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The Ultimate Runner’s Guide to Stress Fractures: Causes, Risk Factors and How to Return to Training

Posted Dec 28 2012 6:00am

stress fracture runningA stress fracture is one of the most frustrating injuries a runner can come down with .

While bad cases of some injuries do have a reputation for sticking around longer than the duration of a normal stress fracture, a stress fracture is a much bigger baseline setback than most soft tissue injuries: at least six weeks of no running at all—some of your time off may even need to be on crutches or in a “boot.”

As the name suggests, a stress fracture is a small crack in any of the weight-bearing bones of the body. Runners can get a wide variety of stress fractures, but the most common locations are (in order) the tibia, the metatarsals, the femur, the fibula and the navicular.

Varying degrees of stress fractures

Stress fractures can be grouped into “low risk” and “high risk” categories:

A low risk stress fracture will typically heal on its own just fine, and may not even require any time spent in a boot or on crutches. Low risk stress fractures include most types of tibial stress fracture, fibular stress fracture, and metatarsal stress fracture.

A high risk stress fracture, however, is one in an area which is known to heal poorly. Stress fractures to the navicular, pelvis, and femur, however, are often high-risk, and tend to require significantly more time away from running and a more cautious approach to returning to running. Fortunately, these high-risk stress fractures are rarer than the low-risk types.

Stress fractures above the knee are particularly troubling from a medical standpoint, as the femur, pelvis, and low back are among the strongest bones in the body. A stress fracture to these areas may indicate underlying medical problems.

Why runners are prone to stress fractures

Bone, like most tissue in the body, can adapt and become stronger when it’s subjected to a stress . However, unlike muscles and tendons, which can adapt and strengthen in a period of days or weeks, it takes many months for bone to become stronger after it’s been put under an increased level of stress.

In fact, there’s even a window of about a month where bone becomes weaker after an increase in training stress because of the way the body remodels bone. Your body first tears out some walls in the bone structure before it can put in new ones, much like remodeling your house.

A stress fracture typically feels like an aching or burning localized pain somewhere along a bone. Usually, it will hurt to press on it, and the pain will get progressively worse as you run on it, eventually hurting while walking or even when you’re not putting any weight on it at all. Sometimes, if the stress fracture is along a bone that has a lot of muscles around it, like the tibia or femur, these muscles will feel very tight.

If you suspect you have a stress fracture, you should see an orthopedist as soon as possible to get it diagnosed. X-rays are nearly useless for diagnostic purposes, so your doctor should conduct a bone scan or, preferably, an MRI to confirm the presence of a stress fracture.

While bone scans are highly accurate and reliable, they are very expensive. An MRI can allow your doctor to get a better idea of the severity of your stress fracture, which might allow him or her to give you a better estimate of when you can return to training.

Sometimes, you can catch a stress fracture early on—at this point, it is classified as a stress reaction and may only require a few weeks’ time away from running. It’s very important to heed your doctor’s advice, since continuing to run on a stress fracture can cause it to progress to a real bone fracture, which will land you on crutches for several months and will put any future running in real jeopardy. This is especially true with high-risk stress fractures.

What causes stress fractures

The scientific literature is unclear on whether the main cause of stress fractures is impact loading forces or active forces.

Impact loading force is the degree of shock that travels up your foot and leg when you initially hit the ground, while active forces are generated when you are pushing your body off the ground.

Some research has found that runners with a history of tibial stress fractures have high impact loading rates, while other studies have predicted that the strain on the bones of the body is greatest when pushing off the ground. Fortunately, these two are not mutually exclusive—strategies that can reduce impact loading rates will also likely reduce active forces.

Because there’s no known treatment, aside from rest, that can speed your recovery from a stress fracture, most research has been directed at methods to prevent a stress fracture in the first place (or avoid another one in the future). Strategies for prevention are mostly focused on reducing the stress on your bones and building or maintaining their strength.

Avoiding stress fractures

Since a stress fracture is a fairly serious injury, sustaining one warrants a thorough examination of your training, running mechanics, and overall health.

First off, you need to examine your training history to see if you made any drastic changes in mileage or intensity in the past month or so.

As mentioned in the introduction, when bone is stressed, it is actually weaker for about a month after a change in training stress before it becomes stronger. Become of this, it may make more sense to change up how you increase mileage.

While the traditional recommendation is a 10% increase in mileage every week , the dynamics of bone remodeling suggest that taking “down weeks” every 3-4 weeks with a 10-20% drop in mileage might be a better idea. A series of weeks under this model might look like this:


Another option is an “equilibrium” model, where mileage jumps 20-30% every 3-4 weeks, but with no change of mileage in the intermittent weeks. A series of weeks under the equilibrium model might look like this:


Other risk factors for stress fractures

But training is far from the only important factor. Many runners can run well over 100 miles a week without developing a stress fracture, while others come down with them at 15 or 20 miles a week.

One reason changes in training do play a role is that the bone’s capability to handle stress is directly related to its size and strength.

Multiple studies have connected narrow, weak bones with an increased risk of stress fracture. Furthermore, it appears that the muscles surrounding a bone influence its size and strength as well.

One study found that women with a larger calf circumference are at a lower risk of tibial stress fracture, and another found that women with larger muscular cross-sectional area in their calf were at a lower risk of any kind of stress fracture.

While you probably won’t be able to do any strength training during your recovery, improving the strength, size, and endurance of the muscles in your legs —especially your calves—is a good strategy for the future.

The speed at which you train is also something to take into consideration . Many dedicated runners run themselves into trouble by maintaining a fast pace on many of their runs. Since both impact and active forces have been connected to stress fractures, it makes sense that a faster training pace would make you more vulnerable: running fast necessarily means incurring greater impact and active forces when your feet hit the ground. If you are a speed demon on your easy days, think about dialing back the pace once you’re beginning your comeback.

Stride frequency is another factor that affects your impact and active forces. To run a given pace with a low stride frequency, you’ll be hitting the ground and pushing off harder than if you were running with a higher stride frequency. Of course, there are upper limits on how high of a stride frequency you can maintain. But elite runners (and, in my experience, runners who are better at avoiding injury) tend to maintain a stride frequency of 180 steps per minute or more, even at slow paces.

Finally, stress fractures may be indicative of underlying health issues, especially in women. Because of the hormonal dynamics of the menstrual cycle, women who miss their period because of insufficient caloric intake in their diet are at a significantly higher risk for sustaining a stress fracture. If you are amenhorreic (missing your monthly period), you should talk to your doctor as soon as possible, as it can affect not only your immediate injury risk, but your bone density for the rest of your life, which is a problem much bigger than a running injury.

Recovery and treatment of stress fractures

If you suspect you have a stress fracture, you need to see a podiatrist or an orthopedist to have it diagnosed. They will be able to determine the exact location and severity of your stress fracture, as well as what, if any, protective measures (boot, crutches, etc.) you will need to take while it heals.

It is exceptionally important to heed the advice of your doctor when it comes to stress fractures, because pushing too hard on a stress fracture can put your running in jeopardy for months to come.

While you recover, your doctor will probably lay out a schedule of when you can return to various cross-training activities . Some non-weight bearing cross training methods, like aquajogging , can often be started right away, though you may have to wait several weeks to be able to use the elliptical or exercise bike. Again, this depends on the specifics of your stress fracture, and is something you’ll want to ask your doctor about. Maintaining your aerobic fitness while you are injured is not always fun, but will make your comeback a lot easier once you’ve been cleared to run again.

Use your recovery time to review your training, diet ( 5 foods that might be robbing your bones of calcium ), and lifestyle to identify factors that might have contributed to your injury.

Taking a calcium and vitamin D supplement which provides 200% of your RDV of both nutrients is not a bad idea either, as a 2007 study found that this can reduce the risk of a stress fracture in female Navy recruits.

As you return to running after your time off, examine your running form, with particular attention to your stride rate and usual training pace, since a low cadence or excessively fast everyday speed can increase loading through your foot, lower leg, thighs, and hips, causing problems if you are susceptible to stress fractures.

Outline of preventative measures

These are simple, well-backed by research, and carry a relatively low risk of extra complications. These preventative measures should be taken by anyone who’s suffered a stress fracture, or believes that they are at risk for one.

  • Examine your training to see whether you made any drastic changes in volume or intensity in the past month or so. These may have caused your stress fracture, as bone becomes more vulnerable to injury in the month following an increase in stress. Consider changing to a training model which includes “down weeks” every 3-4 weeks or an “equilibrium” model which maintains new levels of mileage for longer before increasing again.
  • Check your stride frequency by counting how many times your right leg hits the ground in 30 seconds while running, then multiplying by four. Ideally, you’d be hitting 180 steps per minute or more. If you are significantly lower than this, do your best to increase your cadence by 5-10%. This will decrease the loads that have to be carried by your joints and bones.
  • Speak with your doctor to see whether you have any underlying health issues that could have contributed to your stress fracture. This is especially relevant for women, for whom amenorrhea is a major concern and also a major health risk even outside of running.
  • Once you have recovered, incorporate more lower-body strength training into your regimen. Muscle size and strength are linked to bone size and strength; additionally, there is some evidence that stronger muscles will absorb more shock, leaving the bone less vulnerable to high impact loading.
  • Re-examine lifestyle issues like a lack of sleep and improper diet which could impede your body’s ability to repair your bones.

These are preventative measures that have some backing evidence, but it is either circumstantial or only indirectly linked to bone stress. Additionally, they may carry the risk of increasing your risk for other injuries. If you have suffered multiple stress fractures and have not had success preventing them with conservative measures, consider trying these.

  • Try using a custom orthotic if you have a history of tibial or metatarsal stress fractures. Some doctors have proposed that custom orthotics can alter how forces are transmitted up your leg, theoretically leading to lower peak stresses on the bone. Be aware that this theory currently has no experimental evidence to back it up!
  • Alternatively, if you have a history of tibial or fibular stress fractures, you may also consider running in thin, low-profile “minimalist” shoes. Wearing a thin shoe will force you to maintain a high stride frequency, and will also encourage a midfoot or forefoot strike, which should reduce impact loads on your leg. The tradeoff for this is increased stress on your foot and metatarsals; some doctors have warned that wearing minimalist shoes can even increase your risk for a metatarsal stress fracture.
  • Take a calcium and vitamin D supplement that provides 200% of your RDV of both. This carries a small risk of kidney stones if your dietary calcium intake is already high, however.
  • Change the surface you typically run on. Many runners anecdotally report that soft, natural surfaces like dirt trails and grass fields feel kinder on their bodies than hard, even surfaces like roads and sidewalks. However, there’s no experimental evidence that runners that train on any particular surface are more or less at risk for injury. In fact, there’s some suggestion that soft surfaces may increase the loading on your bones somewhat , as they demand your body maintain a higher overall leg stiffness. This may be counterbalanced by the fact that soft surfaces are usually more irregular, and hence stress your body slightly differently every step. You’ll have to experiment with running surfaces to see what type you feel is more beneficial for you.

Returning to training fro a stress fracture

When it comes to returning to running, you will have to follow the directions of your doctor. Typically, stress fractures require 6-8 weeks away from running.

Once you begin to run again, you will likely start with very short sessions with alternating bouts of walking and jogging. One example might be six sets of 5min, each consisting of 1min of jogging and 4min of walking. This can gradually build up to 3-4min of jogging per 1min walking, and eventually progress into continuous runs.

Here is a sample 4 week return from stress fracture training schedule: Click here to expand»

You may experience some mild soreness in your initial runs because of the scar tissue and bone remodeling that’s happening at your injury site, but it should not resemble the pain you initially felt when you had a stress fracture. As long as the pain is mild, goes away quickly after your , and isn’t a dull lingering pain, you should be ok. Return to your doctor if you continue to have pain at the site of your injury.


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Monday 3 x 9 min walk, 1 min run + core + hips + lower leg strength
Tuesday 60 min ellipical medium
Wednesday 45 min elipitcal easy, 45 mins bike hard
Thursday 3 x 9 min walk, 1 min run + core + hips + lower leg strength
Friday 2 hours moderate bike/elliptical – simulate long run
Saturday 4 x 9 min walk, 1 min run + core + hips + lower leg strength
Sunday Cross training – outdoors
Monday 3 x 8 min walk, 2 min run + core + hips + lower leg strength
Tuesday 60 min ellipical medium
Wednesday 45 min elipitcal easy, 45 mins bike hard
Thursday 4 x 8 min walk, 2 min run + core + hips + lower leg strength
Friday 2 hours moderate bike/elliptical – simulate long run
Saturday 4 x 8 min walk, 2 min run + core + hips + lower leg strength
Sunday Cross training – outdoors
Monday 4 x 6 min walk, 4 min run + core + hips + lower leg strength
Tuesday 60 min ellipical medium
Wednesday 45 min elipitcal easy, 45 mins bike hard
Thursday 5 x 6 min walk, 4 min run + core + hips + lower leg strength
Friday 2 hours moderate bike/elliptical – simulate long run
Saturday 5 x 5 min walk, 5 min run + core + hips + lower leg strength
Sunday Cross training – outdoors
Monday 6 x 5 min walk, 5 min run + core + hips + lower leg strength
Tuesday 60 min ellipical medium
Wednesday 45 min elipitcal easy, 45 mins bike hard
Thursday 6 x 5 min walk, 6 min run + core + hips + lower leg strength
Friday Off – rest day
Saturday 3 mile run
Sunday Cross training – outdoors
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