Mileage and Stress Fractures

The break in my right foot preceded by a large increase in mileage is proof enough for me.

There is tons of evidence that increased repetitive stress applied to bone during increases in mileage can lead to stress fractures. Bone is a very plastic, adaptable substance and over time changes form in response to any loads applied to it. Simply put, bone responds to increased stress (mileage increases) by temporarily weakening, then rebuilding stronger. With normal training loads, bone adapts and repairs at a rate fast enough to keep up with the loads applied to it. If you suddenly increase mileage (and thus stress applied to the bone) more weakening occurs and bone has less time to remodel. This can lead to micro fractures or a stress reaction, and if you continue with the same training loads and don't allow the body time to recover it may eventually lead to a full blown stress fracture.

Stress fractures are fun? wrote:

There is tons of evidence that increased repetitive stress applied to bone during increases in mileage can lead to stress fractures..

OK where is it?

When you increase your mileage too quickly, your muscles can't adapt to the repetitive stress quickly enough and become fatigued. The muscles are then unable to absorb as much shock under fatigue, and whatever energy transferred to your leg upon foot landing that is not absorbed by muscle will be distributed to the bones.

http://sportsmedicine.about.com/cs/foot_facts/a/foot4.htm

http://www.peoples-health.com/stress_fractures.htm

Here are a couple statements I found

"Training variables in runners commonly predispose to stress fractures. An increase in frequency, duration, or intensity of runs is often cited as a primary risk factor." Harrast 2010

"Failure to schedule rest days after higher intensity runs can also contribute to overuse injury risk." Milgrom 2003

All are peer reviewed papers published in scientific journals

Can a general lack of muscle lead to stress fractures? Say a runner who for whatever reason is just not prone to putting on muscle but is normal-sized, not sickly skinny and probably carries a decent amount of body fat?

Stress fractures are fun? wrote:

Here are a couple statements I found

"Training variables in runners commonly predispose to stress fractures. An increase in frequency, duration, or intensity of runs is often cited as a primary risk factor." Harrast 2010

"Failure to schedule rest days after higher intensity runs can also contribute to overuse injury risk." Milgrom 2003

All are peer reviewed papers published in scientific journals

Both of those sound like the authors opinions, not fact.

I've had two stress fractures and nearly gotten a third (or so maybe that means I did get a third, but it was minor). Each case is unique, but I think investigating them individually can yield important answers to an athlete.

1) I didn't run many miles in the off-season and tried to make up for it when the season started. I ran more miles than my body was prepared for and with more intensity. One day I was racing on hard dirt in spikes and my foot just refused to be elastic when getting slammed down so hard. Fracture. (Metatarsal on index toe stress fracture.)

2) I was enjoying a relatively good period of active rest in the summer and I was at the beach. I sprinted toward the ocean and fractured something before I even made it to the water's edge. This was not so much to do with impact, but the flexibility I was asking my foot to have propelling me through sand. (Some little bone under the lateral side of my foot.)

3) I ran a marathon in a somewhat soft shoe. The balls of my feet pressed into the soft insole and over the course of 26.2 miles my metatarsals were asked to flex a lot. I got through it okay, but felt tenderness there for a few weeks after at toe-off. (Metatarsal on middle toe nearly victim to a stress fracture.)

So, look at your cases and figure it out. For me, I know my metatarsals do okay in some sort of proportional continuum where firm midsole on grass is equal to semi-soft midsole on road and crossing any of the ingredients could lead to disaster.

I think it's erroneous to say high mileage is a primary factor. The problem occurs when I subject myself to a single or repetitive stress that my body just can't handle. Why my body or your body can't handle it is unique. For me it was once the case that my body was weak from overtraining, once probably weak from undertraining, and once just a bad choice of shoe for a road marathon.

As for "What actually causes the set backs occuring with high volumes of training?" What proof can you show me that runners at 30mpw suffer fewer injuries than runners at 100mpw? I'm constantly hearing BS from casual runners about what's holding them back at 30mpw when all the 100mpw people are banging these things out like pros.

When I had a stress fracture it was after a large increase in mileage but I would like to define "large increase in mileage" for me because I feel like people get it wrong. When I had a stress fracture my sophomore year of high school, it followed an increase in mileage from 40 miles per week to 100 miles per week. I heard about guys like Ritz doing 100 mile weeks and figured that must be the key to getting faster. For the record, I still think that's the key to getting faster but I just went about it the wrong way. But I read a lot of people saying that an increase from 80 to 100 is going to give you a stress fracture. I think that's total bullshit. It takes an extreme increase to produce a fracture caused by impact alone.

The only stress fracture I ever had came at 35-45 miles per week, high intensity. In the 25+ years since, I've had months averaging 3 times that and never had another.

If you are pounding the hell out of your legs, it doesn't take much mileage to get a stress fracture. If you save the intensity for the hard days and dont have terrible form, it seems to take a whole lot more. I haven't found out how much yet.

Question for those more knowledgeable:Based on this evidence, does it follow that the more muscular a runner is, the more shock they are able to absorb and less likely they are to sustain stress fractures who have significantly less muscle in their body comp?I ask because many of the runners that I know who struggle with stress fractures are almost always the ones that look like they are well under a healthy race weight. I mean, there is that "lean wolf" look, and then there is the "dying bird" look. Wetmore's quote in Running with the Buffs, that a good runner looks like "a skeleton with a condom pulled over it", has always seemed just a little extreme to me.Thoughts? Also, just want to say that this explanation makes a lot of sense to me. Based on the links, it seems that a lack of recovery is as much to blame for stress fractures as intensity and mileage. Take a high-mileage runner who is always pushing their redline and running too fast on their easy days, and you have a recipe for disaster.

Knows Nothing wrote:

When you increase your mileage too quickly, your muscles can't adapt to the repetitive stress quickly enough and become fatigued. The muscles are then unable to absorb as much shock under fatigue, and whatever energy transferred to your leg upon foot landing that is not absorbed by muscle will be distributed to the bones.

http://sportsmedicine.about.com/cs/foot_facts/a/foot4.htmhttp://www.peoples-health.com/stress_fractures.htm