Back on June 17 I introduced the concept of shear with a post by podiatrist Rebecca Rushton from Australia who has studied blisters and identified shear as a major factor in blisters.
It’s best to start by refreshing our memories about what was shared on the previous article. Here’s the link in case you want to see the full post: An Introduction to Shear and Blister Formation. Otherwise, here’s a short piece from that post:
Poor blister prevention outcomes are due in no small part to the misunderstanding of the cause of this obstinate injury. The force that causes ‘friction’ blisters is not friction. And it’s not rubbing. It’s shear. But if you ask 100 people the question “what causes blisters”, nobody would answer “shear”. Shear is the sliding of layers across one another – internal layers that are structurally connected. Those connections can break and when fluid fills that cavity, you have a blister! What Does Shear Look Like? Try this … 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. 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. Your skin doesn’t need anything to rub over it for blisters to form. It just needs shear (this stretching of the internal tissue layers) to be excessive and repetitive.
Managing shear is key to managing blisters. Let’s look at several ways to reduce shear.
The first way is to make sure your footwear fits. Many people buy shoes that seem comfortable in the store but don’t make sure they feel ok by wearing them around the house for a few days. Make sure they have enough room in the toe box both in height and length. Make sure there is not undue pressure on soft tissues over any bony spots (sides of the forefoot, ball of the foot, sides and back of the heel, over the instep, etc.). Make sure they are not too loose, allowing too much movement leading to skin abrasions, hot spots, and then blisters.
Using a cushioning product is a second way to reduce shear. This might be a gel pad under the ball of the foot or under the heel bone, or a replacement insole meant to pad and cushion.
A third method is to manage skin moisture. This can include skin-drying strategies and skin lubrication. Studies have shown that you can reduce the incidence of blisters by keeping the skin either very dry or very wet. Drying the skin can be done with powder, benzoin, alcohol wipes, and antiperspirants. Lubricants can include SportSlick, BodyGlide, BlisterShield, and other popular products. Zinc oxide is also effective at controlling moisture. The method of having runners train with wet feet has been successfully used by Shirley Thompson and Vicky Kypta of the Jungle Marathon Amazon. They have found that the feet of their race participants have been better with this suggestion given to runners before the race.
The fourth method of controlling shear is with socks. This may include double layer socks or wearing two pairs of socks – a thin liner and usually, a thicker second sock. This allows movement between the two sock layers. Injinji toe socks are great for those with toe blister problems.
Next time, we’ll talk about a fifth way to reduce shear – Engo Blister Prevention Patches.
In the mean time, check out ZombieRunner for many products that can help with cushioning, skin-drying and lubricants, and socks.
Filed under: Foot Care, Foot Care Products, Footwear, Footwear Products, Health
Generally foot odor and athlete’s foot do not come from sweat, which surrounds your feet. It comes from bacteria on the skin, which is decomposed by the sweat. The waste product of this decomposition leaves a very unpleasant smell and is an ideal breeding climate for athlete’s foot and nail fungus.
The Zederna Insole is a 100% natural product from thin cedarwood. The back consists of a stabilizing cotton layer. The sole is flexible and adapts to your foot form after a few steps. It gives you a very comfortable feeling (even if you carry orthopedic inserts). Your feet can take a deep breath nearly as liberating as walking barefoot.
Here’s how Zederna Insoles work:
- The natural suction force of Zederna cedarwood absorbs the sweat effectively
- The Zederna Insole and its antibacterial effect work where foot odor and athlete’s foot develop
- Smell and fungus creating bacteria are eliminated
Here’s my take on the insoles. I wore a pair in my work shoes for months. My old insoles were a regular stock style and I used them because they were already in the shoes. I immediately liked the Zederna Insoles. I felt my feet were cooler and more comfortable. I liked the wood feel – my feet were not stuck to a fabric synthetic insole, but could move around on the cedarwood. Between my commute and work, I had my shoes on for 12 hours straight. The insoles were pleasant. They are perfect to use in your shoes after training.
Because they are thin, I think they could easily be used in running shoes or boots. I would wear them in training, and then, depending on the feel, I’d make the decision to wear then in a race or not.
Zederna Insole Advantages:
- Foot odor disappears immediately!
- Athlete’s foot disappears after a few days.
- The new formation of athlete’s foot is permanently prevented.
- The treatment of existing nail fungus with conventional methods is accelerated by more than 50%, because of the dry and antibacterial foot climate.
- The new formation of toenail fungus is permanently prevented.
- Plug & play: Just insert the insole in your shoes and start. Annoying treatments with gels and powder belongs to the past.
- Naturopathic treatment: The effect is purely based on natural power. No chemistry.
- As a result of the polished surface and the flexibility of the Zederna Insole, pleasant feeling arises also when wearing without socks.
- The Zederna inserts provide a pleasant and dry climate in your shoes. Comparable to walking in a forest: in summer it is relatively cool and in winter it is always warmer.
- Long durability of the Zederna Insoles.
- Reliable quality – Made in Germany.
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Disclaimer: I received a pair of Zederna Insoles to try. Beyond that, I have no financial investment in Zederna.
Several years ago I met Gregg at Badwater in Death Valley. We were in line to check in at Furnace Creek and I heard the last name. It was the same as an aunt of mine. Turns out we are related.
At Badwater he ran well and finished near the top. Later that year, he and his wife moved to Asia and I had not heard from him – until the other day. He sent an email about running the Spartathlon in Greece. It’s a 246-kilometer (153 mile) race between Athens and Sparta. The Spartathlon aims to trace the footsteps of Pheidippides, an Athenian messenger sent to Sparta in 490 BC to seek help against the Persians in the Battle of Marathon. Here’s his email:
I just finished running Spartathlon. It was nearly as hot as Badwater (100.4), ok maybe not as hot as Badwater, but it was far to hot for this race, considering it is normally 86. The race by the way is fantastic; I would highly recommend that you make a trip out there if you get the chance.
So, I took a photo of my feet after the race and thought you might like the photo, being that you are the foot guy. Might make for a good example. The blister appeared to start from underneath the pad of my foot by my big toe. The pressure built up so much that it formed the blister on top of my foot as well – as you can see from the photo. Pretty cool if you ask me. I probably ran with it for 50 miles, since I didn’t change my shoes and didn’t feel like taking them off. They lanced it when I finished… as I was receiving two bags of IV fluid. Haven’t had any problems with it since, although it has taken a few days for the pressure under my foot to slowly recede.
As you can see in the photo, there is blood in the blister. Here’s where you have to be careful and take precautions to prevent infection. I don’t encourage people to lance these on their own, but in aid stations with the right equipment and knowledge, it can be done. When I do it, I always give the athlete the warning signs of infection: redness, warm to the touch, pain, fever, pus, and swelling. If you have a blood blister, be careful.
Really though, Gregg’s feet look pretty good for just having run 153 miles. Don’t you agree?