Video: What Causes Foot Blisters From Running?

Foot blisters from running are one of the most common yet unreported injuries in sport. At best, running blisters take the fun out of training and reduce performance. At worst, they can cause serious ill-health if not dealt with appropriately. Let’s take a look at what causes foot blisters, and how we can use that knowledge to make our running blister prevention strategies more effective in having a solution for how to prevent blisters.

Athletes know just how important blister prevention is and consider it an essential part of their preparation. Unfortunately, your success in learning how to prevent blisters continues to be rather hit and miss. The purpose of this article is to help you understand what causes blisters and where your opportunities for running blister prevention may lie.

What Causes Foot Blisters from Running?

Most people think friction is what causes foot blisters. But friction is only part of the blister story. Blisters are caused by shear. Shear is the stretching of skin and soft tissues. Too much shear causes micro-tears to occur just under the skin surface. These tears fill with fluid which results in a blister.

The following video does a great job of explaining what causes foot blisters:

Shear is influenced by three things:

  • Skin characteristics
    Making some areas of the body, and some people, more prone to blisters than others.
  • The movement of the bones
    The more the bones move relative to the skin, the bigger the chance of shear injury.
  • Friction
    Friction is not rubbing. Friction is the force that keeps two surfaces in stationary contact with one another. Foot blisters occur when high friction keeps the shoe, sock and skin stuck to one another while the bones move back and forth causing stretching of the skin and soft tissues in between. This is what causes blisters; shear not rubbing!

Once the cause of blisters is understood it allows for a purposeful approach to how to prevent blisters. The flowchart below identifies factors relevant to blister causation and the opportunities for prevention.

What Causes Foot Blisters From Running? Running Blister Prevention

How to Prevent Running Blisters

Pressure is a factor that enables friction to become blister-causing. Therefore cushioning and other methods of pressure reduction, like Sorbothane insoles, Moleskin and silicone gels, can be helpful in preventing running blisters.

But many runners will acknowledge that cushioning alone is not the holy grail of blister prevention. Also the more cushioning you add to your shoe, the tighter it becomes and pressure increases elsewhere. So try cushioning and pressure deflection by all means but be aware it may not be enough.

How to Prevent Blisters: Tapng

Sports tape does not necessarily reduce shear. Very slippery tape like Gaffa Tape might, but traditional brown sports tape is much less likely to provide a solution in how to prevent blisters. Yet sports tape remains a very popular running blister prevention method used by runners. Why?

The answer to the conundrum ‘how to prevent blisters’ is to reduce nasty effects of rubbing: abrasions and chafing. The previous video showed that you do not need rubbing to cause shear (and therefore blisters). But the two often occur at the same time.

When rubbing occurs over a blister, it de-roofs it and you’re left with a red raw sore. Tape provides protection to the skin so that the blister roof is more resistant to rubbing. The blister will still form, but at least the top won’t get rubbed off. There is no doubt that’s a good thing; a de-roofed blister is not only painful but at risk of infection. But sports tape often doesn’t prevent the blister, a fact that many athletes know from bitter experience.

Indiscriminate vs Target Friction Reduction

Friction is necessary to walk and run. Without it, the lack of traction would make the foot slide around too much in the shoe making it difficult to keep your balance. And it would make propulsion all but ineffective. Yet many runners, in their efforts to reduce friction, take it too far with lubricants. Lubricants like Vaseline applied all over the foot has this very effect. Black toenails and bruising are common consequences. Yet, as the lubricant absorbs and disperses over time (after one hour) friction has been found to increase above baseline measures.

There are many runners using lubricants successfully in preventing blisters. If you’re new to this strategy, I would suggest a more targeted approach by applying to problem areas only and for exercise duration of under one hour.

The Shoe-Sock Interface

The most widely used preventative measures focus on the area between the skin and the sock (skin-sock interface). The difficulties here centre mainly on the effect of perspiration; it loosens adhesive products and dilutes preparations applied. Skin irritation is also an issue for some.

The shoe-sock interface is an area that may hold more potential for longer-term blister prevention. ENGO Patches are used in this way. They are self-adhesive patches that stick to the inner shoe surface including insoles, orthotics and inside shoes, not the skin. The friction level when using ENGO is reduced by up to 80%. ENGO patches are used to target high friction at problem areas only whilst maintaining normal friction necessary for efficient gait. They are thin enough to not affect shoe fit (0.38mm); durable enough to last 500km and the low-friction properties are maintained even in moist conditions.

How to Prevent Blisters: Take Home Messages

Blister prevention tends to be a hit and miss affair partly because blister causation is poorly understood.  But the flowchart identifies there are many opportunities for how to prevent blisters, depending on factors relevant to the individual athlete. Some of the running blister prevention strategies are better than others. Personally, I think altering your activity in an effort to avoid blisters is unacceptable, but others are happy to take that route. I’m a big fan of ENGO Patches but as you can see, it is only a tiny piece of the whole blister prevention story. There are pros and cons to each strategy and what works for one might not work for another.
The challenge for runners who experience foot blisters is threefold:

  1. To look past preconceived ideas of the causes of blisters to fully understand what causes foot blisters
  2. Take a more structured approach to figuring out how to prevent blisters rather than the hit and miss approach of yesterday
  3. In order To find a running blister prevention strategy (or combination of strategies) that work for you

About The Author

Rebecca is a Podiatrist working full time in her own private practice in Esperance Western Australia. She completed her Bachelor of Science in Podiatry at Curtin University in 1993. She has a personal and professional special interest in blister prevention and is a member of Sports Medicine Australia and the Australian Academy of Podiatric Sport Medicine. Visit Rebecca's Website

 

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7 Comments

  • Rebecca, thank you for this considered and excellent approach to blister management. Monica put me on to you last week and has forwarded the kinetic brochure as well. I have shared this with Tamsin already and I am really enthusiastic about offering our Busselton blister patients a great alternative to the existing methods.
    I just need to purchase some Engo now.

    Regards, Jennifer Russell

  • Thanks Jennifer, I’ll be only too happy to help.

  • […]  at Kinetic Revolution […]

  • […] website, which has loads of excellent articles, including this one written by Rebecca Rushton http://www.kinetic-revolution.com/5-insights-for-running-blister-prevention-success/ which is the first article I have read that actually acknowledges bone movement and biomechanics as […]

  • Thanks for the article.

    Could you please clarrify the difference between rubbing and shearing. I would have thought rubbing was a form of friction which in itself falls within the parameters of shearing force???

    Thanks again

  • Sure Christian,

    Rubbing is what’s happening on the surface of the skin. Shearing is what’s happening internally. Shear is the parallel sliding of tissue layers over one another. This might help explain:

    STEP 1 Place the tip of your right index finger on the back of your left hand.

    STEP 2 Wobble it back and forth but keep it stuck to the same bit of skin. Notice how your skin stretches? This is shear and this is what causes blisters. Keep wobbling as you read:

    Shear might look like rubbing but it’s not. Notice how your finger tip has not moved relative to the skin of the back of your hand? But your hand skin has moved relative to the underlying bone. This is shear. When shear is excessive and repetitive blisters form – it’s that last little bit of shear that is damaging, when there is maximum parallel stretch within the skin.

    In practical terms, shear does occur when there is rubbing, but interestingly, rubbing lowers the shear peak (read more about peak shear here: http://www.blisterprevention.com.au/blister-blog/friction-blisters-what-is-friction ).

  • […] website, which has loads of excellent articles, including this one written by Rebecca Rushton http://www.kinetic-revolution.com/5-insights-for-running-blister-prevention-success/ which is the first article I found that actually acknowledges bone movement and biomechanics as a […]

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