Decreasing vertical impact loads via increasing ankle loads in Chi Runners

Hot on the heels of the systematic review last week that confirmed the adage that you can’t decrease the load in one tissue without increasing it in another and that different running techniques load different tissues differently, we have another study:

A Comparison of Negative Joint Work and Vertical Ground Reaction Force Loading Rates between Chi Runners and Rearfoot Striking Runners
Donald Lee Goss & Michael T. Gross
J Orthop Sports Phys Ther, Epub 9 September 2013
Study Design
To compare lower extremity negative joint work and vertical ground reaction force loading rates between rearfoot striking (RS) and Chi runners.
Alternative running styles such as Chi running have become a popular alternative to RS running. Proponents assert this running style reduces knee joint loading and ground reaction force loading rates.
Twenty-two RS and 12 Chi runners ran for 5 minutes at a self-selected speed on an instrumented treadmill. A 3D motion analysis system was used to obtain kinematic data. Average vertical ground reaction force loading rate (AVLR) and negative work of the ankle dorsiflexors (ADNW), ankle plantar flexors (APNW), and knee extensors (KENW) were computed during the stance phase. Groups were compared using a 1-way analysis of covariance (ANCOVA) for each variable, using running speed and age as covariates.
On average, RS runners demonstrated greater KENW (RS = −.332 J/BH*BW, Chi = −.144 J/BH*BW, p < 0.001), while Chi runners demonstrated more APNW (Chi = − .467 J/BH*BW, RS = −.315 J/BH*BW, p < 0.001). RS runners demonstrated greater AVLR’s than Chi runners (RS = 68.6 BW/s, Chi = 43.1 BW/s, p < 0.001).
Chi running may reduce vertical loading rates and knee extensor work, but may increase work of the ankle plantarflexors.

This study is better than the previous one I reported on that involved Chi runners (that despite having only 9 subjects got the Chi running community excited; yet they somehow manage to have a problem with the sample size of other studies that they don’t like the results of! … go figure). The above study had 23 rearfoot strikers and 12 Chi runners, which is better. It was on a treadmill, so the results have to be interpreted in that context.

The results of the study pretty much confirm what all the other studies are showing that choose to look at this topic: you can decrease the impact loads by changing to midfoot or forefoot strike, but only at the cost of increasing the loads at the ankle. Its six of one and half a dozen of the other and each load pattern will have a different injury risk profile associated with it.

The change in knee extensor work is also consistent with all the previous studies that looked at this (eg: Increasing cadence and patellofemoral forces & Barefoot vs Shod and patellofemoral joint stresses). However, you are only going to get this reduction in knee forces, via the increase in ankle forces. This might be a good thing if you are at risk for patellofemoral pain syndrome (runners knee) and a bad thing if you are at risk for Achilles tendinopathy or posterior tibial tendonitis.

This is also based on the premise that impact loads are actually a risk factor for injury in the first place and the data on that is hardly compelling!

As always, I go where the evidence takes me until convinced otherwise, and this evidence tells me that Chi running INCREASES the loads in the ankle and DECREASES the impact loads (which is only important if impact loads are even a risk factor for injury!).

BTW, I have just done a Chi running course; wait with baited breath for that report. It will be fun.

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4 Responses to Decreasing vertical impact loads via increasing ankle loads in Chi Runners

  1. Christian September 14, 2013 at 6:06 am #

    Great appraisal Craig. I think you summed it up well by matching the loading parameters to each inividual case at hand, rather than just assuming there is a one size fits all approach.

    Whilst there’s no compelling evidence for this, what’s your thoughts on potentially certain tissue being able to physiologically withstand a set load more than others.

    It seems all the craze at the moment, particularly in physio realms
    to offload and then once symptoms have been moderated, strengthen tissue to withstand great force. My concern with this is if the underlying reasoning betond and strength deficit is not identified and if that tissue is not capable of physiologically withstanding such load regardless of adaptation to strength work, are we really doing anything?

    • Craig Payne September 14, 2013 at 6:27 am #

      There is no doubt the tissues can be adapted, but it takes time, so it is not a short term measure for a runner in pain with an injury. Having said that, in some people the magnitude of the forces are so high that they just can not adapt (or if they can, we don’t have a long term to do so or the compliance is not there).

      I still getting my head around an article coming up to explain this some more (and also explain the inter-subject variability we seeing in the running economy), but briefly, consider these two thought experiments:

      1) In the heel striking runner with a more medially located STJ axis, the post tib muscle is going to be working 2,3, or more times harder than ‘normal’ due to the shorter lever arm. If for, whatever reason they should go to midfoot or forefoot striking (maybe to increase the cadence for a knee problem), as the post tib tend passes behind the ankle joint axis, its now going to have to work 6,7 or more times harder than ‘normal’. So we have the situation that midfoot or forefoot striking in this person is possibly going to help the knee, but that load in the post tib tendon is not sustainable and is probably not going to be adapted to and it was probably dangerous advice to get them midfoot striking! Now, if they had a relatively average STJ axis position, the transition away from heel striking will increase the load in the post tib tendon, but not by much and is sustainable and can be adapted to.

      2) We know the length of the calcaneus varies from person to person, so this means that the lever arm from the achilles insertion to the ankle joint axis will vary. Those with a longer calcaneus should find it easier to get up on the forefoot without much effort from the calf muscles –> easy to adapt to (it would be interesting to see how many ‘natural’ forefoot strikers actually have a longer calcaneus). Those with a short calcaneus are in a different position: to get up off the heel onto the midfoot or forefoot is going to require considerably more effort –> massively increased load in the achilles tendon that may not be able to adapt to that magnitude of load…… (there is a bit of a problem with this thought experiment due to elastic energy storage and return from the achilles means that the short lever arm may be more advantageous! – a couple of studies from evolutionary biology suggest that this may be the case.)

      Does that make sense?

      I am getting increasingly concerned about the increasingly blanket one size fits all change to running form for this, when things like joint axes positional variations are not taken into account before the advice is given.

      We learning and understanding more about this as time goes on.

  2. Matthew Thomas September 15, 2013 at 3:26 am #

    Wasn’t this type of issue addressed over ten years ago (2002) with regard to the Pose technique (hence implications also apply to Chi) study conducted by Professor Tim Noakes, which also included Dr Ross Tucker & Dr Jonathan Dugas (aka “The Science Of Sport” guys). They then wrote about their experience 5 years later (2007) in a series on running technique (on their Science Of Sport blog) where I believe Romanov et al liked the results/implication for the knee but didn’t like the results/implication for the Calf/Achilles… of which the potentially adverse Calf/Achilles implications weren’t published!

    This Science Of Sport article discusses the issue:

    “One small problem though…that eccentric loading doesn’t just disappear, it goes somewhere else…

    … Because what happened next was never going to be published in a scientific journal by the advocates for the technique, and would certainly not be reported on the website alongside the claim of reduced work on the knee! For what happened is that of the twenty runners who were trained, more than half broke down with calf muscle injury, Achilles tendon strains and other injuries of the feet! Let me elaborate…”

    🙂 Don’t you love objective science 🙂

    Which I suppose then inspired the following blog:
    Pose Running reduces running economy…the missing study:


  3. Bob Budding September 15, 2013 at 1:04 pm #

    Interesting research. Thanks for pointing it out and for the commentary. The runner-selected speed, however, may be problematic. It seems that it would be better to match speed, cadence, and weight when making comparisons across individual runner. Difficult to do with small sample sizes, of course.

    I’ve been thinking about the claim that we evolved running barefoot. This is, of course, true. But we;re much bigger and heavier now than were our ancestors. So a forefoot strike that may have worked perfectly well for someone 5 feet tall and 100 lbs may not be optimal for a 200 lbs modern runner.

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