Friday, 23 November 2012

Feet Vs Shoes

Barefoot debacle!


Barefoot Running

This is such a big topic and has been one of the hottest in running over the last few years. It is also a very emotive topic with many people hell-bent, one way or the other. I will state for the record that I don’t fall one way or the other, in fact there may be cases for both. I will do my best in the space and time that I have to cover some of the major aspects and try to give a few different practical points while giving it some justice. I will cover some of the research and look at the aspects of injury.

Barefoot running is not new, whether you look at it from an evolutionary point of view or a literature point of view. In fact the opposite may be said. Shoes (as we know them) have only been around for the last 50 years or so, however, the last 30 years and more recently, the last decade has seen huge advances in shoe technology. The question must be asked ‘what are they based on – is there evidence for them?’ If there is no evidence for shoes, do we ditch them and just go barefoot? Or if there is evidence for them, which shoes are best?

Barefoot running is enjoying the limelight at the moment, slowly gaining popularity with a surge at about the same time as the book ‘Born to Run’ (by Christopher McDougall) travelled through distance running circles. This was followed shortly after by Dan Lieberman who published a study in Nature looking at shod (shoes) versus unshod (no shoes) running and foot strike characteristics. He found some interesting (probably not new) foot strike and landing positions.

The shoe companies saw this coming and quickly responded with barefoot running shoes – these are marketed as enjoying the barefoot benefits without the risk of acute puncture injuries. So the question must be asked “do the shoe companies believe in their current shoe technology or do they simply respond to market demand?”

We must consider the reason for wearing shoes. Is it to reduce injury? Is it for performance? Is it for comfort? Is it for trend? Certainly the big debate seems to be around injury rates yet the reasons for wearing shoes are multifactorial. This is not to dismiss the fact that they probably were designed initially to reduce injury. Here we are 30 years on debating on the design, implications and perhaps the viability of the humble running shoe!

Before we jump into looking at either, let’s have a quick recap on running and motor patterning, as this really does relate to this topic and impact on foot strike positions.

Let me state for the record, running is a skill and not simply a skill that we all possess at the same level. It is also one of the few sports where technique seems to be left in the dark. Very few coaches/athletes, even at the top level, regard technique as a major factor in sports performance or injury profile (sprinting, I must say, is quite different). Running like many sports needs to be taught and refined. Good efficient running technique doesn’t happen by accident. Many believe it’s an innate skill and something that just develops over time. There is varying abilities and skill levels. Quite simply there are responders and non-responders

Running is a complex motor pattern generated by the central nervous system. Because distance runners generate similar patterns on each stride they can re-enforce poor motor patterns pretty quickly! What we really need to consider is whether running bare foot changes these poor patterns and if so, does it reduce their risk of injury?

Barefoot Benefits?

Proponents of barefoot running claim a better landing position on the fore foot and mid-foot during the foot strike phase. This foot strike creates lower collision forces and was certainly re enforced by Lieberman et al (2010) when he published a study in Nature showing lower collision forces when habitually barefoot runners made ground contact compared to habitually shod runners. Some barefoot runners in this study did land in a RFS (rear foot strike), but most did not. The key here is habitual – do we assume barefoot to make those similar adjustments in motor patterning to habitually shod runners? Does it take time to create new motor patterns? With regards to lower collision forces, they have not been shown to decrease injury in runners, so the jury is still out on this one.

Fig 1. Zola Bud (second from right) looks to strike rear foot even as she runs at her pace of close to 3 min/km pace! Not all runners strike forefoot while barefoot running.

There are also claims of a more natural foot strike. Natural does not mean better, we could point out many things that are natural but not necessarily better.

Further research by Lieberman (2012) in a retrospective study on foot strike and injury in collegiate level cross country runners found that those who habitually rear foot strike had twice the rate of over use injuries than those that fore foot strike. While this study is certainly interesting it’s not conclusive. It would be interesting to note whether any of the fore foot strikers who experience injury had biomechanical changes towards a more rear foot strike after injury? It would also be interesting to look at speed of movement – do the fastest runners fore foot strike?

Fig 2. This runner looks to a more midfoot strike during his barefoot gait pattern.

A third study again from Lieberman published this year, (2012) were more economical when wearing minimal shoes (fore foot striking) and again more economical when rear foot striking in minimal shoes when compared to the shod condition. There was no difference in the shod condition between forefoot or rear foot striking. This study agrees that minimally shod runners are moderately more economical than traditionally shod (shoes) runners regardless of foot strike, presumably due to elastic energy storage during the stretch shortening cycle (SSC) in minimal shoe running. This is an interesting study with conflicting evidence.

Fore foot strikers were found to have a more plantar flexed ankle, which is said to attenuate the collision forces by presumably loading through the myo-tendinous structures. These structures are more compliant and return energy via the SSC. They also increase muscle activity and presumably energy cost as their muscles must be used in place of the shoe cushioning. This was investigated in a recent research article when researchers looked at the metabolic cost of running barefoot versus shod. Franz et al. (2012) found the energy cost of running to be no less in shoes compared to barefoot. Previous studies have looked at an energy cost of approx. 1% increase per 100g of shoe on a VO2 max test. This would equate to a 3-4% increase in energy cost for most shoes. This is quite energy expensive over a 10km run.

Franz and his team did not find this, in fact they found for foot wear conditions of equal mass shod running had 3-4% lower VO2 and metabolic power demand than barefoot. Does this mean that shoes may increase performance? More research needs to be done to be conclusive.

If we consider the motor pattern aspect and we have someone who runs in a poor pelvic position (remember this influences foot positioning) by placing (them) barefoot will this simply change their hard wired motor pattern? I am not sure this has been studied but I debate that this would occur.  You would find they would either land RFS or mid to fore foot and destroy their Achilles a few months down the track. This is considering someone who is myofascially stiff and cannot run with his or her pelvis in a neutral to anterior pelvic tilt. More mobile athletes will attain this position more easily. Plantar flexing certainly does attenuate forces, however if you have had previous lower limb and/or calf problems this would be a major risk.

Plantar flexion of the ankle will certainly de-load the knee. A small study at the University of Southern Carolina, Hashish (2011) showed that subjects running shod and barefoot had larger mechanical demands shifting away from the knee in the barefoot condition. The load was transferred to the ankle with a larger percentage taken here. Since knee injuries compose such a large number of total overuse injuries this may be a tick for the barefoot condition. However, if you have decreased range of motion at the ankle or previous Achilles problems this may not be such a good idea.


Further biomechanical changes you would expect to see with changes in foot strike (for most, not all) would be an increase in cadence and shorter stride. This also means less time on the ground – as we know this is the slowest portion of the gait cycle. Deceleration is taken through the SSC therefore braking forces are less when compared to shoes. As discussed above this would partly explain why the ankle is more involved in load transference.

The biggest injury risk is for the lower limb namely the Achilles tendon and boney architecture of the foot. The metatarsals will assume a big load as will the plantar fascia. The soleus and gastrocnemius will work harder as the tendon transfers load though the foot to the lower limb. Wakeling et al (2001) showed myo electrical activity to change depending on the level of cushioning. They found less cushioning increased the activity of the muscles. We would consider that barefoot then produces much higher activity producing the reduced collision forces that Lieberman (2010) talked about.

Anecdotally there are many runners who do well and perhaps perform well barefoot. In my experience, having been a runner for a long time and having competed for nearly as many years, there are stories of triumphs and failures from both sides - the barefoot runners seem to speak the loudest.

Practicalities of Barefoot Running

Barefoot running also has its down sides practically. If you live in a cool climate like I do, there are at least 4 months (sometimes more) where you simply cannot run barefoot – it’s too cold!! Even in minimalist shoes it’s tough. If you have any type of circulatory problems to the extremities in the cold (that’s me) running barefoot ceases to be enjoyable.

Further, brittle skin (cracks in the skin) is acutely painful as are the risks of glass and puncture wounds etc. On another very practical level, I dislike paying more for a shoe (minimalist shoes) where it is quite obviously cheaper to produce with less material than your standard running shoe! That has to be marketing! If you do go totally barefoot, that problem would of course be solved.

So why don’t the most elite runners run barefoot? This would most likely be due to marketing than anything else. You get paid big these days for winning a big city marathon with your sponsors logo! The barefoot technology doesn’t seem to have affected the top echelon (yet) - time will tell. Most of the major shoe companies now make a barefoot minimalist shoe - maybe 2013 will see an increase in this?

What I would like to see is a comparison of the middle distance events with regards to barefoot and performance shoes (spikes) ie; performance over the middle distance on the track. Does barefoot offer an advantage or do we need the grip of the spikes?

The Shoe Story

Shoes – There seems to be little evidence in favour of shoes (Richards et al. 2009). Modern shoes appear to encourage a rear foot strike position (RFS), (Lieberman, 2010) and there is little evidence to support that foot type and shoe type lower injury incidence (Joseph et al. 2010). In fact there seems to be very little evidence for injuries possibly related to pronation and shoe type or shoes overall.

Modern day shoes have advanced significantly since the 1970’s yet injury rates remain high. There could be a number of factors here not just shoes (diagnostic techniques, knowledge of injuries, reporting of injuries, increase in popularity of running etc), we’ll keep our focus on shoes for now.

Ground reaction forces in shoes seem to have a double peak. Clarke et al. (1983) showed that a softer, more cushioned shoe had a similar magnitude force but slower time to reach vertical impact force peak, in other words it takes longer to reach the peak force but the magnitude was the same. Does this matter in terms of musculoskeletal adaptation? Do we need an adjustment [time] going from eccentric to concentric contraction? These are all questions that need to be answered.

In 2008 Wegner et al. showed two types of neutral running shoe to be more effective at cushioning, reducing plantar pressures than a control shoe (Dunlop Volley’s). Further to this Wakeling, Tscharner and Nigg, (2001) found that different materials affected loading rates and muscle activity in the leg as a tuned response to ground reaction forces. They found, depending on the type of cushioning will determine the myo-electrical activity in the leg. Leg activity will be greater in a less cushioned shoe.

The question is “does the reduction in plantar pressure or peak impact reduce injury rates? Does comfort play a role?”. In this same study Wegner (2008) reported the softer neutral running shoes to be more comfortable than a control. If you are running a marathon, you want to be comfortable. This is a practical yet often overlooked component - it is difficult from a comfort point of view to run across gravel laden bush trails – even in minimalist shoes.

So why do so many wear shoes? That’s a really interesting question and for most they probably don’t know or it’s just something that they’ve always done. How much does comfort play a role? It would seem logical that a base of cushioned foam underneath your foot will help protect you from potential injurious loading forces.

If placing cushioning underneath your foot creates a RFS, which increase collision forces – we could ask the question “can we actually run with a forefoot strike in shoes?”. I believe we can – however it would probably take a conscious effort to do so and a lot of effort to change that motor pattern.

Despite a lack of conclusive evidence in favour of shoes, this does not mean they are bad or do not play a significant role in performance, comfort and injury reduction. Just because we ran for 1000’s of years without shoes, this also does not mean that they do not serve a purpose for runners.

The interesting point about injury rates is this; If you had a non runner go out for a 20 min run in running shoes they would probably make it, albeit sore the next day. If you asked that same person to do this barefoot – you would be confident in thinking they would not make it or injure themselves. There are a variety of factors involved here not just myo-tendinous load.

There is inconclusive evidence for barefoot and shoes, though there is a lot of barefoot research being published and looking at shod versus unshod. I think barefoot has some merit, though it must be done slowly initially. Perhaps the very fact you do less running unshod (initially) is one of the reasons you may find a reduction in injury.

Conclusion – The debate with barefoot and shoes will go on. Some will find it the most efficient way to run, others will find it an injury waiting to happen. Only a slow progression and trial and (hopefully not much) error will answer this. If this raises more questions than it answers, then we are in a good place.
Jimmy

References

1. Daniel E. Lieberman, Madhusudhan Venkadesan, William A. Werbel, Adam I. Daoud, Susan D’Andrea, Irene S. Davis, Robert Ojiambo, Mang’Eni & Yannis Pitsiladis, (2010), Foot strike patterns and collision forces in habitually barefoot versus shod runners, Nature 463, 531-535 (28 January 2010)

2. Adam I. Daoud, Gary J. Geissler, Frank Wang, Jason Saretsky, Yahya A. Daoud, and Daniel E. Lieberman, (2012), Department of Human Evolutionary Biology, Harvard University, Cambridge, MA; Department of Athletics, Harvard University, Boston, MA; University Health Services, Harvard University, Cambridge, MA; and Baylor Health Care System, Institute of Health Care Research and Improvement, Dallas, TX , Foot Strike and Injury Rates in Endurance Runners: A Retrospective Study, Medicine in Science and Sports Exercise, Jul; 44 (7):1325-34

3. Franz JR, Wierzbinski CM, Kram R, (2012), Metabolic cost of running barefoot versus shod: is lighter better? Medicine and Science in Sports and Exercise [44(8):1519-1525]

4. Rami Hashish, Sachithra Samarawickrame and George Salem, (2011), Ground Reaction Forces In Barefoot Running Before And After Exertion, University of Southern California, Los Angeles, CA, USA

5. James M. Wakeling, Vinzenz Von Tscharner, Benno M. Nigg, and Pro Stergiou, (2001), Muscle activity in the leg is tuned in response to ground reaction forces, Journal of Applied Physiology September 1,  vol. 91 no. 3 1307-1317

6. C E Richards, P J Magin, R Callister, (2009), Is your prescription of distance running shoes evidence-based?

7. Joseph J. Knapik,, Daniel W. Trone, David I. Swedler, Adriana Villasenor, Steve H. Bullock, Emily Schmied, Timothy Bockelman, Peggy Han, and Bruce H. Jones, (2010), Injury Reduction Effectiveness of Assigning Running Shoes Based on Plantar Shape in Marine Corps Basic Training, J Sports Med;43:159-162

8. Clarke TE, Frederick EC, Cooper LB, (1983), Effects of shoe cushioning upon ground reaction forces in running, International Journal of Sports Medicine [4(4):247-251]

9. Caleb Wegener, Joshua Burns and Stefania Penkala, (2008), Effect of Neutral-Cushioned Running Shoes on Plantar Pressure Loading and Comfort in Athletes With Cavus Feet: A Crossover Randomized Controlled Trial, Am J Sports Med November vol. 36 no. 11 2139-214

10. Lieberman D , Daoud A,  (2012), Effects of footwear and strike type on running economy, Medicine in Science and Sports Exercise, Jul;44 (7):1335-43



















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