This is a great question, and one that I asked Casey when I first suggested
the idea of a post on stress fractures to her. After she explained it to me,
I tried to boil it down in a reply to her to make sure I had things right.
This is the way I interpreted what she was saying:

“So, take an overstriding runner with a big heel strike and a nearly locked
knee on contact (which modern shoes allow and perhaps even encourage). What
you’re saying is that it’s not so much the initial impact that is the
problem, but rather how the initial positioning of the leg sets things up in
a negative way for the much larger forces at midstance. In other words, it’s
things that happen downstream from the initial long stride and extended leg
that are the big problem, but you can correct these indirectly by shortening
stride. This then is the benefit for many who run barefoot/minimalist – they
shorten their stride in such a way that they are better set to handle the
higher forces at mid-stance. Am I following correctly?”

Her response was “exactly!”

For a tibial stress fracture, such as what Irene Davis was talking about, I
can’t help but believe that impact shock plays a role. But, what Davis was
saying was that they correlated impact loading rate with a higher incidence
of injury. This is correlation, not causation. So, it could just be that a
higher loading rate is in turn highly correlated with something bad that
occurs at midstance, and the latter might be the real problem. This is the
difficulty of coming to firm conlusions based on correlation studies.

In either case though. shortening stride seem to mitigate the problem to
some degree, which is really the important thing after all.

If I had to bet, I’d guess that both impact shock and midstance forces have
the potential to cause injuries, but the injuries would probably be of
different types and in different spots.

Pete

i’m almost speechless, but not entirely

the feet and hands have a TON of muscles to be used and built up, 
the running gait with shoes is NOT deliberate, it is attempting it as it naturally would, but the amount of cushioning and drop causes a change

it’s just like how i think that if we wore gloves all the time, our hands would get weak, and our touch would be changed

just quit trolling and get outta here

Sorry bud, humans catch prey not by speed, but by endurance.  If you can keep, say, a deer at a gallop for a little while, it cannot sweat or cool during running, and will collapse eventually.  Please do your research next time, or don’t participate in this blog.  This blog is so good because of the level of intelligence by it’s readers.  We can have intelligent debates because we have done our research.  Pete takes the time to put truthful information in his blog, so the least you can do is become slightly informed.

By the way: Were you running in cleats when playing football?  That might be the reason why you are crippled now.

Also, i’m a teenager in high school.
David

Pete,

The real “a ha” moment for me came from a comprehensive
analysis of what I was seeing clinically with what I was observing in the
laboratory, combining force plate with motion analysis data (which remarkably
had never been done before). The peak stresses and strains across
virtually all common injury sites do not occur at impact but rather when the
foot is fully planted around the time of midstance. I know this is a difficult
concept for us to put our arms around as we all have been conditioned to think
that impact transients are what cause injury (e.g. this concept is what the entire shoe
industry has been based on). But in fact, the real stresses through common injury sites are determined by
measuring the body weight force in relationship to the position of the bones
and joints. Not only is the body weight force far more substantial around
midstance, the position of that force in relationship to our bones and joints
dictates to a tee where we get injuries, which are either compressive or
tensile in nature. E.g., for the tibia, only at midstance is there any substantial
compressive stress through the tibia and at that instant, the compressive
stresses are far greater on the medial compared to the lateral aspect of the
tibia. This is why we predominantly see tibial fractures on the medial rather
than the lateral side of the bone. The same type analysis explains why we
develop knee osteoarthritis on the medial, not lateral, side of the knee.

I know this all goes very much against what we’ve always
believed. Fortunately, when considering running form or running barefoot, per Mark’s point
below, I think the distinction between impact and midstance is a rather moot
point since the act of trying to hit the ground softly indirectly reduces the
peak stresses at midstance. But the distinction was pivotal from my end in
re-thinking a shoe midsole that could actually minimize (rather than increase!)
these stresses.

Casey

Re: Goatlips’ comments:  they made my day.  I can only equate him to George on Seinfeld.  He is way off base with his comments and tone, yet seemingly completely convinced that we are all complete morons.   Reading that actually made me even more sure that my move to running minimalism was the right one for me.

While reading his post, I was imagining the corporate heads of Nike, Asics, Reebok, etc all composing those comments via a conference call with their lawyers and an otherwise out of work ad copywriter.

This post is too stupid to be believable. It looks like an obvious troll to me.

I’ve not read the books or even the internet debates (or watched these vids, LOL), but my view is:

1. You can’t turn back human evolution – or improve it with a shoe, to any degree greater than they could 20yrs ago/at all. Anyone who thinks otherwise is naive. Feet are like hands – they barely change from training – they have virtually zero muscle or strength to develop.

2. No shoe can really change your running gait – you’d have to do it deliberately…until you get tired a revert to type. And changing from your natural gait would probably do more harm than good anyway. Most running injuries are RSIs, which can be kept at bay with a proper, regular, stretching regime – not a quick touch of your toes before a run (a proper regime would actually mean NO stretching before a run – stretched musles are less energetic).

3. Obviously, anyone who’s seen Oscar Pistorius run knows, for speed, trainers should be riged – to give you something to spring off, at the toe (your toes will NEVER be strong enough to do this naked!). And, to prevent injury, greater cushioning helps prevent bone/joint/spine wear. Perhaps if we ran barefoot we’d run softer – but only because of fear of treading on stones/glass/thorns/a glass marble/a half-eaten dog bone! But cushioning your foot strike with only your bare foot would cause metatarsals to eventually stress fracture – I rather let my big bone bare the brunt and not suffer a stubbed toe every 5 minutes.

4. You’re extremely unlikely to improve at anything if you try to reinvent your natural technique. i.e. You’re almost certainly running in the most efficient style for your body/proportions/weight/spine/feet/physiology/muscles/muscle attachment sites, etc, even if you run badly. The best sportmen always keep the same technique until they retire.

5. Some human feet and legs have evolved to become weak and puny. Some people are still robust. But in general, humans have evolved to need shoes even more than they need clothes! We’ve been wearing shoes for c.40,000 years!

6. Humans aren’t meant to run. Pound for pound we are the worst in the whole animal kingdom! We are slow and unfit, get hernias and injured when we run – that’s just the way it is – get over it/yourself. We have 2 legs. If we’d evolved to run we’d still have 4 legs and paws, and go around sniffing each others arses.

…Of course, none of the barefoot running idiots can have their topsy-turvy theories disproved because all people are different and therefore their ‘scientific’ delusions can’t be tested – which is probably a key design built in to their argument. 

…I suppose some self-righteous bigot is going to make a cry-baby response numbered 1~6 now. But I won’t be reading it, I’m too bigotted to my own (correct) opinions….LOLlololol:

I thought the same. It gets better. Seems maybe just an audience member filmed it.

Get over yourself buddy, it ain’t personal against you.

LOL.  Fair point.  You’ll get there, I’m sure. ;)