Triathlete Magazine senior tech editor Aaron Hersh points out some key oversights in a recent post on the “barefoot vs. shod running” argument.
Written by: Aaron Hersh
Ross Tucker of SportsScientists.com—an excellent blog-format website where he and Jonathan Dugas provide insightful physiological analysis on the world of endurance sports—recently wrote an article arguing that barefoot running or simulated barefoot running in shoes such as Vibram Five Fingers is theoretically better than running in a more typical shoe based on the following points:
1. The shock that the body absorbs upon striking the ground is reduced. Although the total amount of force the foot absorbs is the same, but the rate at which it absorbs it is slower and therefore the impact is less violent.
2. Barefoot running allows the body to use the calf and other support muscles to a greater degree.
3. Humans thrived for millennia by running to hunt for food without shoes and are built to meet the demands of distance running.
Tucker makes it clear that barefoot running may not be practical for many runners despite the sound theory.
The evidence and reasoning supporting these points overlooks a few critical elements of the “barefoot vs. shod running” argument, and we address these issues one by one. For the purposes of this article, I will use the term “barefoot running” to describe running in Vibrams or something similar to eliminate the problem of stepping on glass or other debris.
1. Barefoot running transmits a less violent shock to the runner at foot strike because it distributes the impact with the ground over more time.
Rebuttal: Barefoot running doesn’t reduce impact force, forefoot striking reduces impact force.
The argument that running barefoot reduces shock is largely based on the following three graphs, which show that running barefoot results in a softer, more gradual impact with the ground. The uphill slope at the start of each peak represents the impact loading rate, or the shock experienced by the runner at foot strike. A steeper slope means a more violent impact.
This first graph (below) shows the vertical impact force when heel striking in a running shoe.
The spike before each peak is typical of a heel striking gait and is even more dramatic when heel striking barefoot.
This second graph (below) shows the vertical impact force when running barefoot with a forefoot-striking gait.
When striking with the forefoot while barefoot, the initial spike is gone and the full load of 2.5 times the runner’s body weight is applied more slowly.
This third graph (below) shows that although running in shoes reduces the impact force during foot strike when heel running in shoes compared to heel running barefoot, forefoot striking while barefoot creates a much smaller initial impact force than the other two conditions.
Most runners new to barefoot running quickly learn to strike with their forefoot, so it seems logical that running barefoot would reduce injury when compared to running in shoes because this initial shock is so much less.
This chart is not only a comparison of barefoot to shod running, but it is also a comparison of forefoot to heel striking. To complete the chart, it needs a final data point of a forefoot striker in shoes. This argument promotes forefoot running, not barefoot running.
The dramatic change in initial impact force did not come when the subjects switched from shod to barefoot; it came when they switched gait pattern from heel striking to forefoot striking. There is no reason to believe forefoot striking in shoes would result in an impact force more similar to the “shoes heel” column than the “barefoot forefoot” column.
One of the studies cited declares that running in shoes promotes heel striking, so therefore forefoot striking in shoes isn’t a practical option. But the article then goes on to clarify that a prolonged adaption or break-in period is needed to run barefoot without excessive soreness or injury. So why not use that period to learn to strike somewhere other than the heel while wearing shoes? Shoe brands are now designing shoes specifically to facilitate fore- and mid-foot striking by building them with a smaller height differential between the toe and the heel. Although some shoes certainly can promote heel striking, there are plenty of alternatives that help facilitate mid- or forefoot striking.
2. Barefoot running allows the body to use the calf and other support muscles to a greater degree.
Rebuttal: Barefoot running forces the body to use the calf and other support muscles. This additional load could be a benefit while training, but why increase stress on the runner while racing or running as fast as possible in training?
Instead of relying on the shoe’s shock absorption characteristics to dissipate force, a barefoot runner is required to use muscular energy to support their body when it impacts the ground.
Barefoot forefoot runners enter the contact phase of their gait gently by using muscular force to slow their descent, starting at the ball of the foot. Cushioning the body entirely through its own structures is not free, however. It requires muscular power, mainly from the posterior tibial compartment. Running with external cushioning either from a shoe or a soft surface removes some of this burden because the heel is now able to contact the ground at a higher speed without getting injured. It removes the burden of eccentrically lowering the runner from initial forefoot contact through the lowest point of the stride. Supplying all the necessary cushioning puts massive additional stresses on the body compared to cushioned running, which could be one of the reasons why getting accustomed to barefoot running requires so much time.
These stresses certainly strengthen the body and might harden it to the demands of running barefoot or in shoes, but even after an acclimation period the body is still responsible for creating that cushioning for itself through muscular support of the foot. This costs energy.
Tucker wrote, “Running in shoes requires next to zero eccentric work in those (posterior tibial) muscles.” Eccentric work is a muscle exerting effort while being extended rather than contracting. This occurs, for example, in the calf muscles after contacting the ground while forefoot running. Eccentric muscle contractions are linked to muscular soreness and eventual breakdown.
Eliminating the eccentric work required by barefoot running relieves the runner of a burden. Habitually eliminating this stress can make a runner weak, but reducing the amount of eccentric contraction required by a runner might reduce his or her total muscular requirement and stress from a run. That sounds like a good thing on race day.
Training barefoot might have immense benefits to a runner’s strength and ability to withstand impact, but barefoot running on a hard surface might always be more metabolically expensive than running with external cushioning—either from a shoe or from soft ground—because runners must expend energy to cushion their body at foot strike.
The impact reduction from forefoot running could be an excellent way to reduce injuries caused by impact, but forgoing running shoes has other consequences, namely the elimination of energetically cheap cushioning that comes from shoes and perhaps an increased likelihood of injury to the tissues that provide this additional support.
Although this is speculative, perhaps barefoot runners select a true forefoot gait rather than a mid-foot gait because they need the additional cushioning that comes from softly landing on the forefoot. Shod runners with a similar stride might tend toward a mid-foot striking gait because the shoe is providing some of that additional cushioning for free.
3. Humans thrived for millennia by running without shoes to hunt for food.
Rebuttal: Persistence hunting proves our ability to run without shoes, not that humans are optimized when running without shoes, and addresses heat dissipation as much as running efficiency.
The evolutionary argument—that we are constructed to run without shoes—is frequently supported using the example of persistence hunters. Before the development of projectile weapons, hunters would chase animals on foot in the heat of the day. The animals could of course sprint much faster than the human hunters, but the hunters had superior endurance and could drive the swifter animals to exhaustion by pursuing them until they overheated and collapsed. Christopher McDougal discussed this at length in his book Born to Run, and anthropologists and other scientists have described the influence of persistence hunting on evolution.
If persistence hunters from before the days of projectile weapons somehow came upon a pair of modern running shoes, would they have failed to catch the animals they pursued? Persistence hunting is a comparison of the relative endurance capabilities of two different species and does nothing to highlight the differences between shod and barefoot running. It only proves that people can run long distances.
Although the fact that humans have been running for much longer than shoes have been around certainly proves that people are physically equipped to run without shoes, persistence hunting centers around heat dissipation in addition to endurance running ability. If an antelope or similar four-legged mammal had sufficient ability to cool itself, persistence hunting might not be effective.
What this means to you:
- Barefoot running might be more energetically expensive than cushioned running, regardless of injury risk.
- Forefoot striking, not barefoot running, reduces the shock experienced upon impact with the ground.
- Barefoot running puts massive additional stresses on the posterior tibial compartment (Achilles tendon and calf muscles) because it is working to cushion impact with the ground. This can lead to injury in runners that aren’t accustomed to it.
- This additional stress makes barefoot running a great training tool. It subjects the body to this increased load and introduces a new and highly specific type of strength training that most people have never experienced because typical running shoes prevent it.
- Some shoes are designed to help runners strike the ground with their mid-foot or forefoot, while others tend to promote heel striking. If you aspire to a mid- or forefoot striking gait, shoes with a low rise from the toe to the heel can help. Shoes such as the Saucony Kinvara, New Balance Road Minimus and the new Newton MV2 provide different levels of cushioning but all have very little or no lift in the heel. This type of shoe helps the runner strike forward on the foot, thereby preserving some of the softer landing experienced when barefoot running, without sacrificing the reduction in cost of cushioning and other benefits of traditional shoes.
About The Author:
Aaron Hersh is the Senior Tech Editor for Triathlete Magazine.