Achilles tendonitis: Lift the heel, right? It does not appear so.

There was a recent article in one of our favorite journals, Lower Extremity Review which reviewed and expanded upon another study from Medicine and Science in Sports and Exercise titled “Running shoes increase achilles tendon load in walking: an acoustic propagation study.” We discussed some perspectives of this topic in one of our recent podcasts.
The article discusses a new technique (1,2) for looking at tensile loads in the achilles and looks at 12 symptom free individuals on a treadmill barefoot and in a shoe with a 10 mm drop (heel is 10mm higher than the forefoot) and found:

“Footwear resulted in a significant increase in step length, stance duration, and peak vertical ground reaction force compared with barefoot walking. Peak acoustic velocity in the Achilles tendon (P1, P2) was significantly higher with running shoes.”(1)

According to LER: “The researchers also found changes in basic gait parameters associated with walking in running shoes versus barefoot, which the author Wearing said may help explain the increased tendon load with shoes. Shoes increased mean ankle plantar flexion by 4° during quiet stance as measured by electrogoniometry. When walking with shoes, participants adopted a lower step frequency but greater step length, period of double support, peak vertical ground reaction force, and loading rate than when walking barefoot. The researchers also noted that participants’ stance phase was relatively longer (4%) during shod walking than during barefoot walking.” (3)

Of course, our big question is why?

Why would an increase in step length result in increased tension?

Perhaps, as the force that the heel would hit the ground would be increased because of a longer acceleration time (F=ma), and it so happens this is what they found. The friction of the heel striking the ground would accelerate anterior translation of the talus, which plantar flexes, everts and abducts, accelerating pronation. The medial gastroc would be called into play to slow calcaneal eversion and this would indeed increase achilles tension.

Or perhaps it’s the fact that

the foot will strike in slight greater plantarflexion

(at least 4 degrees according to the study) and this results in an immediate greater load to the Achilles tendon.  Go ahead and try this while walking even if you’re barefoot. Walk across the floor and strike more on your forefoot. You will notice that you have an increased load in the tricep surae group.

Does this slight plantarflexion of the ankle contribute to greater eccentric load during stance phase?

This would certainly activate 1a afferent muscle spindles which would increase tensile stresses in the achilles tendon.

This seems to fly directly in the face of the findings of Sinclair (4) who investigated knee and ankle loading in barefoot and barefoot inspired footwear and found increased achilles loading in both compared to “conventional shoes”.

Of course this also begs the question of what type of shoes were they wearing? High top or low top shoes and were the shoes tied or not? High top shoes seem to reduce Achilles tension more so than low top shoes, especially if they are tied (5).

Whatever the reason, this questions the use of putting a lift or a higher heeled shoe underneath the foot of people that have Achilles tendinitis.  Once again what seemed to make biomechanical sense is trumped by science.

We think training people to have greater amounts of hip extension as well as ankle dorsiflexion,  as well as appropriate foot and lower extremity biomechanics with the requisite  skill, endurance and strength is a much better way to treat Achilles tendonitis regardless of whether they’re wearing footwear or not.

Dr. Ivo Waerlop, one of The Gait Guys

References:

1. Wearing SC, Reed LF, Hooper SL, et al. Running shoes increase Achilles tendon load in walking: An acoustic propagation study. Med Sci Sports Exerc 2014;46(8):1604-1609.  http://www.ncbi.nlm.nih.gov/pubmed/24500535
2. Reed LF, Urry SR, Wearing SC. Reliability of spatiotemporal and kinetic gait parameters determined by a new instrumented treadmill system. BMC Musculoskelet Disord 2013;14:249.
3. Black, Hank. Achilles oddity: Heeled shoes may boost load during gait. In the Moment:Rehabilitation   LER Sept 2014  http://lermagazine.com/news/in-the-moment-rehabilitation/achilles-oddity-heeled-shoes-may-boost-load-during-gait
4. Sinclair J. Effects of barefoot and barefoot inspired footwear on knee and ankle loading during running. Clin Biomech (Bristol, Avon). 2014 Apr;29(4):395-9. doi: 10.1016/j.clinbiomech.2014.02.004. Epub 2014 Feb 23.
5. Rowson S1, McNally C, Duma SM. Can footwear affect achilles tendon loading? Clin J Sport Med. 2010 Sep;20(5):344-9. doi: 10.1097/JSM.0b013e3181ed7e50.

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