One of the key reasons often suggested for transisitioning to a barefoot running technique is to reduce the impacts loads, which is only an important issue if you actually believe there is even a problem with impact loads and running. I previously reported a study that showed that tibial strain was actually greater when barefoot running vs shod running. Now we have another study that looked at similar parameters:
Influence of barefoot, barefoot inspired and conventional shoes on tibial accelerations and loading kinetics during running in natural rearfoot strikers
Comparative Exercise Physiology; in press
J. Sinclair, P.J. Taylor, S. Andrews
Running barefoot and in footwear designed to mimic barefoot locomotion, has received considerable attention in footwear research. This study examined the differences in impact force and tibial acceleration parameters. Ten male participants completed 10 trials when running barefoot, in vibram five-fingers and in conventional footwear at three locomotion velocities: walk, jog and run (1.25, 3.5 and 5.0 m/s, respectively). Impact force and tibial acceleration parameters were synchronously obtained and contrasted between footwear and velocities using 3 (footwear) × 3 (velocity) repeated measures ANOVA’s. Significant main effects were obtained for both footwear and velocity which suggest that barefoot running at higher velocities is associated with increases in impact loading magnitude. This leads to the conclusion that barefoot locomotion may be associated with increased risk of injury regardless of running velocity and that more specifically running barefoot at higher velocities should be undertaken with caution
I have to admit, that I was a little bored when I read the abstract. It was the ‘been there done that’ kind of response as it appeared to confirm what was previously reported (which is great and shows how science works) and just seems to add the added dimension of velocity, but abstracts don’t always tell the full story (see this eg) and the last sentence of “This leads to the conclusion that barefoot locomotion may be associated with increased risk of injury regardless of running velocity and that more specifically running barefoot at higher velocities should be undertaken with caution” gnawed at me enough to motivate a closer look at the full publication. I never initially read a full publication from start to finish, I tend to jump around all over the place looking at why they did it, what and how they did it, what they found, what they think it means and then the radar detector goes up to appraise all that properly. In this paper, I first jumped to this paragraph in the discussion as it got my attention:
This study also provides additional information to support the notion that footwear can significantly influence the vertical load imposed on the lower extremities during running (Sinclair et al., 2010, 2013a). The results showed that the conventional shoes were associated with lower impact parameters than running barefoot and in the vibram five-fingers. This supports the observations by Sinclair et al. (2013a), De Wit et al. (2000) and Hamill et al. (2011) who also found increases in impact magnitude in barefoot/vibram five-fingers. This leads to the notion that barefoot running barefoot and in vibram five-fingers may be linked to the development of injury in recreational runners. This finding opposes those from analyses that have utilised habitual barefoot runners (Hatala et al., 2013; Squadrone et al., 2009), thus providing support to the Sinclair et al. (2013a) notion that running kinetics during barefoot locomotion are influenced by the participants barefoot running experience. However, given the magnitude of the differences between conventional and barefoot locomotion leads the authors from the current study to propose that barefoot running does not serve to attenuate impact loading in runners who utilise a natural rearfoot strike pattern.
Does the data support that strong a conclusion?
Why they did it?
“The aim of the current investigation was to examine the influence on barefoot, conventional and barefoot inspired footwear at three different velocities”
What and how they did it?
They had the participants run in barefoot, in Vibram FiveFingers and in the Saucony ProGrid Guide 2 while using an accelerometer attached to the tibia at 3 different velocities (walking, jogging, running).
What they found?
Impact peak: Lower for the Saucony’s than barefoot and Vibrams; impacts were greater in all conditions for faster velocities
Time to impact peak: Greater for the Saucony’s than barefoot and Vibrams; greater in all conditions for faster velocities
Tibial accelerations: Lower for the Saucony’s than barefoot and Vibrams; interestingly, the tibial accelerations were also lower in the Vibrams compared to barefoot (this confirms other work showing differences between barefoot and minimalist shoes)
What do they think it means?
See the paragraph I quoted above.
What do I think:
- all the methodology, data collection validity and reliability as well as the analysis looks sound to me.
- this was an acute intervention; not habituated to the footwear conditions, so may or may not get the same results if the participants were given months to habituate to the barefoot and Vibrams (see this habituation study).
- nothing is reported on changes in running form (ie heel vs forefoot strike in the different conditions); they only used rearfoot stikers and nothing is known if any of them used a forefoot strike pattern when barefoot or in the Vibrams. I would have thought that this was a crucial point.
So where does this leave us:
This leads to the conclusion that barefoot locomotion may be associated with increased risk of injury
nothing is reported on changes in running form (ie heel vs forefoot strike in the different conditions); they only used rearfoot strikers and nothing is known if any of them used a forefoot strike pattern when barefoot or in the Vibrams. I would have thought that this was a crucial point
As always, I go where the evidence takes me until convinced otherwise, and I guess the applicability of this research depends on how much weight you want to give what I said vs how much weight you want to give to the strength of their conclusion. I am sitting on the fence.
J. Sinclair, P.J. Taylor, S. Andrews (2013). Influence of barefoot, barefoot inspired and conventional shoes on tibial accelerations and loading kinetics during running in natural rearfoot strikers Comparative Exercise Physiology DOI: 10.3920/CEP13023