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METATARSAL STRESS FRACTURES:

Do you have a sharp, aching pain on the top of your foot when you run? If so, it might be a metatarsal stress fracture. The metatarsals are perhaps the most elegant bones in your lower body.





The five long, slender bones extend from your midfoot to your toe joints, and despite their small size, must handle a tremendous amount of stress when you run. As a result, the metatarsal bones are a common location for stress fracture in runners.

If you have pain on the top of your foot or pain in your forefoot, you’ll want to read on. We have gathered scientific research on who gets metatarsal stress fractures, why they happen, how to prevent them, and how you can return to running as quickly as possible.

Metatarsal stress fractures cause a sharp, localized pain on the top of your foot. Weightbearing, especially in unsupportive shoes or barefoot, will often make the pain worse, and pushing on the top of your foot is usually very painful.

You might get aching or throbbing even when you aren’t putting weight on your foot. Swelling and bruising usually do not occur (if they do, see a doctor ASAP—chances are you have a full-on fracture of a bone in your foot!).


DIAGNOSIS: IS YOUR TOP OF FOOT PAIN A STRESS FRACTURE OR TENDONITIS?

If you are a runner with pain on the top of your foot, the cause is usually one of two things: either a metatarsal stress fracture or tendonitis in one of the extensor tendons that runs along the top of your foot. Fortunately, differentiating between extensor tendonitis and a stress fracture is fairly straightforward.


WHERE DO METATARSAL STRESS FRACTURES OCCUR?

Metatarsal stress fractures usually occur around the middle of the metatarsal bones, not at the base or at the head. If you do get pain at the head of a metatarsal, it’s more likely an injury to the metatarsal-phalangeal joint.

In terms of their distribution among the five metatarsals of the foot, stress fractures are most common in the second and third metatarsals—these two bones account for 71%of all metatarsal stress fractures.


Fourth metatarsal stress fractures are somewhat common, but in contrast, first metatarsal stress fractures are almost unheard of in distance runners.

While it’s possible to get a stress fracture in your fifth metatarsal, these are often associated with an acute rolling or jostling of your ankle—a sharp turn or cutting motion puts tension on the peroneus brevis tendon, which in turn pulls on the base of the fifth metatarsal, causing a fracture, so stress fractures to the fifth metatarsals are more often seen in activities like soccer, basketball, and ballet dancing.


THE RISK FACTORS AND CAUSES OF METATARSAL STRESS FRACTURE:


Metatarsal stress fractures are the second-most-common type of stress fracture in runners. They only account for about one percent of all running injuries, but because of their fairly long recovery time, they can be a pretty devastating injury.

Aside from runners, metatarsal stress fractures are also common among basketball players, ballet dancers, and military recruits. I haven’t encountered direct evidence that women are at higher risk of metatarsal stress fracture, but given that women are 1.5-2 times more likely for any type of stress fracture, it’s highly likely they are at higher risk for metatarsal stress fractures specifically.

Some indirect experimental evidence does suggest that minimalist shoes increase your risk for a metatarsal stress fracture. A 2013 study conducted out of Brigham Young University followed two groups of runners for 10 weeks.

One of the groups transitioned carefully to a minimalist shoe while the other group remained in their usual running shoes. The researchers used an MRI machine to capture any evidence of the early stages of stress fractures or top of foot pain in the feet of the runners in the study. They found that 10 of the 19 runners in the minimalist shoe group displayed evidence of bone marrow edema during the study, while zero of the 17 subjects in the control group developed bone marrow edema.


One valid counterargument to this finding is that bone marrow edema on an MRI does not necessarily mean injury is imminent—a different study on Stanford University cross country runners found that 43% of the team had bone marrow edema in their tibia at some point during the season, but none developed any shin pain that season or in the following year.

However, additional evidence may support a minimalist shoe/metatarsal stress fracture connection. Baseline findings from a cohort study on over 1,200 ultramarathoners found a lower rate of stress fractures in the tibia but a higher rate of stress fractures in the foot among ultramarathoners compared to previous research on road runners.

The more minimalist design of ultramarathon shoes is one possible explanation for this observation, although the rough terrain and hill climbs involved in ultra running may also play a role.


A shift to forefoot striking is the obvious explanation for why a minimalist shoe would increase your risk of a metatarsal stress fracture. However, the evidence for this hypothesis is similarly circumstantial. Forefoot runners must sustain greater forces underneath their metatarsal heads, so we might expect them to be at greater risk for metatarsal injury.

One computer modeling study suggest that forefoot strikers may experience greater metatarsal stress than rearfoot strikers, as well as a greater increase in metatarsal stress as a function of running speed.


This suggests that middle distance runners and sprinters would be at particularly high risk because they run fast with a forefoot strike (in minimalist shoes, no less!), but this has yet to be examined.


THE BIOMECHANICAL CAUSES OF METATARSAL STRESS FRACTURE


The most straightforward cause of metatarsal stress fracture is excessive loading on the metatarsal bones. People in sports that don’t involve heavy loading of the metatarsals—like swimming—don’t get metatarsal stress fractures.


But what’s “excessive”? Plenty of people run 100 miles a week or more, yet don’t suffer stress fracture. Clearly, there’s an interaction between how much you run, the way you run, and the internal structure of your body that determines whether or not you suffer a metatarsal stress fracture.


If you’ve read my articles on tibial stress fracture and medial tibial stress syndrome in runners—the two primary causes of running-related shin-pain—you know that bone geometry plays a major role in determining who suffers a shin injury. This makes sense: thicker, stronger bones are less likely to break, because they can spread out the same force over a greater area.


The distribution of metatarsal stress fractures within the foot gives a clue as to how bone geometry in the foot affects your risk for metatarsal stress fracture. The fact that metatarsal stress fractures are extremely rare in the first metatarsal—by far the largest, strongest, and shortest of the five—strongly suggests that bone geometry plays a significant role in determining injury risk.


WHY TOES PLAY A ROLE IN PREVENTING METATARSAL STRESS FRACTURE

Compared to the rest of your foot, your toes—and the muscles that control them—are stubby and small. The calf muscles, for example, which plantarflex the ankle, are vastly more powerful than the toe flexor muscles. Still, it appears that the toes play an important role when it comes to reducing stress on the metatarsal bones and offloading force from underneath the metatarsal heads during running.


The really interesting question is why long, tough training sessions increase strain in the metatarsal bones. The best explanation is, believe it or not, toe flexor fatigue. A number of studies support this conclusion:


First, a rather grisly but insightful experiment by Seth Donahue and Neil Sharkey at UC-Davis involved using a mechanical contraption hooked up to a human cadaver foot to simulate the effects of toe flexor fatigue on metatarsal bone strain

Long, fatiguing runs also appear to decrease your ability to use your toes to push off the ground. Research across multiple studies shows that, at the end of a long, difficult run (such as a military training march, a marathon, or even a 240-mile ultramarathon), you put more pressure under your forefoot and less pressure under your toes compared with how you run or walk when you’re fresh.


The tension from this muscular activity is transferred to the insertion point of the toe flexor muscles, which is on the backside of your fibula. All of this means that less force needs to be applied to the metatarsal head to achieve the same overall force acting on the body.

However, during a long run or a fatiguing workout, the toe flexor muscles become less able to produce force. Hence, your body shifts force from the toes onto the metatarsal heads, leading to an increase in metatarsal stress.


How do you stop this from happening and prevent a metatarsal stress fracture: Done barefoot on grass or astroturf. Unless otherwise noted, do 2 sets of each exercise for 20 meters.

*Walking with toes in *Walking with toes out *Walking with toes up *Walking with heels up / Walking with heels up backward *Walking on inside edge of feet *Walking on outside edge of feet *Side shuffle to left and right *Double-leg hops (30 reps) *Single leg calf raises (start with 10, progress over time to 30 or more)

Adding in toe crunches by trying to pick up a towel under your feet with your toes.


HOW TO PREVENT A METATARSAL STRESS FRACTURE:

As with all bone-related injuries, using “down weeks” every 3 to 4 weeks is a scientifically-supported way to allow bone to adapt and strengthen to a new stress. After exposure to a new stress, the body initiates the bone remodeling process. This is a fantastic capability—it’s what allows you to strengthen your bones over time.


However, the first step of this remodeling process involves your body eating away at old bone tissue to make room for new bone cells.

One consequence of this is that your bones are actually weaker for about 3-4 weeks following introduction of a new stress. After that, new bone cells start to mature and your bones strengthen again. This is borne out in observations of military recruits at boot camp—most stress fractures don’t occur right away; they occur about a month into the new training program.


In the case of metatarsal stress fractures, it’s especially important to recognise that a “new stress” on the bone is not limited just to increased mileage. Transitioning from doing mileage on the roads to doing intervals on the track in racing flats or spikes is another new stress on your metatarsal bones, for two reasons.


The obvious one is that spikes and racing flats tend to make you run with more of a forefoot strike, hence increasing the stress on your metatarsal bones.

Perhaps less obvious is simply the effect of speed. Even independent of footwear, high speed workouts also result in most people transitioning to more of a forefoot striking style, hence increasing metatarsal stress. So, even if your mileage stays the same, consider taking a “down week” from using spikes and flats every 3-4 weeks when ramping up track work.


HOW TO TREAT A METATARSAL STRESS FRACTURE:


None of this prevention does a whole lot of good for you right now if you’ve already got a metatarsal stress fracture. The good news is that metatarsal stress fractures tend to heal somewhat faster than other stress fractures, and in most cases, are “low risk”—they heal quite well, excepting the rare case of fifth metatarsal stress fractures. One review of 320 cases of stress fracture found that metatarsal stress fractures take an average of 7.9 weeks to heal, compared to 11.7 weeks for tibial stress fractures. In this study, "recovery" was defined as the time from diagnosis to return to pre-injury activity level (not the amount of time off from any running).


CONCLUSION:

If you’ve developed an aching pain or soreness on the top of your foot, you might have a metatarsal stress fracture. This injury can be easily distinguished from extensor tendonitis—the other main cause of top of foot pain—thanks to a few key symptoms.

Metatarsal stress fractures hurt (usually a lot) when you apply direct pressure to the injured area with your thumb. They tend to get worse as a run progresses, and they will be more painful on uphills and during barefoot walking or running. None of this is true for extensor tendonitis.


Whether you’ve suffered a metatarsal stress fracture or are looking to prevent one, the main risk factor that you can control is the level of stress in the metatarsal bones. Strong circumstantial evidence suggests that strengthening your toe flexor muscles is an excellent place to start, because toe flexor fatigue increases stress on the metatarsals.

Keeping your vitamin D and calcium intake high may reduce your risk as well by helping your body improve bone strength.

A more rigid running shoe that outsources some of the bending stress to your shoe's midsole might reduce stress on your metatarsals.

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