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
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.