete but also compete in all distances up to and including 100 milers! Andrew Miller’s own first Ultrasignup result is from the McDonald Forest 15km at age 13. He ran a 50km at 14, and 3 more at 15, 8 races from 50k-50miles as a 16 year old. He ran his first 100 miler at 17 years old- placing 3rd at Pine to Palm in 2013. He won or podiumed at more races as an 18-19 year old. He won Western States at 20. I don’t know Andrew personally (but am certainly a big fan!) and I bring him up here merely as an example that young athletes can be great at ultradistances. I’d also like to point out that Andrew ran ultras for 3-4 years prior to running his first 100 miler. I invite anyone who knows Andrew (or Andrew himself!) to correct me if I am wrong!

Why Kids and Teens Don’t Run Ultras

I think young runners are dissuaded from participation in ultrarunning for a number of reasons. I think a lot of young runners are steered into more typical organized sports, whether at a scholastic or club level, possibly to try to procure a college scholarship. In the case of running, most schools and clubs are focused on cross country or track and field and target the shorter events National Governing Bodies promote for their age group. We all know that racing 5km can be good for ultramarathon training (, but is ultramarathon training good for 5km performance? I would say yes, but I think it takes a patient athlete to see the pay off.

There’s also the matter of interest and emotional readiness. Some kids and teens are not emotionally ready to commit to structured training, and may even struggle to engage during practices for youth team sports. That’s not necessarily a problem, it’s just part of each kid’s personal development. Similarly, teens may simply not be interested in running long distances at relatively slow speeds, or focusing on events that require several months of training.

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Another reason young runners may be discouraged from running ultramarathons is the notion that running long distances will “ruin your knees” or “stunt your growth” (both myths, as shown here and here). That being said, a number of factors can predispose a young athlete to injury when undertaking run training; among them footwear, biomechanics, and strength and flexibility imbalances. The biggest factor, however, is improper training intensity and/or volume. Young runners must gradually build up their training volume and ensure the bulk of running is done at a sufficiently easy intensity. Too much hard running is the biggest mistake I see in young athletes. The other key to successful run training in young athletes is energy balance. Growing bodies need fuel. Growing bodies undertaking exercise training need even more fuel!

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Should Ultras Recruit Kids?

Probably not, but there don’t seem to be compelling reasons why kids shouldn’t be allowed to run an ultra if they want to. The key is that parents, coaches, and even doctors should pay close attention to a young athlete’s preparation and participation. Race directors are rightly concerned about liability issues concerning minors on the racecourse, and perhaps one solution would be to require full-course pacers for athletes under a certain age.

It is also important to note that much research on long term outcomes in sport show that kids who are among the best competitors at 12 are often not the best at 18, and unfortunately, many of those kids are no longer involved in sport at all at 20. Most research shows that the most successful adult athletes were involved in a variety of sports and activities throughout adolescence. Risk of injury is higher in athletes who specialize early in one sport. Unfortunately, many athletes, parents, and coaches encourage young athletes to specialize early in order to get a “leg up” on the competition- perhaps encouraged by the so called “10,000 hour rule” made popular by Malcolm Gladwell in “Outliers.”

So, if you are a young athlete interested in running ultra distances, or the parent of a young athlete interested in running ultra distances, here are my conclusions:

  • Go for it and have fun, but listen to your body.
  • Ensure the bulk of your running is done at a sufficiently easy intensity
  • Build up your run volume slowly. Give your body time to adapt to the stress and get stronger. Be patient!
  • Participate in a variety of sports and activities in addition to running: cycling, swimming, XC skiing, alpine skiing, tennis, soccer, martial arts, dance, weight lifting, basketball, etc.
  • Make sure you’re eating enough. Inadequate energy intake prevents the body from adapting positively to training and hinders recovery.
  • Get plenty of sleep. The more you do with your body the more rest it needs to recover and adapt. Young athletes are not great at recognizing this themselves, so parents and coaches should keep an eye on kids’ sleep habits.

Comments 4



  3. Hello, I have a 12 year old grandson that is ADHD and loves trail running. He has finished an 18 mile at age 9, 32 mile at age 10, 50K at age 11 and is entered in a 52 mile at age 12. He is very motivated to finish and doesn’t go for speed in the events he has done. Recovery has been minor and he has been injury free. Trails make him happy so I say go for it if your young one wants to run ultras. As the article states, keep a close eye on the sleeping, eating, and health of your young one.

  4. Great read. We have an 11 year old who is training for his first official ultra. He’s done a few marathons, 1/2s. 10ks , lots of long training runs and an unofficial 50 Mile Grand Canyon run /hike in 20 hours .He also read this article so he can continue to grow and learn as a young athlete . You can check out his YouTube video as well

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