First of all, you’ve posted two different links to two different websites that were funded by Vibram USA to sell their hokey whatchamacallits.
SITE DISCLAIMER: The information provided is for educational purposes only, and is not a substitute for advice from a physician. Please see our User Agreement.
FUNDING DISCLAIMER: Research presented on this site was funded by Harvard University and, in part, by Vibram USA®.
Secondly, this is not a study on whether or not hell striking is better or worse than forefoot striking in elite athletes, which is the topic of this thread. This is a study of runners who run at least 20 kilometers a week, that's 12.5 miles per week. These are not runners, even the cultists posting on this thread run more than that. . The fact that the author, funded by Vibram, USA, has chosen Kenyan adolescents as subjects is clear. He’s attempting to co-op gravitas to his study, and for his sponsor. That link ties in neatly with his yarn about “human endurance running in the savannah, MILLIONS of years ago” , (factually incorrect) and modern Kenyan adolescents. At least the author stopped the hyperbole long enough to admit that Kenyan RUNERS wear riunning shoes and do not run barefoot. Ya think they might be on to something?
The study, the website, the “school” is all about marketing a new-age footwear product to the masses. It has nothing to do with competitive running, nor the topic of this thread.
The elephant in the living room is, why didn’t he study elites, and specifically, elite Kenyan runners while he was in Kenya?
He starts off with thisthe vast-majority, 75-80% of all endurance runners are heel strikers. I should have stopped reading at that point, but I continued.
He provides three videos of those non-runners who run 12 miles a week, running 4-6 m/s which shows that impact forces in all pretty much the same with the forefoot strikers having this highest peak impact values:
Barefoot/heelstrike = 2.37 x body weight
Shod/heelstrike = 2.37 x bodyweight
Barefoot/forefoot = 2.70 x bodyweight
No explanation why he didn’t study shod/forefoot runners? Perhaps he didn’t like the results? No explanation why the WIDE range of 4-6 meters per second running speed (4:28 to 6:42) , nor which runners or how many ran at which speeds in this study? Anyway, in his commentary he turns around and directly contradicts the evidence shown (of peak loading values) in the videos. Instead of addressing the obvious, that forefoot strikers have higher peak impact forces values than heel strikers, he shifts his emphasis to the RATE of the increase in force values. By itself, that’s a fine analysis, if it is valid and germane to the topic, but completely ignoring those contradictory (to his thesis) loading values seems a bit funny to me.
Now he goes on to speculate (not offer proof) that the rate of the increase in loading forces is “thought by many” to be the primary cause of injury, then he says “NOBODY KNOWS FOR SURE”. So what he did was juxtapose an hypothesis ("thought by many") right next to a fact ("nobody knows for sure") How many times have we seen this tactic in this thread?
I don’t even know why I even bother to write this far, but I’ll go ahead and summarize this article.
1) Published in a website that was funded by a new-age footwear company selling a gimmick to the masses at strip malls everywhere.
2) Study funded by the same new-age footwear company.
3) Subject of study were runners who have run 12.5 miles a week. None of them are elite, or even sub-elite runners.
4) Subjects filmed at running speeds varying for 4:28/mile to 6:42/mile. Study offered no information who or how many ran at what speeds, nor offered an explanation why the extreme range of speeds?
If Lieberman wants to make a ground breaking study he should study elite heel runners, elite forefoot runners, and elite midfoot runners, and all at speeds similar to the paces of their racing successes. All of them in shoes, then all of them barefoot.
Or at the bare minimum, the subjects in his study should have all been running the same pace. The subjects in his study should have all been running trials of with shoes and without shoes.