John Davis

Written by John Davis


Does Training for the Ultramarathon Increase Injury Risk? Is it even Healthy?

Ultramarathoners are a different breed

You might have heard something similar to that in your running life, and it sounds pretty reasonable.  The stresses of training for and racing an ultramarathon are distinct in many ways from recreational running or even training and racing shorter races.

For runners whose main focus is the ultramarathon, these stresses become a way of life.

But are ultramarathoners really that different from the rest of the running population? Do they get the same kinds of injuries? Is running that far good for your health?

These are broad questions, and to answer them, you’d need an equally broad scientific study.  Fortunately, just such a project is underway thanks to a study headed Martin Hoffman of the University of California-Davis and Eswar Krishnan of Stanford University.

The ULTRA in marathon

The Ultrarunners Longitudinal Tracking Study (ULTRA, cleverly) is a long-term investigation into the health and well-being of a group of over 1,200 ultramarathon runners.

By tracking these runners over the course of many years, we can get a better understanding of how training for and racing ultramarathons impacts your risk of developing running injuries as well as your overall health.  This study will also function as a test of the health effects of high volumes of exercise in general.

Ultramarathon and running injuries

The ULTRA study began in 2011, and Hoffman and Krishnan have began publishing their preliminary findings.  Although it will take at least 10 or 15 years to get good data on some questions (like “is running high mileage over many years bad for your heart?”), the baseline results nevertheless provide good information on running injuries in the ultramarathon community.

Broadly, ultramarathoners aren’t too different from the rest of us when it comes to injuries.

Hoffman and Krishnan found that 77% of the 1,212 participants in the study had suffered at least one injury during the past year which had impeded their ability to run.

This is on the high end of injury rates among runners, but other studies examine recreational runners doing lower mileage—the entire group in the ULTRA study averaged over 2,000 miles in the previous calendar year.

Considering that this includes days missed from injury, as well as the recovery periods after ultra races, that’s pretty impressive.

The ultramarathoners who did suffer an injury averaged two distinct injuries per year.  The typical injured runner missed 14 days of running because of any running-related injury in the past year, which implies that most of the injuries were not serious.

Things get interesting when we start to pry into the details.

Stress fractures

The most common injuries are the usual suspects—the knee, the Achilles tendon, the calf, the plantar fascia—but the incidence of stress fractures in ultramarathoners is somewhat lower than what’s been measured by other studies.

Only 5.5% of the study’s participants had suffered from a stress fracture in the previous year.

Additionally, tibial stress fractures, which are usually the most common type of stress fracture in runners, made up a smaller portion of the stress fractures in the ultra runners.  Instead, the most common stress fracture location in the ULTRA study was the metatarsals, the bones which make up your forefoot.

The authors hypothesized that the dirt and gravel trails that many ultramarathoners train and compete on might reduce stress on the shins, but at the expense of increased stress on the foot because of the irregular terrain.

Footwear might also play a role—trail shoes tend to be flatter and have less cushioning, which might also transfer stress from the lower leg to the foot. Of course, many ultramarathoners are now tuning to maximal cushion shoes, like the Hoka One One.

Running injuries vs male and female runners

Men made up the majority of the study’s participants, but a sizeable number (388) were women.  Previous research has found that women tend to be at a higher risk for running injuries than men, but the ULTRA study found no such distinction.

Women were at a higher risk for stress fractures, but their overall injury rate was the same as the men’s.

It’s not immediately apparent why this is; on one hand, it could be something intrinsic about ultramarathon training, but the possibility also exists that more injury-prone women never bothered with ultramarathons in the first place.


By comparing the group of runners who suffered injuries in the past year to those who stayed injury-free, Hoffman and Krishnan were able to conclude that the healthy runners tended to be older, more experienced at ultra running, and did a lower percentage of their training at a “high intensity” (what exactly constituted high intensity training was not explained).

Mileage was not a factor in injury rates overall, but running more miles did put you at a higher risk for a stress fracture.  Predictably, runners with a previous history of stress fractures (about one quarter of the runners in the study) were at a higher risk of suffering one in the past calendar year.

So, are ultramarathoners truly a different breed? At the end of the day, ultramarathoning is still just running.

  • Ultra runners are still vulnerable to the same old injuries in their knees, their lower legs, and their feet, but there are some important differences.
  • Ultramarathoners tend to suffer somewhat fewer bone injuries, and when they do get stress fractures, they are more likely to get them in the metatarsals.
  • Being older, having more ultramarathoning experience, and keeping the volume of high-intensity training under control all protect ultra runners from injury.
  • Being female and running higher mileage are connected with your risk of getting a stress fracture, but not injury risk overall.

Over the next several years, we’re likely to get periodic updates from the ULTRA study on how high volume running impacts injuries, health, and well-being.  It may take a while, but there is a good chance a lot of the “big questions” about running and health will be answered.

What’s your experience training for ultra marathons? Did you notice a difference in your injury susceptibility?

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1. Lucia, A.; Hoffman, M. D.; Krishnan, E., Health and Exercise-Related Medical Issues among 1,212 Ultramarathon Runners: Baseline Findings from the Ultrarunners Longitudinal TRAcking (ULTRA) Study. PLoS ONE 2014, 9 (1), e83867.
2. Barrow, G. W.; Saha, S., Menstrual irregularity and stress fractures in collegiate female distance runners. American Journal of Sports Medicine 1988, 16 (3), 209-216.
3. Taunton, J.; Ryan, M.; Clement, D.; McKenzie, D.; Lloyd-Smith, D.; Zumbo, B., A retrospective case-control analysis of 2002 running injuries. British Journal of Sports Medicine 2002, 36, 95-101.

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