What do Orthotics and shoes actually do? Looking at data from a professional runner



Often times in research we focus on norms.  We look at the average effect of different interventions and then apply them to everybody.  In this way, as a whole we get what the effects are for most people.  By doing this, sometimes we miss the individual effects.  So in today’s first blog of 2013, I want to share with you some data on the effects of running shoes on data with one  individual athlete, Jackie Areson, who runs professionally for Nike.

In this data, what we did was stick her on a treadmill running at the same speed for every trial and set up my poor man’s high speed video analysis system (Casio Exilim + free motion analysis software), and took side and back views of her running.  What I was looking at was a comparison of shoes impacts on her mechanics.  Using barefoot as the “normal” and comparing from there.  We looked at all sorts of different Nike shoes (because that’s her sponsor), her old shoes she trained in in college (Brooks Ravena) and then just for the heck of it, each shoe with custom orthotics and without custom orthotics (she does NOT wear them) to see the effects orthotics had on her mechanics.

 So what you'll find below is a chart comparing I’ve included pictures below for you guys to take a look at that give a good indicator of things and includes  a few other shoes not included in the chart (because remember, this data is analyzed the old fashioned way so it takes a while to analyze it all!).




Pronation Pronation Footstrike
Orthotics? change Change (deg) Degree    Ground Contact Flight Time Footstrike Heel-toe drop
Lunar Fly NO 7 10 93.6 0.214 0.114 whole 10mm
Lunar Fly YES 7 9 10mm
Katanas No 9 10 92 0.195 0.128 midfoot 4mm
Lunar Racers No 9 13 93.4 0.2 0.123 whole 7mm
Lunar Racers YES 9 11 98 0.209 0.119 Heel 7mm
Pegasus No 8 10 100.7 0.214 0.104 Heel 12mm
Pegasus yes 9 11 101.6 0.214 0.109 Heel 12mm
Vomeros Yes 10 12 96.5 0.204 0.114 heel 11mm
Barefoot No

93.8 0.195 0.119 forefoot 0mm









 Footstrike degree- 90deg= knee and ankle of foot are at 90deg angle. So greater the degree, means further out ankle is in front of knee at footstrike.
(Heel toe drop is using data from outside sources, not measured)


Pictures of shoes at footstrike- NO Orthotic on left.  Orthotic on right  (except for Nike free, Katana, and streak XC- NO Orthotics on those)




What did we find with Jackie. 
 1. Orthotics almost always switch to a more pronounced heel strike (probably for a few reasons- They add weight, bulk, and increase the heel to toe drop.

2. Orthotics don't decrease pronation really, and don't have a uniform effect across shoes.  They tend to change things in different degress.

3. Footstrike is greatly influenced by shoe type.  It's hard to pick out definite trends, but the less heel-toe drop the more likely she lands forefoot or mid/whole foot.  Additionally, the lighter the shoe the more so.  Interestingly (and the data isn't up there) but for some reason she lands more whole foot with the Brooks Ravena then with comparable shoes in terms of heel/toe drop and weight.  My guess is because of the high toe spring changes her loading/landing pattern (because at this period of time, she protected her past foot injuries by not "pushing off" her big toe.) Also, the contrast between flats and shoes is remarkable.

4.  Using the simple measure of ground contact time tells you how minimal a shoe is.  It's a kind of "duh, that's obvious" conclusion, but a simple measure of comparing barefoot ground contact time versus shoe GC might be a useful measure.  The difference (at the same speed) could give an indicator of how much the shoe "interferes".  So maybe a simple yet effective measure might be change in GC with each shoe?  (Just hypothesizing but how cool would it be to go to a shoe store and run barefoot, get a GC, then compare shoes effects on it, instead of doing pronation junk?)

5. Pronation- It varies.  And having junk in your shoe to stop it really didn't do much at all for Jackie. (and yes, pronation is natural, I just included in this analyse because it's easy to measure, everyone measures it, and I wanted to show the effects shoes had on it...)


Hopefully this data makes you think a little bit and gets you to see the individual differences that shoes create.

Anybody notice any other trends?  

11 comments:

  1. I did some similar analysis with a dozen runners at Bill Sand's lab at Colorado Mesa University.

    The biggest thing we saw is what you said: different shoes affect biomechanics in a big way for many runners.

    The biggest factors I identified had to do with heel height, and how much the sole flares out from the lateral side of the foot.

    If a heel is too high, even a midfoot striker can't avoid it.

    And if the sole extends out past the medial edge of the foot, the sole hits the ground before the foot is "ready" and, depending on the stiffness of the sole, can cause the foot to "flip" onto the ground, creating overly fast pronation.

    The biggest thing we realized, when seeing how different shoes affect gait, is that the way orthotics are usually fitted -- by having you stand barefoot on the ground (while immobile) -- has no relationship to how they work in the real-world.

    Now, some runners could practically put on a pair of bricks without any change to their gait. These tended to be the shorter distance (400-800m) runners who were forefoot strikers.

    And, FWIW, the only footwear that we saw that was essentially identical to barefoot was Xero Shoes (formerly Invisible Shoes).

    ReplyDelete
  2. Interesting observations Steve. Thanks for sharing.
    I'd be curious to see photos that include the degree of extension in the subject's knee in each case as the implications of a heel strike on a fully extended knee are obviously different than if the knee is slightly flexed. Do they differ at all?
    Look forward to your feedback,
    Matt.

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  3. Interesting data Steve, thanks for putting it out there. Individual analysis like this is really what's most critical for a given runner, and people who rely too much on published science as the one and only guide often fail to appreciate this.

    I personally find that I can't avoid the heel in a more traditional shoe and at this point am content to let my body figure out how it wants to run in each shoe. Echoing Steve Sashen's point above, lateral heel flare with a stiff sole seems to really torque the foot quickly into rapid pronation.

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  4. There is a fundamental flaw in your study. The subject knows what shoes she is putting on and this knowledge may change the way she strides. While double blind is the gold standard for such studies, yours has no one blind. This really limits any conclusion you can make.

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  5. Steve,

    This was an interesting post, thanks for sharing. In my experience, I have noticed that putting some type of landmark or reflective material at a pre-determined point (e.g., fifth metatarsal head) aids in the measurement of angles using the 'poor-man' approach to kinematic analysis. This is especially critical when the differences in angles are as small as a degree or two - which is imperceptible to the naked eye - and probably a lot smaller than the margin of error in 'eye-balling it.'

    During the study, how long did the athlete have to run in each different shoe before you began collecting data? The human body has a remarkable ability to adapt both short- and long-term to the environment/stresses we impose upon it. I am sure that many would agree that sometimes it can take as much as several miles before a runner gets used to a new pair of shoes. I wonder if the differences are as pronounced after a week of running with each different condition?

    Ultimately, what you show is that (among other variables) orthotics make a difference. But what are the implications of this difference? How does this difference compare to normal variability of a runner over the course of a run or a training program? Is this difference good, bad, or irrelevant?

    Cheers,

    Cory

    ReplyDelete
  6. Hi Steeve,
    Nice post.
    I think the drop is a criteria with a moderate influence compare to the protection that the orthotics and the shoes provide... often link with the stack (the "interference"). It's the reason why you see someone with a foot-ground angle up to 40degrees... even with only 8mm drop. When we worked on our formula to quantify how much the shoe change the biomechanics (how far we are from barefoot) we gave .25 to the stack and .15 for the drop. just my thought.
    Cheers

    ReplyDelete
  7. An additional thought:
    Adding orthotics to a shoe with a relatively soft insole does not provide support for the orthotic to work on (as is such with all shoes that you look on).

    For example: No matter how much support an orthotic is designed to give, if you stand on them on a mattress it'll be like they're not even there.

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  8. Anonymous5:40 PM

    Curious how/if this would change if the person was an excessive pronator rather than a neutral runner.

    ReplyDelete
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  11. Claudia said, very much effective comparison you have given in here and by notifying your given pictures I saw the effect of running shoes very nicely. So it's really great work and people will get a tremendous research from you as well. So keep going and do well in near future. Best of Luck:)

    ReplyDelete

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