There's something you don't understand about friction. And that friction blister on your foot needs you to know this! Rest assured, this is not your fault. We'll blame the English language! While many words in the English language have different meanings, by and large, we get by without too much trouble. But in the case of friction, its two definitions are not only different, they're opposite! And we have not managed to negotiate this when it comes to foot blisters.
This conflict has clouded our understanding what really causes blisters on the feet, how to truly prevent them, and how to providing meaningful relief when treating them.
BTW, conflict is actually the third definition of friction - see what I did there :)
The 2 definitions of friction
Friction Definition 1: The action of one surface rubbing against another.
Friction Definition 2: The resistance that one surface encounters when moving over another.
In other words, it means both rubbing and the resistance to rubbing.
By using definition 1, high friction means lots of rubbing. But using definition 2, high friction means not much rubbing - because there is lots of resistance to the movement.
By using definition 1, low friction means not much rubbing. But using definition 2, low friction means more rubbing - because there's less resistance to the movement.
A friction blister example for you to consider
Think back to your last friction blister on your foot - that one on the back of your heel, under the ball of your foot or on your toe. You treated it with a plaster or bandaid or tape, right? You know, to stop that friction (using definition 1).
The problem with using the "rubbing" definition of friction is we know rubbing doesn't cause blisters. Blisters on the feet are caused by shear distortions and these occur due to the "grippiness" (resistance to movement) second definition of friction. Please, I implore you to read this article to become crystal clear on how foot blisters form.
Remember, when referring to blisters, friction is about grip; the resistance to rubbing, not rubbing.
- High friction means two surfaces grip together.
- Low friction means they don’t … they’re slippery.
Let's talk about friction levels
There are relatively high friction levels in your shoe. That's because of the materials lining your shoe, plus your socks, plus the fact that the feet sweat a lot and there are limited opportunities for evaporation. All of this means your skin grips your sock; and your sock grips your shoe. They all grip together so your foot doesn’t slide around in there.
But your bones aren't stuck. They move around within your foot with every step you take. Now, considering the skin and bone are tethered, as the bones move and your skin doesn't, everything between skin and bone stretches and distorts. These are the shear distortions that cause blisters.
Shear distortions need high friction levels to get anywhere near blister-causing. Here's how it works (image below). If you can reduce friction levels, you can prevent friction blisters on your feet.
In-shoe friction conditions for blister formation / blister prevention
The importance of friction to blister treatment, too
You can stop a friction blister on foot in the first place by cutting friction levels – this is smart! But if you miss the blister prevention boat, you'll want to know how to heal that blister fast, and make it hurt less.
The answer is not a blister plaster. The answer is to cut friction levels (ie: add something slippery). Make it less grippy (more slippery) where your friction blister is. Because if you don’t, that stretching and distorting continues at the blister base while it’s trying to heal, making it hurt more, and taking longer to heal.
Most people don’t know to do this
Because they’re caught up with thinking friction is rubbing. But by making it less grippy (more slippery), just where the blister is, I can get runners back up and on their feet again, with even the worst friction blisters!
So how can you cut friction levels? Pick one of these:
LubricantsPowdersAntiperspirantsTapes (maybe)Moisture-wicking socksDouble socksENGO Blister Patches
ll of these cut friction levels. Some work better than others. In other words, some don’t get friction down low enough, for long enough. And so when friction inevitably rises, everything grips together again. And you’re back to square one. But one or two work brilliantly, keeping friction very low for very long. My favourites are Engo Patches, 2Toms BlisterShield Powder and Armaskin double-socks.
So if you’ve got a friction blister on foot, make no mistake
So if you’ve got a friction blister on your foot, make no mistake. You still need to put a plaster over it. To protect the fragile blister roof and painful blister base. But to truly be effective at treating it, you will need to cut friction levels. This will ensure your blister can heal quickly and hurt less.
Figure out which of these friction-cutting strategies is right for you - right for your feet, your shoes, your activity and your lifestyle. And have it handy for when you next get a blister. You’ll thank me!