Still Learning Foot Care

April 20, 2018 by · Leave a Comment
Filed under: Foot Care, Footcare, General, Sports 

I have been doing foot care for more then 20 years–and some things don’t change. What disturbs me is that there are still large numbers of athletes who seem to give little thought to their feet. Oftentimes these are newer runners, newer adventure racers, and new hikers. They come into the sport without a base of knowledge and awareness of the best ways to manage their feet. They make mistakes. Many times they don’t have buddies who help them learn about foot care. Maybe you can be someone who helps another learn. I encourage you to  try it.

So here are my thoughts on things they need to understand. The athletes with the most foot problems share the following characteristics:

  • They shove feet into shoes without straightening their socks.
  • They wear the wrong socks and do not look inside their socks for seams that cause toe blisters.
  • They have sacrificed fit and buy a shoe because a friend recommended it and not because it was the best shoe for their feet.
  • They try to fix blisters with Band-Aids.
  • They fail to change their socks often enough when their feet are wet.
  • They fail to trim their toenails and wonder why they get black toenails and toe blisters.
  • They fail to put in the miles that their feet need to be toughened for the rigors of racing.
  • They speed through checkpoints feeding their faces but not tending to their feet.

As Billy Trolan, MD, said in the foreword for the first edition of Fixing Your Feet, “The one factor that continues to amaze me is that individuals and teams will spend vast amounts of money, time, and thought on training, equipment, and travel, but little or no preparation on their feet. Too often the result has been that within a few hours to a few days, all that work has been ruined. Ruined because the primary mode of transportation has broken down with blisters.” That was written in 1997 and is still true today.

Results of Tape Survey

February 19, 2018 by · Leave a Comment
Filed under: blister care, Foot Care, Foot Care Products, Sports 

I recently asked two questions in an online survey. Very simple questions.

  1. What is your favorite tape for pre-taping for blister prevention?
  2. What is your favorite tape for blister patching?

KT Pro TapeThere were 57 responses.

Let’s start with the first question. What is your favorite tape for pre-taping for blister prevention?

The tapes ranked highest were, Leukotape P and KT Tape kinesiology tape both at 19.3%. However if you add all the kinesiology tapes mentioned, it’s a different outcome. With KT Tape at 19.3%, RockTape at 12.3% Strengthtape at 7%, and Kinesio Tex at 3.5%, the total of all kinesiology tapes is 42.1%. With those numbers, more than twice as many are using kinesiology tapes at 42.1% versus Leukotape at 19.3%. Worth noting is the mix of HypaFix, Coverall, and Fixomull came In at 14%. These three are basically the same kind of tape, which is great for toes. Micropore paper tape came is at 7%. Surprisingly, duct tape came in at 7%.

Now let’s look at what some people said under the “other” choice, which came in at 21.1%. What I was looking for was other types of tape. Unfortunately, some of the answers were things like, Trail Toes; none, I stopped taping five years ago; and I don’t get blisters. Also in the other column was one person who said surgical paper tape, which is the same as Micropore; and two that mentioned Elastikon, which is hard to find and has fallen out of favor with most runners.

The second question was what is your favorite tape for blister patching?

Here the tapes ranked highest were Leukotape by a large margin at 29.8%. But again, add up all the kinesiology tapes with KT Tape at 19.3%, RockTape at 12.3% Strengthtape at 7%, and Kinesio Tex at 3.5%, the total of all kinesiology tapes is 42.1%. So again, kinesiology tape scored highest, but by a narrower margin.

In the “other” choice, 21.1% were a variety of answers. Two again mentioned Elastikon, Trail Toes was again mentioned, and several said they don’t blister or don’t know how to tape, along with a few other mixes of answers. Some of the other comments were that runners used a mix of two tapes, or moleskin and one of the tapes.

So, was did I learn from this?

Kinesiology tape is popular but Leukotape P is a strong second. Leukotape is known for its aggressive stickiness, which is great for adverse conditions. It’s inexpensive and easy to apply, although it does not conform to the shape of one’s feet. It also leaves tape residue on the skin when worn for long periods like 24 hour and multi-day races, which makes good foot care hard to do. I will always keep a roll of Leukotape around for times I think it’d be the best tape.

Kinesiology tape is easy on the skin, and when applied correctly, will stick for long periods. When used with a tape adherent, it will stick for days. It conforms to any shape of your feet and it breathes well. The trick with any of the kinesiology tapes is to prepare the skin with an alcohol wipe, use a tape adherent, apply the tape with little to no stretch, and then rub the tape with the paper backing for 20 seconds to warm the adhesive to help the tape stick. It’s best to tape before it’s needed, like the night before if possible, or a few hours before.

I like it the large percentage of people who use either Micropore paper tape of one of the HypaFix, Coverall, or Fixomull tapes. These tape are easy to use and quick to put on. They are thin and don’t require any special cutting to work. They are great for toes, as I mentioned earlier, but also work well for a quick covering for a hot spot or to hold a blister patch against the skin. Of the two types of tape, I prefer one of the HypaFix, Coverall, or Fixomull tapes because they are wider than most commonly carried paper tapes, which means often one piece will do.

And of course with any taping on your feet, make sure to bunch up and roll your socks on and off. This keep the socks from pulling on the tape. When cutting the tape, round any corners—square corners start to peel off fast when putting socks on and off.

Some of you might ask, what I carry in my foot care kit. It’s easy, several types of kinesiology tapes in two and three or four inch rolls, a roll of Leukotape, and a roll of HypaFix.

If you want to check out kinesiology tapes, here’s my favorite source:


An Advanced Course about Maceration

Several weeks before Western States last year I wrote a blog post about conditions on the course and how feet were going to be wet. The title was Running a Wet 100-Mile Trail Run. I talked about what would happen to runners’ feet, and steps I would take to manage my feet if I were running. Based on the feet we saw on the course, the majority of runners did not read the post and if they did, they ignored the advice.

In a normal year at Michigan Bluff, we treat 40-60 runners for blisters on the heel, forefoot, arch, and toes. Last year we treated one, yes – 1 for blisters. Everyone else had feet in a different stages of maceration. It was clear than runners did not take steps to manage their wet feet.

My friend, Rebecca Rushton, is a podiatrist in Australia. She wrote the forward for the 6th edition of Fixing Your Feet and I value her opinion on fixing feet. She’s very sharp and manages the website Blister Prevention. Yesterday Rebecca send out an important email about the question How Do I Keep My Feet Dry?

I want to share Rebecca’s email and the links to her three articles on maceration. It’s like an advanced course about maceration. I urge you to take a few minutes and read all three articles and heed her advice. The three articles cover the problem (maceration), treatment, and prevention. In my opinion, it’s a must read.

Here’s the email from Rebecca:


Most people know that moisture increases friction levels; and higher friction levels means more blisters.

So keeping the feet dry is an important blister-busting aim.

That’s a tough gig! Think about how your feet are wrapped up in shoes and socks the whole time. How can you keep the skin dry from the sweat being expelled from the skin? And dry from water coming into the shoe from the outside (environmental water – puddles, rain, dew, river-crossings, water tipped over the head which runs down the legs and into the shoes)?

Blisters are one thing. But in extreme waterlogging situations, the skin can become macerated. This is something every single athlete wants to avoid!

I’ve written a series of 3 articles on this very subject. If your feet are going to be exposed to water for an extended period of time, you owe it to yourself to read these articles.

And a word of warning … there are some pretty shocking photos in here. Don’t say I didn’t warn you! Talk soon 😉



Here’s the link to the first article on the problem of maceration. Each article has a link to the next article so you can read all three.

Another Horrific Blister Story

January 28, 2018 by · 2 Comments
Filed under: blister care, Foot Care, Footcare, General, Health, Sports 

Last July I wrote a blog post about The Year’s Best Blister Horror Story. I told how Marin Cilic was unable to continue in his championship tennis match at Wimbledon against Roger Federer—because of a blister that formed under a callus on the ball of his left foot.

Before you decided to skip reading this post because it’s about a tennis player, please know there is an important lesson here for any athlete. Fast forward to a couple of days ago, to the Australian Open where Roger Federer is playing against Chung Hyeon in a semi-final match. Here’s the headline: Australian Open: Hyeon Chung reveals the extent of blister that forced him out of semi-final with Roger Federer. The same thing happened! A blister. Chung had to withdraw from the tournament because of a blister on his left foot. Depending on the news source, he had one blister on the left foot or blisters on both feet. Above is a link to the story.

Federer won over Marin Cilic in the championship on Sunday. They had said that this would be a repeat of last year’s final day at Wimbledon. But no mention was made about how a blister affected the outcome of that match too.

Photo 1 – What’s on his foot?

I have a few photos of Chung’s foot and blister and will give my interpretation of what I see and then what can be learned from the incident.

In this first photo, I can’t tell what the white stuff is on Chung’s foot. It could be some kind of cream, zinc oxide, or even tape residue from that that was removed. It appears to spread across the whole ball of the foot. I would love to know what this is.

Photo 2 – Some kind of tape patch/covering

In the second photo, some kind of tape patch is being applied to the whole ball of the foot down into the arch area. Would love to know what this stuff is.

Photo 3 - Fully patched foot

Photo 3 – Fully patched foot

The third photo shows Chung’s fully tapes and wrapped foot. It could be Coverall, or HypeFix, or what is Australia is called Fixomull, a thin soft cotton type tape. Unfortunately they did not put one or two figure 8 pieces of tape between the toes from bottom to top to anchor the forward edge of the tape and keep it from rolling. I would have loved to have seen the patch job when they removed his socks.

Photo 4 - Deep blister on left foot

Photo 4 – Deep blister on left foot

The fourth photo shows the blister. It’s hard to tell whether this is a fully deroofed blister going down several layers of skin, or a blister that split open and foot strike pressure opened it even more into a gaping wound. I see tape residue on the skin and the tapes mentioned above do not leave such residue, so something else was used. Maybe white athletic tape or Leukotape P. There appears to be a small blister in the arch of the foot too.

Watching a championship tennis match with the world’s best payers, you can see the way their feet move. There is an extreme amount of side-to-side shear, and front-to-back shear, as well as rotational shear. Compounding the shearing movements is that they are made as the foot is landing on the court surface. It’s instantaneous under a lot of pressure. Unlike runners when a foot is planted and moves through its foot strike, tennis players subject their feet to much more shear and it can change each time the foot lands.

So the question is what can we learn from this?

Go back to my post from last year about Marin Cilic’s feet to see what I would have done for him. Not much would have changed here. I would have filled the open blister with a cut and shaped wound care pad. Even though I have years of experience patching feet, I would have patched Chung’s feet based on what I saw, customized for him. I also read that this problem started to develop a day of two before. It’d be nice to know what they did than as a preventive measure.

So what’s the lesson here?

It goes without saying that we are each responsible for our own feet. When you rely on others for their expertise, or lack thereof, and their supplies, or lack thereof, you sometime win and sometimes lose. A lot of questions should be directed at Chung’s coach and trainers. Did they follow best practices in their treatments? Who worked on Chung’s feet, both in the days leading up to this and at the final event? Did they have the knowledge and skills, and the materials to do the best patch job possible?

It’s just like running into an aid station at a 100-miler, and needing foot care, you get what’s there. It could be pot luck. That said, I know all the people I’ve seen work on feet try their best and I am not suggesting Chung received less than stellar care. But I do know from experience that patching a blister on a runner in a ultramarathon or multi-day race takes a certain amount of knowledge and skill. More than most medical people have. I still vividly remember many years ago at WS100, watching two podiatrists wrap a runner’s foot with half a roll of white athletic tape in a feeble attempt to patch him up. They were doing what they knew from their experience.

Maybe it’s time to raise the bar in regards to what doctors, podiatrists, nurses, and other medical people should know. What’s taught in podiatry school to patch blisters? Is what they learn the best way? My guess is the trainers at the Australia Open were well-trained and good at what they do. Maybe in Chung’s case it was the perfect storm type of situation.

Maybe it’s also time to raise the bar on what athletes should know in regards to foot care and blister prevention and treatment. Many enter a race and expect someone to be there to patch their feet. That’s not fair to race directors and volunteers. Many races are required by law and insurance regulation to have medical people at their event or on stand-by. But that doesn’t mean that know how to patch feet. I have seen excellent patching done by volunteers who have taught themselves.

What do you think?

A Survey about Your Favorite Tapes

I have often shared information about different types of tape for blister prevention and blister patching. I have my favorites, but am always open to learning about new tapes.

When I first learned about taping, there were only a few commonly used tapes. There was duct tape, Elastikon, and white athletic tape. That was back in the 80s and 90s.

I remember the blister patching job on my feet one of the years I ran Western States. I left the Rucky Chucky aid station with a wad of gauze taped to the ball of my foot with white athletic tape that made it hard to walk or run. Several years later at the Gibson Ranch 72 Hour I had a duct tape patch between two toes.

Now things have changed. Elastikon is hardly ever used. Duct tape is still used by some. White athletic tape is not popular but some still use it. Micropore paper tape is popular. HypaFix (or Coverall) is fairly popular. Leukotape P has a good following. KinesioTex and other kinesiology tapes like RockTape, StrengthTape and KT tape have become very popular. Outside the United States, other tapes are often used too. For example, in the United States, HypaFix is the same as Coverall, but it’s also called Fixomull in other countries.

Sometimes certain tapes are used because of the conditions like heat, water, humidity, sand, and the length of the event. Other times tapes are used based on what’s available at an aid station.

So my question is, “What’s your favorite?”

I have a two-question survey that I would appreciate your participation in getting good data. The first question is What is your favorite tape for pretaping for blisters prevention? The second question is What is your favorite tape for blister patching?

There are only nine answers to choose from so the survey will take only a few minutes. The list of possible answers is the same for each question.

Here’s the link to take the survey: What’s Your Favorite Tape survey.

Thank you for helping compile the data. In several weeks. I’ll share the answers.

Finding the Right Combination

November 22, 2017 by · Leave a Comment
Filed under: blister care, Foot Care, Footcare, General, Health, Sports 

This is Part V in a series about blister formation and prevention. Below are links to the first four parts of the series.

Finding the Right Combination

Each athlete needs to find a blister prevention strategy that works for him or her. One may use a lubricant, another may use Zeasorb powder, and yet another may pretape his or her feet. Each may use one of many types and styles of socks. There are many combinations. Remember, the goal of all these components is to reduce shear stress by bone movement, pressure, friction, and moisture; increasing skin resiliency; and absorbing shear. A look at the image will show how the 5 Blister Formation Factors (the 2nd outermost circle) and the 13 Blister Prevention Components (the two inner circles) are related.

Five Circles 1

High-level views of the factors in blister formation and components in blister prevention
The legend for the inner circle: G=Gaiters T=Taping N=Nutrition and Hydration C=Shoe and Sock Changes I=Insoles and Orthotics L=Lacing A=Antiperspirants S=Skin Tougheners and Adherents

Five Circles 2


Try any of the suggestions and find those that work for you. Some will and some won’t. That’s OK, because it’s a process. You are gathering information that will help you now, and file away other information that may help you later.

At the 2017 Western States Endurance Run I treated many runners who had ignored my advice about Running a Wet 100 Mile Trail Run posted on my blog two weeks before the race.I gave advice based on my years of experience in working on feet in multi-day races around the world. Things like clean socks, powder and lubes made for wet conditions in drop bags. And carry the same in hydration packs. I gave proactive advice on caring for one’s feet. It seemed the majority of the runners I treated had not read my blog post. because more runners than usual had badly macerated feet. The did not take advantage of a few of the components mentioned above.

Here are two more examples of runners using blister prevention components in combination.

Ultrarunner Dave Scott claimed his feet are often “as soft as a baby’s bottom” after the 100-mile Western States Endurance Run. Dave found that he rarely had foot problems. He trimmed his toenails, used a small amount of petroleum jelly, and regularly changed his shoes and socks. That is what worked for him.

Ultrarunner Tim Twietmeyer has won the grueling 100-mile Western States Endurance Run five times while accumulating 25 silver belt buckles for finishes less than 24 hours. Over the years, in addition to running ultras, he has enjoyed fast packing in the California High Sierra. He has found the differences interesting.

A week before running a 100-mile trail ultra, Tim trimmed his toenails as short as possible. The morning of the run he coated his feet with lanolin to reduce friction, provide warmth if running in snow or through water, and make his skin more resilient to getting wrinkled. Then he pulled on a pair of Thorlos Ultrathin socks. His strategy is “that the more sock you wear, the more moisture close to the foot. The more moisture, the more blisters and skin problems.” He usually wore the same pair of shoes and socks the entire way. Tim acknowledges, “My feet don’t usually have problems, and when they do, I’m close enough to the end to gut it out.”

Tim found that fast packing affected his feet differently. When he hiked the John Muir Trail in 1992 (doing 210 miles in five days and 10 hours), his feet were trashed more than ever before. His group of five experienced ultrarunners averaged 14 hours per day on the rough trail. Tim remembers, “We covered the ground so fast that my feet swelled and I almost couldn’t get my shoes on the last day.” He used the same strategy of using lanolin and thin socks. Instead of running shoes, he chose lightweight hiking boots. Foot repair became the group’s daily ritual as the 40-mile days took their toll. They realized that “an important strategy for keeping our feet from getting any worse was to get that first piece of duct tape on in just the right spot and make it stick. If we did that, our feet held up pretty well.” By the end of the fifth day, the last piece of duct tape had been used on their feet. Tim’s

cardinal rule for fast packing is to “keep your feet dry.” That can be hard to do when fighting afternoon thunderstorms, but when your feet are wet too long, it’s only a matter of time before they blister. Whether running ultras or fast packing, Tim knows the importance of keeping his feet healthy, and he has experimented to find what works well for him.

Both Dave and Tim used a combination of components: skin care, socks, lubricants, taping, toenail care, and changes of shoes and socks in an effort to prevent blisters. Determine what foot problems you normally experience, study this book, and then begin the task of finding what works best for your feet.

We need to understand the importance of other elements that contribute to prevention. Proper strength training and conditioning will help make the foot and ankle stronger and more resistant to sprains and strains. Everything you put on or around your foot becomes related to how well your foot functions. Keep in mind that whatever you do, the aim should be to reduce shear, moisture,

The Components of Prevention

November 12, 2017 by · Leave a Comment
Filed under: blister care, Foot Care, Foot Care Products, General, Health, Sports 

This is Part IV in a series of posts about blisters, their formation, causes, and prevention. In this post we look at the 13 components of blister prevention – five major and 8 minor components. They all play a role and are important to understand.

Blister prevention takes place through a combination of 13 components. Five are the most major components: fit, socks, ENGO patches, lubricants, and powders. Eight others are minor but still important components: skin toughening agents, taping, insoles and orthotics, skin care and hydration, antiperspirants for the feet, gaiters, lacing, and changes of socks and shoes.

Within our shoes many things are happening, and everything is related in some way. Where something touches another, we have what we’ll call an interface. The basic interfaces are between the skin and sock, the sock and the insole, and the sock and the inside of the shoe. When you put tape on the skin, it adds two more, between the skin and tape, and the tape and the sock. Adding an ENGO patch adds two more. Since the tape and the ENGO patch are stuck to the skin and shoe respectively, the only interfaces we are concerned with are the tape and the sock, and the ENGO patch and the sock. The interface with the lowest COF determines or limits the magnitude of friction. If the tape loosens on the skin, another damaging interface is added.

The Five Major Components

We’ll start with the top circle comprised of fit, socks, ENGO patches, lubricants, and powders—the first line of defense against blisters. It’s important to remember that these five components and the eight from the next circle all work in some way to reduce shear distortion. They may increase skin resilience; reduce bone movement, pressure, friction, and moisture; absorb shear; or reduce the number of repetitions. Remember that the more you use shear-reducing or shear-absorbing materials in your shoes, the more you are taking that stressor off the skin.

  1. FIT comes first. You need to start with properly fitting shoes with a quality insole. No matter how well you tape, how good your socks are, or how good any other component is, if the shoes fit incorrectly, you will have problems. If your footwear is too loose, your feet will slide around, creating shear. If your footwear is too tight in certain areas, your feet will experience excessive pressure. Wearing too-loose or too-tight footwear will change the biomechanics of your foot strike, which in turn will affect your gait and throw off your whole stride and balance.
  2. SOCKS come in either single- or double-layer construction. Some singlelayer socks, particularly those without wicking properties, allow friction to develop between the feet and the socks, which in turn can create blisters. Double-layer socks allow the sock layers to move against each other, which reduces friction between the feet and the socks. Socks can also wick moisture away from the skin. Injinji toe socks give each toe its own sock.
  3. ENGO BLISTER PREVENTION PATCHES are effective at reducing shear distortion by reducing friction at the skin and sock–shoe interface. The patches are an alternative to taping.
  4. LUBRICANTS create a shield to reduce friction and protect skin that is in contact with socks during motion. This lubricant shield also reduces chafing.
  5. POWDERS reduce friction by reducing moisture on the skin, which in turn reduces friction between the feet and the socks.


Prevention Components

The 13 components of defense against blisters


Outer Circle: Fit, Socks, ENGO patches, Lubricants, and Powders.

Inner circle: G=Gaiters T=Taping N=Nutrition and Hydration C=Shoe and Sock Changes I=Insoles and Orthotics L=Lacing A=Antiperspirants S=Skin Tougheners and Adherents

The Eight Minor Components

Now, imagine another circle made up of eight components that play a strong supporting role in prevention—the second level of defense against blisters. This innermost circle is made up of skin toughening agents, taping, insoles and orthotics, skin care and proper hydration, antiperspirants for the feet, gaiters, lacing, and frequent sock and shoe changes. Each can contribute to the prevention of blisters and other problems. You could argue that these outer components should be identified as major components, and to some extent you may be right—some components may be more important for your feet than for mine. The trick is to determine what we each need to keep our feet healthy under the stresses of our particular sport. Let’s look at each component.

  1. SKIN TOUGHENING AGENTS form a coating to protect and toughen the skin. These products also help tape and blister patches adhere better to the skin and lead to a reduction in perspiration.
  2. TAPING provides a barrier between the skin and socks so friction is reduced. Proper taping adds an extra layer of skin (the tape) to the foot to prevent hot spots and blisters. Taping can also be a treatment if hot spots and blisters develop. ENGO patches can be an alternative to taping or compliment taping. Toe caps are silicone gel devices that go over the toes and absorb shear.
  3. INSOLES AND ORTHOTICS help maintain the foot in a functionally neutral position so arch and pressure problems are relieved. Some also have absorption qualities. Small pads for the feet may also help correct foot imbalances and pressure points. They can be bought over the counter or be custom made for your feet.
  4. SKIN CARE for the feet includes creams and lotions to smooth and soften dry and callused feet. This also includes good toenail care. Proper hydration can help reduce swelling of the feet so the occurrence of hot spots and blisters is reduced. These all contribute to skin resiliency.
  5. ANTIPERSPIRANTS for the feet help those with excessively sweaty feet by reducing the moisture that makes the feet more prone to blisters. It’s another help in skin resiliency.
  6. GAITERS provide protection against sand, dirt, rocks, and grit. These irritants cause friction, hot spots, and blisters as shoes and socks become dirty.
  7. SHOE LACES and boot laces often cause friction or pressure problems. Adjusting laces can relieve this friction and pressure and make footwear more comfortable.
  8. FREQUENT CHANGES OF SOCKS AND SHOES help keep the feet in good condition. Wet or moist socks can cause problems. Changing the socks also gives an opportunity to reapply either powder or lubricant and deal with any hot spots before they become blisters. Sometimes shoes are also changed as they become overly dirty or wet.

The next post will look at how we found the right combination of blister prevention components that will work for us.

Understanding the Five Factors in Blister Formation

November 2, 2017 by · Leave a Comment
Filed under: blister care, Foot Care, Footcare, General, Health, Sports 

Understanding the Five Factors in Blister Formation

This is Part III in a multi-part series on blister formation. This is a subject that still confuses many athletes. In this post, we look at the five factors that are the leading causes of blister formation.

For years, we thought blister formation was caused by heat, moisture, and friction. So, ever since the first edition, the image used to show this was a triangle with heat, moisture, and friction at its three sides. Everyone thought the three factors combined to make the skin more susceptible to blisters. That’s what was promoted in articles, running forums, and general discussion. It seemed to make sense.

Then we discovered shear, as you read in the previous Part II post. Shear encircles everything. The image shows a series of two concentric circles where shear is outside as the base on which everything else rests. The next circle contains the five factors that contribute to shear: skin resilience, bone movement, pressure, friction, and moisture. In the next post, we’ll look at the two inside additional circles: the first with the five major components of blister prevention and the innermost circle with the remaining eight minor components, which I will explain later. For now, we’ll look at the five factors that contribute to shear.

Blister formation

A view of the five factors in blister formation

1. Skin Resilience

Our skin is very resilient. However, repeated stressors to the skin, over time, can cause breakdown. The healing process can’t keep up with the ongoing trauma. This is why well-fitting shoes are important. Skin that is thin (like on the top of our feet) will abrade before it blisters, whereas thicker skin (like on the soles of our feet) is more likely to blister. We can make the skin on our feet more resilient by progressively increasing distance over time. This gradual increase of the frequency and magnitude of forces applied to the skin helps change the characteristics of the skin. Reducing calluses and using moisturizers also contributes to skin resiliency.

2. Bone Movement

As the bones in our feet move back and forth and up and down through the foot strike, and the overlaying skin remains stationary, the soft tissue layers in between stretch in a shearing motion. The more movement, relative to the skin surface, the more chance you’ll blister. When that happens, there is stretching and distortion between the inner tissues under the bone. Shoe fit is an important component in controlling bone movement. Changing your biomechanics is another way to work at reducing blister formation.

3. Pressure

Pressure is vertical force exerted against an object or surface. In this case pressure is the normal force of the foot through the foot strike. The heel comes down, the foot rolls forward onto the forefoot and off the toes. At all of these transitions, there is pressure downward, forward, and most likely side-to-side. Optimizing the fit of your footwear, correcting any biomechanical issues with an orthotic, and adding cushioning or padding can reduce pressure.

4. Friction

Mention the word friction to athletes and they most commonly think of rubbing. For instance, “My heel rubbed inside my shoe and created a blister.” It may help to know that the dictionary gives two definitions for friction. The one most people think about is the action of two surfaces rubbing against each other. Rubbing can cause abrasions to one or both surfaces, but not a blister. Forget about this definition as we talk about blisters. Let’s look at the second definition.

Scientifically, friction is defined as the force that resists one surface sliding against another. It’s easiest to view friction in one of two ways. When two surfaces slide easily against each other, we have a slippery connection—and low friction. When two surfaces resist movement against each other, we have a sticky connection—and high friction. Friction is required for shear to reach traumatic levels.

Rebecca Rushton of says it well: “There is high friction in your shoe. Surfaces are resisting movement against each other. When your skin is moist, your skin grips your sock; your sock grips your shoe. All three surfaces grip together so your foot doesn’t move around in your shoe. But with every step you take, your foot bones are moving under the skin. And while the skin is stuck the bones are moving back and forth. Everything in between is pulled and stretched. This pulling and stretching is what causes blisters. We call it shear.” Note: Rebecca wrote the forward to the 6th edition of Fixing Your Feet.

There is good friction and bad friction. High friction, as Rebecca described, is when things grip together. From this comes traction, which we need for the mechanical efficiency of our gait. Most friction is good, but when high friction causes blisters, it’s bad friction, and has to be managed—but only in that specific location. ENGO patches are an example of targeted management of friction. Now let’s look at the forces affecting friction, specifically the coefficient of friction.

4.a The Coefficient of Friction

The coefficient of friction (COF) describes the relationship between the force of friction and the normal force between two objects at which sliding is initiated. It is a number that represents the slipperiness or stickiness between two surfaces and is generally below 1.0. Within the shoe, the COF between the foot, sock, and insole can range from 0.5 to 0.9. In contrast the COF between a sock and a polished floor is around 0.2. The lower the number, the better the effectiveness in preventing blister formation.

Here’s an example. A runner may have damp feet, creating a moist condition. The COF in his case might be a 0.7. By moving away from the moist condition to either very dry feet or very wet feet, he might reduce his COF to 0.5. If his blister-causing threshold is 0.6, getting to 0.5 will reduce his chance of blistering. Moist skin is higher friction than dry or very wet skin, meaning it’s more susceptible to blistering.

Understanding the COF of materials is beneficial to knowing how shear starts and what we can do to reduce blistering. Managing the moisture on the skin, using different socks systems, and using ENGO patches are the easiest ways to reduce the COF. The COF of an ENGO patch is about 0.16 equally against a dry or wet sock, effectively reducing friction by 80%. Compare that to the COF of moleskin against a dry sock of 0.6 and a wet sock of 0.86. Again, the lower the number, the better the result.

5. Moisture

Moisture is the last factor. Increased moisture leads to an increase in friction. Beyond that, moisture does not cause blisters in any other way. Generally speaking, a lower COF is achieved with dry socks compared to wet. Some degree of moisture control can be gained with moisture-wicking socks, antiperspirants, powders, and some special lubricants. Our feet have approximately 250,000 sweat glands that can produce continuous moisture, without factoring in sweat produced though an increase in body temperature as we engage in physical activity. When active, most athletes have feet that are always damp from moisture. Moisture can also occur from stream crossings, rain, and puddles, as well as from pouring water over our heads to cool us down, which runs down our legs into our shoes.

Other Factors

There are three additional factors worth mentioning, but they are not important enough to warrant lengthy explanations or inclusion on the chart. The first is heat. Heat is not a factor in blister formation, but many athletes equate heat to causing blisters. Heat produces moisture as the feet sweat, leading to a higher COF and an increase in friction levels. But heat does not cause blisters in any other way. The second is repetition. We can minimize the chance of blisters by reducing repetitions. This can be done by shortening the length of your activity, reducing the level of intensity, and changing the frequency of your activity. But not many athletes will stop running or hiking—so there’s little point in talking about reducing repetitions.

The third factor is shear absorption. The less shear absorption in your footwear, the more pressure and friction your skin has to absorb—and that means more chance of blisters. Most of this is covered in cushioning components like socks and insoles as they work to reduce pressure and absorb shear.

The next blog post will look at the components of prevention.

Understanding Shear

This is part II of a series on blister formation and prevention. If you’ve missed the first post, I encourage yo to go back and read it to get a foundation on blisters. Here the link: Blister Formation.

In this part II, we’ll look at shear. For years we didn’t understand the concept of shear and its effect on blister formation. So let’s start with a story.

In Fixing Your Feet I tell the story of a runner at Badwater whose feet I patched. In short, he had run 90 miles of the 135-mile race, on pavement, in extreme heat. He had Elastikon tape on both balls of the feet. His feet were hurting to the point of quitting. I replaced the Elastikon tape with smoother kinesiology tape, which allowed movement between the tape and his sock, greatly reducing the shear movement between the layers of skin and the bones of his feet. I also added a large ENGO Blister Prevention Patch on each insole under the ball of each foot. By reducing the shear level, the runner was able to finish the race with less pain. Try to picture the following: as your foot moves through its foot strike, the bones of the foot move against the layers of underlying skin—then you apply a tape that is not smooth to the skin, pull on a sock, and finally put your foot inside a shoe. The tape sticks to the skin. As you run, the foot naturally moves a bit inside your shoes.

However, the sock cannot move freely against the coarseness of the tape. The sock and tape move as one, which stresses the outer layer of skin against the inner layers. The only movement is the shearing effect between the layers of skin.

That experience was the first time I made the connection to shear, although I didn’t know it by that name. All I knew is the stickiness at the sock–shoe interface, the tape–sock interface, and the tape–skin interface—and one, or all three, had created this major problem for the runner. I never forgot the story. His skin was stuck to the Elastikon tape, the coarse tape didn’t move against his sock, and the sock didn’t move against the shoe’s insole. With the smoother kinesiology tape and the new slipperiness between the tape and the sock, the coefficient of friction was reduced and in turn shear was reduced.

Shear is a new concept for most athletes, especially as it relates to blisters. Shear is defined as a strain in the structure of a substance when its layers are laterally shifted in relation to each other. Applying the definition to the above example, shear happened between the layers of skin as the bones of the foot moved through the foot strike. The internal layers of skin were connected. But those connections can break under the stress of shear and the cavity fills with fluid—and you have a blister.

To understand shear, try this. Place the tip of your index finger against the skin on the back of your hand. Keep it stuck to the same bit of skin while you move it back and forth while. See how your skin stretches? The skin on your hand has moved against the underlying bones. That is shear that causes blisters.

Note that nothing has rubbed against the skin. Your finger did not rub the skin. J. Martin Carlson, the founder of Tamarack Habilitation Technologies, has championed shear as the cause of blisters. Tamarack has a long history of providing innovative orthotic-prosthetic componentry and materials. Their focus on friction management, especially for amputees, has won them many awards and much recognition. This knowledge in turn led to the creation of a new product that can be applied to footwear to reduce high friction levels and, in turn, the shear that leads to blister formation: ENGO Blister Prevention Patches.

Shear in Action

After watching a video on Tamarack’s website, I understood more about shear in action. The video showed a cutaway on the heel area of a shoe, showing the sock and foot inside moving through a foot strike motion. In one video, the cutaway showed a sock and foot on an insole where there were high levels of friction. The sock and foot were distorted as they were held against the insole. It was as if they were stuck together. In another video, the sock and foot were on an insole with an ENGO patch underneath. No distortion occurred as the sock and foot moved easily through the foot strike, over the slippery surface of the ENGO patch.

It’s important to grasp how shear happens. As described above, shear results in distortion occurring between the skin and soft tissues underneath. This shear distortion is what causes blisters. The bones in our feet move back and forth as they move through each foot strike. When the skin at the bottom of the foot is stuck by high friction (stickiness) to the sock and shoe, the middle tissues are distorted. When this is repeated over and over, traumatic levels are reached and a blister forms. This distortion can happen anywhere on the foot: in an up-and down motion in the heel, the sides of the foot, and between toes; in a side-to-side motion at the ball of the foot, under the heels, and at the bottom of the toes; and in rotation as the foot moves through its foot strike. As we walk, run, and pivot in our shoes, the surface of our skin incurs a shearing force.

Certain amounts of shear are normal, and our feet can deal with a lot. However, with repeated traumatic levels of shear, blisters will develop. How much is too much? It varies from person to person, and some people are simply more blister-prone than others.

Part III will look at the five factors of blister formation.

Blister Formation

October 14, 2017 by · Leave a Comment
Filed under: blister care, Foot Care, Footwear Products, Health, Sports 

This is the first in a multi-part series on blister formation and prevention. Subsequent posts will focus on various part of the blister process. Too many people do not understand how blisters form, some even think they are a natural part of the running or hiking experience.

Blisters are the result of shear trauma to the skin. When running, every step is “repetitive loading” as the foot moves through the foot strike. The whole of the body’s weight is put on the skin and inner tissues, onto the bones and joints, up the leg, into the knees and hips, and into the pelvis and spine. For now, let’s focus on the foot. The skin can take a lot of repetitions without a problem, but once skin and tissue damage reaches a painful level, the trauma is escalating rapidly.

Repetitive loading has two components. The first is a vertical loading to the surface of the skin and by itself is relatively harmless. The second is a repetitive friction loading parallel to the surface of the skin. The two combine to create shear stresses within the skin. When these shear stresses exceed a certain level, micro tears begin to form within the third layer of tissue. As more repetition occurs, more micro tears appear and existing tears grow. These tears in the tissue form a cleft parallel to the skin’s surface. The cleft fills with serous fluid and a blister has formed—caused by shear stressors. This typically occurs in the stratum spinosum, the inner fourth layer of the epidermis that is the least resistant to shear.

If the blister is deep or traumatically stressed by continued running or hiking, the serous fluid may contain blood. When the serous fluid lifts the outer layer of epidermis, oxygen and nutrition to this layer is cut off and it becomes dead skin. This outer layer is easily burst. The fluid then drains and the skin loses its natural protective barrier. The underlying skin is raw and sensitive. At this point, the blister is most susceptible to infection.

Rebecca Rushton, an Australian podiatrist and the author of The Blister Prone Athlete’s Guide to Preventing Foot Blisters, has studied extensively about blister formation. She has identified four requirements for shear that cause foot blisters to form:

  1. Skin resilience: The skin on our feet is, by its very nature, susceptible to blister formation. Repeated gradual exposure to shear can improve the skin’s ability to withstand shear stress. Often times the skin is stressed by a sudden increase, or an increase over many days. Examples include increasing one’s mileage too quickly and doing more than normal in a multiday event.
  2. Moving bone: Bones within the foot move throughout the foot strike. The more they move relative to the skin’s surface, the higher the shear stress created, and the more likely you are to develop a blister. An example is the movement of the heel bone underneath the skin as it moves up and down in the shoe’s heel counter.
  3. Repetition: It’s the repetitions throughout the foot strike that increase the odds of a blister forming. An example is studies showing that runners in a multiday event blister more as the race progresses.
  4. Friction and normal force: The levels of friction and pressure determine the amount of shear that impacts the skin.

It’s worth talking about how blisters will deroof—when the stop layer of skin is torn off the top of the blister. Consider a back-of-the-heel blister. A blister has formed because the heel bone has moved up and down while the outer skin has remained fixed inside the sock and shoe. The shear stressors, as described previously, have caused the blister. With repeated levels of movement against the skin on the back of the heel, the skin can be rubbed over and over. This is what causes abrasions. When the forces that cause blisters combine with forces that cause abrasion, the skin is stretched past normal levels and is torn off.

In reality, some people are more blister-prone than others, irrespective of the amount of training and preparation. In spite of having done everything right, the shear strength of their skin is going to be lower than others—no matter what they do. They are simply blister-prone. For others, some of this has to do with the training that they do in preparation for races. It’s quite common at races to see lead runners come through aid stations without any blister problems. They typically have conditioned their feet through extensive training. But as the race progresses, the middle- and back-of-the-pack runners enter aid stations with a lot of blister problems. They typically have put fewer miles on their feet and, in some cases, have made poor choices about footwear and foot care.

This is the first in a multi-part series on blister formation and prevention. The material is extracted from Fixing Your Feet, 6th edition.

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