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

LEGEND

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 · 1 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 BlisterPrevention.com.au 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.

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