As the bare-foot vs. shod running debate continues to rumble along, one of the arguments that I have come across was the idea that running barefoot is more efficient because as we add weight to the foot, the effort required to run increases and therefore efficiency decreases. The conclusion is often made, therefore, that if you are wearing nothing at all on your feet then you must be as efficient as it is possible to be.
But now a study by Jason Franz, Corbyn Wierzbinski and Rodger Kram published in Medicine & Science in Sports & Exercise, seems to refute this assertion entirely. The report, entitled ‘Metabolic Cost of Running Barefoot versus Shod: Is Lighter Better?’ suggests that in fact running with lightweight shoes is more efficient than running barefoot and that whilst adding weight to both a shod and an unshod runner’s feet does indeed make them less efficient – as measured by oxygen consumption at a fixed pace – to the tune of an extra 1% more oxygen required for every 100g added to each foot, the efficiency both types of runners deteriorates at the same pace from a starting point where shod runners are more efficient.
The report goes on to suggest that one positive effect of running shoes is that:
the runners spontaneously took slightly longer strides (by 3.3% on average) when they were wearing shoes. These longer strides may have allowed them to be more efficient, thought it’s unlikely to account for the whole effect. (Runners World US)
The other positive impact of shoes that the report suggests might be a factor is the cushioning: without cushioning, the researchers argue, the runners’ leg muscles have to expend energy absorbing the impact of the stride, which in itself requires increased oxygen consumption.
There are a few points to remember about this report. The runners chosen for the report were experienced barefoot or minimalist runners (they were running at least 5 miles/week barefoot) in order to avoid the data being skewed by the runners needing to learn to run barefoot.
Another important point is the type of shoe that the runners wore – Nike Mayfly. These are super-light (Runners World US suggests 139g for a UK size eight) and probably not the sort of thing that people wear regularly. But the researchers showed that even when 450g had been added to the runners’ feet, the shod runners were not less efficient than the barefoot runners, so it might be inferred that even the weight of shoe is irrelevant.
So where does this leave us? Well, I like the idea that barefoot and shod running are two sides of the same coin. I believe that running barefoot or in minimalist shoes (and certainly wearing nothing or very light shoes when walking around) is a great way to strengthen feet, but I am also pretty sure that I couldn’t run as fast with nothing on my feet as I can in a pair of lightweight racing flats. What are your thoughts?