Also, new studies on foot muscles and anaesthetising the soles of your feet.
Sports scientists from around the world recently gathered in Denver, USA, for the annual meeting of the American College of Sports Medicine. It’s the biggest sports science conference in the world, and the new results presented there will provide plenty of fodder for discussion in the weeks to come.
For starters, here are three results that were presented during a running-focused poster session.
Better form makes you less efficient?
Jacob Lee and his colleagues at Utah Valley University presented the results of a running form intervention in which seven subjects were coached on “proper running mechanics” for a week, with a particular focus on “improving arm movement and cadence” to improve running efficiency.
Sure enough, 3D stride analysis showed that the runners were able to reduce their upper body movement, and they reported “working less intensely to run at the same rate”.
The problem? Actual measurements of energy consumption showed they were running less efficiently, and burning more energy.
This is by no means a surprising result, as it’s pretty well-established that changing your ‘natural’ running form will cause you to get less efficient, at least in the short term, as you adjust to new muscle patterns. Whether you ultimately become more efficient once you adjust to the new stride remains somewhat controversial. Many researchers assume this to be the case for well-designed interventions, but there’s not a lot of data out there demonstrating that it’s true, or showing which interventions ultimately improve efficiency and which don’t.
What caught my attention here is the disconnect between the perceptions of the runners, who felt like they were getting more efficient, and the cold hard measurements. That’s why, without meaning to sound too harsh about it, I basically disregard when people tell me they’ve tried New Fad X and it makes them feel wonderful: I have very little faith in the ability of anyone – myself included – to self-judge subtle changes in efficiency. Measure it (and get it peer-reviewed), or it didn’t happen.
A longstanding bone of contention in the barefoot debate has been whether shoes make your feet “weak.”
There’s a certain logic to the idea. If shoes help support your feet, they presumably take on some of the roles that would otherwise be played by muscles in your feet. As a result, those muscles presumably aren’t taxed as much, and get weaker. The resulting weak “foot core” might leave you more vulnerable to injury, even in shoes.
But logic takes you only so far. Does this actually happen in real life?
A team at Brigham Young University in the US led by Sarah Ridge presented a comparison of the size and strength of the foot’s “instrinsic” muscles (the 11 muscles located entirely within each foot) in 21 female runners and 13 female gymnasts, because gymnasts train and compete in bare feet.
Of the four muscles measured with ultrasound, the gymnasts were significantly bigger on average in two of them, with no difference in the other two. The gymnasts were stronger in their ability to flex their big toe, with no difference in the strength of the second, third, and fourth toes.
I think this is an interesting finding, though (as the authors point out) it’s not clear the gymnasts are a fair comparison. They have to perform very specific tasks – balancing on beams, for example – that require exceptional foot strength and stability. It may be that gymnasts have stronger feet than average, rather than that shoe-wearing runners have weaker feet.
And of course, even if it does turn out that shoe-wearing runners have weaker feet, the more important question will be: does it matter?
The feel of the ground
One of the theories about the benefits of barefoot running is that it allows you to feel the ground – this feedback, through the sole of your feet, helps guide you to adopt a sustainable running stride.
There have been reports over the years that support this view, for example suggesting that “a thin pair of socks causes a statistically significant reduction in balance, suggesting that they filtered out important sensory information”. But the idea remains mostly speculative.
A presentation from Melissa Thompson of Fort Lewis College and Kristine Hoffman of Denver Health Medical Center tested this theory by having runners complete a series of short runs over a force plate, with and without shoes, and with and without an injection of lidocaine to anesthetize the soles of their feet.
The differences between running with and without shoes were pretty much as expected. Without shoes, the runners shortened their stride, were more likely to land on their midfoot or forefoot, and experienced smaller impact forces.
But these differences were entirely unaffected by the presence or absence of anaesthetic, suggesting that whatever ‘feel’ we get from the running in direct contact with the ground isn’t from the superficial sensors on the skin. This also suggests that running in socks, or perhaps very minimal shoes, would produce basically the same effects as running in bare feet.
Is injecting lidocaine into your soles really a fair test of this question? I’m not sure, never having run with anesthetized soles before. Maybe it changes too much—but the fact that running stride and impact forces stayed pretty similar suggests that people can run pretty well without those sensations.