Barefoot running

Shaky science for shoes and soles

Bare feet, Vibram five-fingers, racing flats or motion control shoes? By now almost every runner is aware of the increasingly heated debate over how much shoe cushion, heel-to-toe drop and structure are ideal. The medical, scientific and running communities comprise both die-hard barefoot and shod running advocates; yet presently, support for both sides of the argument stems largely from small-scale, unreliable studies at best, or anecdotal claims that bare or minimalist running will improve or impair performance, and cure or cause injuries. How then, is a runner to select footwear that’s optimal for performance and injury prevention? In their recent paper 1 published in Current Sports Medicine Reports, Doctors Allison Altman and Irene Davis attempt to settle some of this confusion. In this elegant review they discuss existing evidence both for and against barefoot running, based on recent research evaluating barefoot and shod running injuries and mechanics.

The Evolution Argument

An oft-cited argument for barefoot running is our evolutionary history. It is thought that many of our ancestors walked and ran, often for very long distances, with only the support of our bare feet, rendering modern humans well adapted to run shoeless. Humans had been running perfectly well for thousands of years without the modern running shoe, which didn’t appear until the 1960’s. Although these shoes were introduced to facilitate efficient and healthy running, only now are we beginning to systematically investigate and understand how they actually affect running biomechanics.

Shod Biomechanics and Injuries

Vertical ground reaction force for shod rear- (RFS), mid- (MFS) and forefoot (FFS) strike. Note the distinct impact force for the RFS. From Altman & Davis 2012.

Between 19-79% of runners become injured each year 2, and current estimates 3,4 indicate that the large majority of today’s runners are rearfoot strikers (75-89%), while the remainder demonstrate a midfoot (3-24%) or forefoot (1-2%) strike. A rearfoot strike, which is encouraged by the cushioned, elevated heels of conventional running shoes, are associated with a defined impact peak upon foot contact (see figure). Considering evidence that running injuries are 2.5 times more likely in rear- than forefoot strikers, it is feasible that the higher impact loading associated with rearfoot striking may be partly to blame for the pervasive tibial stress fractures, plantar fasciitis and patellofemoral pain that plague so many shod runners. In further support of a possible link between injury and footstrike patterns, it’s been shown that increased anterior compartment pressure related with excessive anterior loading can be alleviated by switching to a forefoot strike.

Barefoot Biomechanics and Injuries

Considering the biomechanical differences associated with footwear choice and the correlations between injuries and footstrike patterns, it is not surprising that distinct injury profiles are observed in runners depending on their footwear. Since the bare heel is not adapted to striking the ground while running, barefoot running encourages greater plantarflexion (towards to sole) and consequently a shift from rear- to forefoot striking. This forefoot strike adopted by most barefoot runners can reduce stride length and increase cadence. These subtle changes have been shown to minimize energy absorption by the knee and hip joints by lowering impact forces through eccentric loading in the calves. By redistrubuting impact forces in this way, a forefoot strike is thought to place greater strain on the achilles and increased load on the metatarsals. But surprisingly, pressure on metatarsals does not actually differ between barefoot and shod running, possibly because a barefoot strike can capitalize on the energy storage capacity of the arch.

It’s likely that other benefits of baring one’s feet, including increased mechanosensation, improved balance and ankle proprioception, may confer additional protection and injury prevention. A study 5 comparing runners in traditional and minimalist shoes (Nike Free) in fact reported increased vertical loading in the minimal shoe condition. Although this study was underpowered with only five subjects, their findings support the hypothesis that cushioning – even in a lightweight shoe – impairs sensory feedback in a potentially dangerous fashion.

Barefoot Bottom Line

With the abundance of unreliable anecdodatal “evidence” circulating around both sides of the barefoot running debate, a critical review of the existing scientific evidence to set the record straight has been long overdue. And although the research is still inconclusive, Altman and Davis do a respectable job exposing which claims we can trust, and what questions remain unanswered. Together, the evidence strongly supports two main findings:

1) Barefoot running can significantly alter the way we run by encouraging a midfoot or forefoot strike.

2) Distinct footstrike patterns are associated with different types and rates of injury.

What the existing research has yet to resolve, is what additional advantages, besides altering footstrike, barefoot running may provide. Or how best to transition from shod to barefoot, or whether individual differences may preclude some runners from safely running barefoot. The correlation between injury and footwear is still poorly characterized and the long-term effects of barefooting are essentially unknown.

Still confused about whether to bare your running soles? Take comfort in the knowledge that you are not alone, as even the “experts” are still hunting for answers. Until science catches up with the impassioned claims, your own self-experimentation might just be your most reliable guide.

References

    1. Altman AR & Davis IS. 2012. Barefoot Running: Biomechanics and Implications for Running Injuries. Curr Sports Med Rep 11:244–50.
    2. van Gent RN et al. 2007. Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. Br J Sports Med 41: 469–80.
    3. Hasewaga H et al. 2007. Foot strike patterns of runners at the 15-km point during an elite-level half marathon. J Strength Cond Res 21: 888–93.
    4. Larson P et al. 2011. Foot strike patterns of recreational and sub-elite runners in a long-distance road race. J Sports Sci 29: 1665–73.
    5. Willy R & Davis I. 2009. Kinematic and Kinetic Comparison of Running in Neutral Cushioned Shoe and a Minimal Shoe. American College of Sports Medicine Annual Meeting, Seattle, WA.

ResearchBlogging.org
Altman AR, & Davis IS (2012). Barefoot running: biomechanics and implications for running injuries. Current sports medicine reports, 11 (5), 244-50 PMID: 22965347

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2 thoughts on “Shaky science for shoes and soles

  1. Wow, marvelous blog layout! How long have you been blogging for? you made blogging look easy. The overall look of your web site is wonderful, as well as the content

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