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morendurff83
04-05-2010, 05:08 AM
The observation that forefoot strikers lack an impact transient has been made many times prior to Lieberman’s publication.
For example, in trying to explain the differences in the vertical ground reaction force (vGRF) transients between rearfoot and midfoot strikers during shod running, Cavanagh & LaFortune, J. Biomech, (1980) state: “…it is clear that a complete kinematic description of the movements of the body is required for a full understanding of the implications of these results.”
The shod vGRF data of Cavanagh and LaFortune look very similar to the vGRF data of Lieberman, et al. Perhaps the loading rate differences in Lieberman, et al are due to forefoot vs. rearfoot striking as well as shod vs. barefoot differences?
Lees, et al, Foot Ankle Int, (2005) investigated arch height to explain the vGRF transient in barefoot forefoot-contact running conclude that the arch index was “not the major factor in determining the way in which force is transmitted to the musculoskeletal system in forefoot running”.
Both of these publications provide biomechanical explanations for why different kinds of foot strikes lead to different impact transients. There are dozens of published papers focusing on vGRF patterns during running.
Although Lieberman, et al (2010) present no data on the weakness of the intrinsic muscles of the feet of habitually shod runners, in their paper the authors feel confident enough to write in the discussion:
“Furthermore, many running shoes have arch supports and stiffened soles that may lead to weaker foot muscles, reducing arch strength. This weakness contributes to excessive pronation and places greater demands on the plantar fascia, which may cause plantar fasciitis.”
I consider this statement to be highly speculative and not supported by the data generated from Lieberman’s paper or from other published literature This is important because of the current hype about barefoot running and the fact Lieberman’s group received partial funding from a shoe manufacturer to conduct this research. Nevertheless, this statement might be true—running shoes might cause the intrinsic muscle of the foot to become weaker. Their statement is an interesting hypothesis, but we do not yet have the data to support this highly speculative statement.
If I had reviewed this paper I would have required either a citation to back up Leiberman et al’s speculative statement about running shoes making feet weak or asked that the discussion be focused more closely on the data generated in their study. This is especially true considering the current popular infatuation with barefoot running. If this paper was submitted to a journal with editors and reviewers who possessed substantial expertise in evaluating biomechanical data, perhaps Lieberman’s data would have received more expert scrutiny than it apparently received at Nature.
The well-understood molecular signaling cascades support the possibility that performing an endurance exercise to gain strength is a fool’s errand.


Michael Orendurff
Division Director
Movement Science Laboratory
Texas Scottish Rite Hospital for Children
Dallas



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