Pronation is the the foot and ankle’s natural inward roll when a runner’s foot contacts the ground, and not only is it natural, it’s essential for efficient running. Most runners naturally strike the ground with the foot’s outside edge. Then, ideally, the foot rolls inward, to allow the middle and inner edge of the foot to contact the ground. As the foot approaches toe-off, it starts rolling back towards the outside. This is called supination.

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Too little pronation and too much pronation (what runners and marketers selling stability or motion-control shoes refer to as over-pronation) can both lead to increased risk of injury. But how much is too much, and how little is too little?

How do we measure it?

There are different ways to measure pronation, for example using high frame-rate motion-capture imaging from a perspective immediately behind the runner. But to measure pronation consistently both indoors and outdoors, the best solution is with a small footpod (inertial measuring unit) that can reliably measure pronation values simultaneously on the left and right sides.

What is normal pronation?

The amount you pronate changes as your pace changes–the faster you run, the more you pronate. Values may range from 2 degrees at one (minimal) extreme to 30 degrees at the other extreme, but healthy pronation ranges from about 5 degrees to 20 degrees, depending on other variables such as the runner’s injury history.
Malc Kent of Runfisix in Calgary says, “I regularly see runners with numbers outside of this range, who either have too much or too little ankle motion, and related injury issues… When I measure someone outside in a workout and they record, say, 15 degrees, then I tend not to worry about it.” This highlights another key point–outdoor measurement. Pronation is something that will likely change in absolute numbers depending on the surface underfoot, so it’s quite important to measure it outside (using foot pods) when possible.
Also, symmetry is important: investigating the difference between the left- and right-side numbers can provide as much value as the overall numbers themselves.
Very high or very low numbers or large left-to-right asymmetries are red flags, and Kent says that as a general rule of thumb, he’d be concerned to look more closely at anything above a 20 per cent difference between right and left.
Pronation velocity, or how fast the pronation occurs, is also important to measure, since it tells us how much the runner’s muscles can control their pronation. Very high pronation velocity indicates high instability and low muscular control.

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