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.

Feet at Western States

July 2, 2017 by · 2 Comments
Filed under: blister care, Foot Care, Footcare, General, Health 

On June 12 I wrote a blog post Running a Wet 100 Mile Trail Run.

On June 24, I found out many runners ignored my advice, to their detriment. Maybe they didn’t read it, or didn’t see it, or simply read it and ignored it.

A typical year at WS has our foot care team at Michigan Bluff lancing and patching a goodly number of blisters. On toes, heels, ball of the foot, arches, and more. Maybe 50 to 75 blisters. Maybe more. We really don’t count.

This year I lanced and patched one blister. Yes, that’s right – ONE.

But this was not a typical year at WS. Instead of dry conditions, there were miles of snow, and mud, combined with heat so runners soaked themselves in streams and poured water over their hears and down into their shoes.

Maceration WS100I predicted the outcome. Maceration.

Runners came in to see us complaining of blisters and were surprised when we told them there were none. Just macerated feet.

So we powdered their feet, asked them if they had dry socks. And hopefully, dry shoes. We fixed and changed what we could and sent them on their way – wishing them well.

Were this year’s conditions not known in advance? I don’t think so. Runners and crews knew of the record snowpack. They should have expected water and wet conditions. For whatever reason, many ignored the warnings.

It’s unfortunate that so many runners jeopardized their opportunity for a buckle and a successful race on something that was manageable.

I’d love to hear from runners about what they thought. Send me an email.

In the meantime, click the link and read Running a Wet 100 Mile Trail Run.

Running a Wet 100 Mile Trail Run

In less than two weeks is the running of the Western States 100-Mile Endurance Run. I will be at the 55.7-mile Michigan Bluff aid station, along with Tonya Olson and others on the medical team. Our aim is to make sure you are healthy to continue on towards Placer High School and a good finish.

For the past six years, the mountains have been dry and the trails dusty. Feet get caked with dirt. Blisters are caused by the dust and dirt as an irritant inside shoes and socks.

2011 was the last snow year. I have looked a bit online and am unclear on snow conditions this year. But this much I am certain, there will be snow and feet will be wet. How much snow remains to be seen.

I am 100% certain that runners will have long sections of wet trail, either from the snow, snow run off, water on the trail, and stream crossings. That equals miles of running with wet feet. I’m also 100% certain that we’ll have lots of wet feet, blisters, and maceration. In fact maceration could easily be a bigger problem than blisters. Don’t forget to avoid pouring water over your head where it will run down your legs into your shoes, contributing to maceration. Lean forward rather then standing straight up.

A blister can be lanced and taped, and runners can continue without to many issues. Maceration is a different story. Once your feet are macerated – the skin shriveled like a prune, there is no quick fix.

With prolonged exposure, the skin on your feet goes through four stages as the maceration progresses to severe cracks and tears in the skin—that can be race ending. As the skin on your feet moves through the four stages, the skin folds over on itself and can crack or tear. This can be painful. Many runners come into aid stations complaining of bad blisters only to be told they don’t have any – it’s severe maceration.

I expanded the section on maceration in the 6th edition of Fixing Your Feet. Starting on page 188, are 12 pages with sections about Cold and Wet, Maceration, Trench Foot and Chilblains, Frostbite, and Snow and Ice. Included are tips and products to help with those conditions. If you have a copy, read the sections – and have you crew read them also. On page 101 is a section on High-Technology Oversocks like SealSkinz and Hanz, Serius, and eZeefit waterproof type socks. Another sock worth mentioning is ArmaSkin socks, which is used as a sock liner and fits tightly against your feet. They would be my choice for a wet race. I’d also wear gaiters to keep snow, dirt, and grit out of my shoes.

As far as skin preparation, here’s what I would do – expecting wet feet. My drop bags would have clean socks, small containers or baggies with powder to help dry wet skin, and container or tubes of any of the following: RunGoo, Trail Toes, Desitin Maximum Strength Original Paste, Boudreaux’s Butt Paste, or a strong zinc oxide paste. I’d also carry some in my hydration pack. I would apply a liberal coating of one of these from toes to up the heels and then roll my socks on. Rolling socks on will help prevent smearing and thinning the paste on areas of the feet.

Since proactive care is better than reactive, I’d check my feet at most aid stations, adding paste as necessary. If my feet were feeling bad at an aid station, I’d apply some powder to help dry the skin, and have some food while letting the powder do its job. Then apply more paste and clean socks. If your feet are badly macerated, it will take drying them, coating them with powder, and rubbing it in and letting it sit for a while, then stripping off the powder and adding more of your choice of paste. That may easily mean 15 minutes or more. If you don’t take care of macerated feet, they’ll get worse over time, requiring more care and longer time – and there may come a point when it’s irreversible in the time you have.

The time you take in aid stations does add up and it can quickly erase any time cushion you may have to finish within an allotted time. But skip quality care, rush too fast, ship hydration or eating, and you’ll pay the cost.

Remember your first line of defense should be your crew. They should know what you want for foot care and how to do it correctly. There aren’t enough medical people to take care of everyone’s feet and we may be busy with others, adding more time to your aid station visit.

Yes, as I said earlier, I will be at Michigan Bluff and Tonya and I will do our best to help you. But heed my warning. We cannot work miracles when you have failed to take care of your feet from the start. In the same way we cannot take away the pain and problems with black toenails and toe blisters caused by your not trimming your toenails, we cannot repair badly macerated feet when you have not tried steps to control the maceration.

I ran Western States in the late 80s and one thing I learned is the outcome of the race in your hands. Whether is your training, conditioning, choice of footwear, choices of food, what’s in your head, your choice of crew – lots of things affect your race. I encourage you to take the time necessary to care for your feet.

Don’t Do This to Your Feet!

July 17, 2016 by · Leave a Comment
Filed under: blister care, Foot Care, Footcare, Footwear, Health, Sports 

Over the next few days, over 90 ultra runners will test themselves at the Badwater Ultramarathon in California’s Death Vally. 135 miles. Extreme heat, scorching roads, sand, wind, hot winds, and then at the finish line – much colder temperatures. I’ll be there to help with runner’s foot care issues, working with Denise Jones.

I decided to rerun this blog post from 2010. It describes an issue that can harm a runner, and can happen when time is not taken to repair small blisters before they become large, and then huge.

Here’s the post from July 2010.

This was a good week. Badwater in Death Valley always is. Fit runners, great crews, fantastic scenery through the harsh reality of Death Valley – and for me, lots of feet needing care.

For the most part, things were pretty normal. Blisters and more blisters. A great case of severe capillaritis (heat rash) on one runner’s ankles. Ugly toenails. Stinky feet. And more. Lots to like for someone who does foot care.

At the closing ceremony, I noticed Monica, a runner from Brazil, was favoring her right heel. I had met her several years earlier at a previous Badwater when I patched her feet at the 40-mile mark. This year, she finished her 2nd Badwater and that was important. However, she had not come in for help.

She should have.

After the awards ceremony, Denise Jones came and told me I had to see this blister. She talked as if it was really a great find. Denise, as the Badwater Blister Queen, has seen everything and it takes quite a bit to faze her. This blister did. And yes, it was good.

What started as a small blister, one that could have been treated to prevent it from getting bigger, was now an enormous blood blister. The image shows you the size.

An enormous blood blister

An enormous blood blister

There were several issues we had to consider. First and foremost, Monica is a diabetic. This makes foot care a huge issue because any foot infection suddenly becomes a huge health issue. Secondly, the size of this blister, filled with blood, would make it difficult to patch. As always, blood-filled blisters must be managed with care.

We debated the issues and gave Monica advice on how to take care of the blister for her trip home. We advised frequent soaks in warm/hot water with Epson salts and sticking to sandals or other open heel footwear.

What I want to emphasize here is that this never should have reached the size it was and worse yet, filled with blood. For those wondering, a blood blister is bad because, once opened or torn, it can introduce infection into the circularity system if not kept clean.

I wish Monica had taken care of this earlier. She may have never mentioned it to her crew. At any rate, what could have been easily treated now became a huge issue.

It’s a good lesson on not allowing small problems to become large problems. In other words, “Don’t do this to your feet.”

Thru-Hikers Feet – an Update

July 13, 2016 by · Leave a Comment
Filed under: blister care, Foot Care, Footcare, Health 

This is an update to my blog post of May 28, A Thru-Hikers Story About Feet. The thru-hiker is Tami and she is still hiking the PCT.

When possible I love to share people’s before and after stories with their feet.

Her story was interesting because she was having huge issues with her feet. I shared three pictures that she sent me, which shows the damage to her skin. I’d suggest going back to read the first part of her story and seeing the pictures. It’s important because it put today’s blog post update in a real-life perspective.

Tami wrote:

“I just wanted to drop you a follow up line and let you know that my feet have never been better thanks to you! I just walked 600 miles (trudging over 20 miles per day in the High Sierra on rough rock during dehydrating heat spells carrying an extremely heavy pack complete with bear canister…yes this is a run-on sentence but I can’t help myself) using your preemptive taping methods and tincture of benzoin for toughening and I didn’t get one single blister! This is a huge breakthrough for me and I’m giving acknowledgements to your book and your suggestions everywhere I can- you truly are helping me hike the Pacific Crest Trail.

“Yes, I’m still hiking and super in tune with these feet. Every tiny hot spot or slight discomfort makes me stop and evaluate everything. Thanks for the reminder to not get complacent, it seems like my feet are tough, but it wasn’t too long ago that I was disabled to due horrible blisters.

“I thought my foot issues would be putting the cabosh on my plans, but here I am with happy feet! I met a girl on a bus who was limping around with blister pain and pulled out my foot kit for her to look at. She took notes, jotting everything down including your book title. These are hard lessons learned, but then again, I never seem to do anything the easy way. Thanks so much.”

So what do we learn here? We see that there is hope. It shows that athletes can survive and find help and solutions for their foot issues. Whether you are a thru-hiker, like Tami, an ultramarathoner, marathoner, walker, adventure racer, or anything else, you don’t have to quit because of your feet. Tami was smart and reached out for help – and was willing to put in the effort to learn what to do and what her feet needed.

You can do the same thing.

12 Foot Care Tips for Success at 100’s

June 18, 2016 by · 4 Comments
Filed under: blister care, Foot Care, Foot Care Products, Footwear, toenails 

Next week is the Western States 100 Mile Endurance Run and all the fun and hoopla that goes with it. I ran the race from 1985 – 1989 with a best time of 24:32. It was a challenge but I had fun every year. Ever since then I have been associated with the run in some capacity and for the last 16 or so years have provided foot care help at an aid station or two and the finish line. In that time I have seen a lot of runners come through aid stations needing foot care.

Feet at the finish line of Western States

Feet at the finish line of Western States

This year I decided to make a list of my top 12 foot care tips for success at 100’s – whether Western States or any other 100-mile run. You don’t want feet like in this picture.

  1. Make sure your shoes fit. That means a bit of room in the toe box and good grip in the heel. It also means that the shoes are in good shape.
  2. Make sure you wear good socks. That means no cotton, but only moisture wicking or water-hating socks. If you are prone to toe blisters, consider Injinji toe socks.
  3. Trim your toenails short and then file them smooth so when you run your finger over the tip of the toe, you don’t feel any rough edges or points. This goes for thick toenails too – file them down.
  4. Reduce your calluses with a callus file and moisture creams. Trust me, you don’t want blisters under calluses.
  5. Wear gaiters over the top of your socks and shoes. This keeps dust and grip from going down inside the shoes and inside your socks. Understand though that the mesh in today’s trail shoes does allow dirt and grits inside the toe box, even with gaiters.
  6. Use a high-quality lubricant like SportsShield, Sportslick, RunGoo, Trail Toes, or ChafeX. Do not use Vaseline.
  7. Know how to treat a hot spot and blister between aid stations – and carry a small kit in your hydration pack. Early care is better than waiting until a blister has formed or until the blister has popped and its roof torn off.
  8. Just as you have trained by running and conditioning, you need to know what your feet need to stay healthy and blister-free during the race. Just as you have learned what foods you can tolerate during a race and during the heat, you need to be prepared for foot care problems. Your feet are your responsibility.
  9. Make sure you have a well-stocked foot care kit(s) with your crew and they know, in advance, how to care for your feet. Trailside, at an aid station, is not the time to learn or to train them what you like done.
  10. When you pour water over your head and body to cool off, lean forward to avoid water running down your legs and in your shoes. Getting wet feet or waterlogged socks can lead to maceration very fast.
  11. Consider using RunGoo or Desitin Maximum Strength Original Paste liberally on your feet and toes to control moisture from excessive sweat, stream crossings, snow melt, and water poured over your head that runs down into your shoes. Reapply at aid stations. Maceration can quickly lead to skin folds, tender feet, skin tears, and blisters.
  12. Finally, DO NOT assume that every aid station has people trained in foot care or have the supplies necessary to treat your feet. If you have a crew, have them work on your feet. Many times the medical personnel are backed up or dealing with more serious medical emergencies. And, truth be told, blister are not a medical emergency. Heat stroke, heat exhaustion, dehydration, and the like are more serious than blisters.

Every year I am amazed at the number of runners who are ill prepared. They put extra socks in their drop bags – that have holes in them. The have open Athletes foot sores between their toes. Their shoes are shot and should have been replaced. They have not done good toenail care. They have thick calluses. They start the race with old unhealed blisters. Their shoes don’t fit. They wear full-length compression socks and then are amazed when we can’t get them off at the aid station to work on their feet. Tight fitting compression socks may feel good but are almost impossible to get off and even worse to get back on over patched feet.

While medical people will always try to help you, we can’t work miracles with your feet when you have neglected caring for them from the start. Again, your feet are your responsibility.

Blister Repair – Your Way or Their Way?

March 7, 2015 by · 1 Comment
Filed under: blister care, Foot Care, Health, Sports 

One of my goals is to educate athletes about good foot care techniques. You may recall blog posts where I stress the importance of knowing how to do foot care and importantly, to know what’s best for your feet.

I recently received an email from Rob, asking for some advice. Here’s Rob’s email:

“I have been running a modest 30 miles a week for a few years. Last weekend we attended a tennis camp and during the first night of drills during ball pick up (not during a drill or competitive play) another player smacked a ball in to the arch of my foot from a shot distance away causing severe pain. I played through the pain and the next morning I asked the trainer to tape up my bruised arch, which she did. I played all day and at the end of the day there was a blister in the center of my foot between the taped and un-taped area.

“I went back to the trainer in the morning and she created a donut shaped pad about a 1/4-inch thick and taped it to my foot. I took out my shoe arch supports and played for another 1/2 day in a bit of pain. When I took off the shoe, sock, and bandage and pad I found that the blister had filled with liquid to the size of the donut hole – now a huge blister about the size of a silver dollar and 1/4-inch thick. The camp staff took pictures of the biggest tennis-related blister they had seen.

“I went back to the trainer at the college and she drained about half of the liquid out of the blister and we decided I was done playing tennis for the rest of the camp. I’m not sure going to the trainer really helped and I probably should have had your book along as reference and taped myself up. Now I am back home and have a huge blister on the bottom of my foot.”

This is a case where the trainer patched Rob’s blister the best way she knew how. It was an “old-school” patch job. A piece of moleskin cut in a donut shape with a hole in the middle for the blister. There may have been Vaseline on the center, and then tape or gauze over the top.

The problem with this old-school method is that it adds bulk to the foot – that can easily alter the person’s gait. This gait change can lead to further problems. At the same time, the patch can cause irritation, expanding the original blister or leading to new blisters.

Rob’s experience shows there is a long ways to go to get everyone up to speed about good blister care. I’d bet that if Rob had been prepared, he could have done a better job then the trained did. It’s hard to go everywhere with a blister patch kit in hand, but here’s my recommendation. Make up several simple kits and put them in Zip-Lock bags and stash one in your car and another in your gear bag. Fill the kits with your choices of blister tapes and patches. Then of course, make sure you know the best way to patch any blisters that may develop.

This post is from July 2102, but is important for athletes to understand.

Typical Heel Blister Problems

January 12, 2015 by · 4 Comments
Filed under: blister care, Foot Care, Footwear, Footwear Products 

Heel blisters are quite common – although they shouldn’t be.

Feet in the Jungle Marathon

Heels in the Jungle Marathon

Today’s post shows one participant’s feet at the 2014 Amazon Jungle Marathon.

If you look closely at this picture, you’ll see two heel blisters, both on the outside of the runner’s feet. The right foot blister is large but is not blood-filled. The blister on the left heel, however, is very large and filled with a large amount of blood.

It’s easy to think these are normal blisters – but their size makes they abnormal.

In my experience, heel blisters are caused by the constant shear when either 1) the heel is moving up and down inside the shoes’ heel, or 2) by the constant movement at the place where the shoe’s insole touches the inside of the shoe. Over the years, the majority of heel blisters have been the latter. One of the characteristics of this “insole/shoe junction” blister is that they often are flat across the bottom. The blister starts at the point where the insole’s edge at the side of the heel touches the inside of the shoe. That’s what makes the flat line at the bottom. Then the blister forms upward as the fluid forms and it grows. Given enough time and movement, you’ll get blood inside.


These are relatively simple to patch. The skin must be cleaned with alcohol wipes, and then the blister can be lanced and drained. Depending on the size of the blister, you’ll need to apply some type of blister patch. The bottom line is that you need to have something over the blister to protect the skin and prevent the top layer of skin from tearing off. For these, I would use strips of kinesiology tape (my preference is either StrengthTape or RockTape H2O) with antibiotic ointment over the blister to keep the tape from sticking to the skin. The larger the blister, the harder these are to patch but it can be done.


You are better off to prevent these blisters in the first place.

Start with the fit. Make sure your shoes hold your heels in place with just a little movement.

Check your shoes and insoles for rough and/or thick edges at the inside and outside of each heel. Side blisters are much more common than the back of the heel. If the insole has a large thick edge, replace them. If the shoe’s fabric is worn into a hole, you are due for new shoes. Under the fabric is generally a plastic edge of the shoe’s heel counter – the plastic that curves around the heel from side to side.

Engo Blister Prevention Patches are perfect for to help prevent these types of blisters. These patches are super slick. Either the small or large oval can be applied to the inside of the shoe and cover the offending edge of the insole/shoe junction. Clean the inside of the shoe and insole first. I work the patch with my fingers to form a curve to fit with area I need to cover. Then remove the backing and apply the center of the patch first and then push the top and bottom of the patch into place. Rub it a bit to assure adherence.

A Survey About Feet From The 2012 Amazon Jungle Marathon

Vicky Kypta is the Medical Team Manager for the Jungle Marathon, which starts October 6 in the Amazon in Brazil. Last year she did an informal survey of the participants and the results are interesting. The race lasts seven days and goes through the jungle on pre-existing paths, trails, and tracks with natural obstacles to pass including streams and shallow rivers. This leads to feet that are constantly wet.

Jungle Marathon foot care

Jungle Marathon foot care

This is the race that I will be at in a few days.

Vicky shared the results of the questionnaire and commented it was quite interesting, although the sample group was quite small. There were about 30 participants.

Here are some of the findings:

  • 77% of the respondents wore Injinji socks
  • 100% of those NOT wearing Injinji sock got blisters
  • 46% of those wearing Injinji sock got blisters: out of those 50% were on the balls of the foot and 50% were on the toes. Those who had blisters on their toes all wore shoes in their normal size.

Out of those with no blisters:

  • 100% wore Injinji socks
  • 100% wore shoes one size larger
  • 75% applied some form of anti-friction compound to their feet; i.e. Body Glide, 2nd Skin or Zinc Oxide cream
  • 75% pre-taped problem areas or hotspots

I find this interesting and wonder what we will find with the 78 participants next week. The Jungle Marathons are well run and the staff tells runners to train with wet feet. They have found this results in less foot problems.

The results are striking in several areas (remember this is a seven day stage race):

  1. All the runners who did not get blisters wore Injinji socks and shoes a full size larger than their normal shoes
  2. All the runners who did not wear Injinji socks got blisters
  3. Runners wearing their normal size shoes all got toe blisters
  4. The majority of blisters were on the forefoot and toes

Over the past 17 years, I have worked a lot of ultramarathons and multi-day stage races. I can honestly say that overall, feet have improved. More runners are prepared and know how to manage their feet.

When I return, I will share what we found at this year’s Amazon Jungle Marathon.

Moisture on Your Feet – Moist, Very Wet or Very Dry

September 22, 2013 by · 1 Comment
Filed under: blister care, Foot Care, Health, Sports, Travel 

Back in May I posted an article about Training With Wet Feet. My being invited to work on the medical team at the Jungle Marathons in Vietnam and the Amazon prompted the article. While the Vietnam race had to be cancelled, the Amazon race is happening – in a bit over two weeks.

As I wrote in that article, it was long felt the best way to manage your feet was to keep them as dry as possible. This was more and more evident as Denise Jones and I worked the Badwater Ultramarathon in the heat of Death Valley each July. Runners who kept their feet dry typically finished better than those who had wet feet. This was also based on our experiences at Western States and other events.

Then came the invite to help at the Jungle Marathons.

The Jungle Marathons are run by Race Director Shirley Thompson and the Medical Team Manager is Vicky Kypta. They found their runners had a better race when they trained with wet feet. As part of their instructions to their race participants, they stress the importance of training with wet feet.

The reason for this is the Jungle Marathons are wet. Very wet is typical in the jungle. Whether through rivers or streams, the Amazon is full of water.

When I am helping runners at the race in early October, I will be closely monitoring the condition of their feet. I expect runners will use lubricants and other products to control the moisture, or powder, socks, well-draining shoes, and maybe a few home-grown tricks.

Over the past few months, I have shared some of the findings by Rebecca Rushton, a podiatrist from Australia. In her Blister Prevention Report, she talks about managing moisture control. She supports her report with studies from medical and other professional journals. What she found through the studies is that you could reduce the incidence of blisters by keeping the skin either very dry or very wet.

Rebecca writes that, “… the very high or very low skin moisture strategies aim to reduce the coefficient of friction value between the sock and the skin to below blister-causing levels.”

The Coefficient of Friction

The coefficient of friction (COF) is the number that represents the slipperiness or stickiness between two surfaces. According to studies, this number is generally below 1.0. Inside the shoe, the COF between the foot’s skin, and the sock and insole can range from 0.5 and 0.9. Compare this to the COF between a sock and a polished floor – about 0.2.

In Rushton’s report, she illustrates this with an example of a runner whose feet sweat a lot. His socks become damp, creating a moist condition. The COF in this case might be 0.7. By moving away from a moist condition to either very dry or very wet, the runner might reduce the COF to 0.5. If the runner’s blister-causing threshold is 0.6, getting to 0.5 will reduce his chances of blistering. Reducing the COF between your skin and socks/insole combination is important to having healthy feet.

Moist Skin

Moist skin produces higher friction than very dry or very wet skin. Whether skin is dry and becomes moist through sweat or through a water moisture source, or is very wet and becomes moist through heat or simply drying out, when it hits this middle stage, it becomes more susceptible to blistering.

Very Dry Skin

Drying the skin can be done with powders, antiperspirants or other drying agents, used by themselves or in conjunction with moisture control socks. Keeping the skin very dry is tough because our feet sweat naturally. Humid or hot conditions can also make it hard to keep the skin dry. Dumping water over your head to cool yourself can result in water running down your legs into your shoes – defeating your efforts to keep your feet dry. Airing your feet with shoes and socks off can help. If you use powders, make sure it is high quality and does not cake, which can be an irritant. When counting on any of these methods to keep your skin dry, you mush also have shoes that allow moisture to escape. That may include shoes with mesh uppers and drain holes in the arches and heels.

Very Wet Skin

Increasing skin moisture leads to very wet, lubricated skin that reduces the skin’s coefficient of friction. This can be through the use of a lubricant and or by simply having wet feet. The thing to remember is that over time, 1-3 hours, friction will increase as the lubricant is absorbed into the socks – so ongoing application is required.

Amazon Wet Foot

Amazon Wet Foot

Remember too what happens to your skin when you spend too much time in the water. It becomes weaker and less able to resist trauma on wrinkly skin. In extreme cases, the skin can fold over on itself and split. Severe maceration can be painful and athletes say it feel like a giant blister on the bottom of their feet.

In the Amazon Jungle Marathon, the trick will be to dry the feet at the end of each day’s stage. Because the feet will be wet during much of each day’s stage, the runners will have to find the balance between very dry and very wet, avoiding moist as much as possible.

Here’s some advice from my previous post about training with wet feet.

As said earlier, stop and deal with any hot spots as soon as you feel them. Check for folds in your socks, friction from dirt or sand, pressure inside your shoes – and get rid of these irritants. Lube the area or apply a piece of tape or blister prevention patch to help. This may seem like common sense, but many people ignore this simple step.

At the end of each day’s stage, remove your wet shoes and socks, dry your feet and air them as much as possible. If your feet have tape on them, remove the tape to dry the skin underneath. Wear sandals or Crocs around camp to keep your feet away from the wet ground and dirt and sand. Walking around barefoot will often aggravate wet, cold, and soft macerated skin. Later in the day or the next morning, re-tape your feet and patch any blisters.

Rest assured that I will write about how everyone’s feet held up in the wet Amazon jungle.

Credit is due to Rebecca Rushton for her Blister Prevention Report. Her website is Blister Prevention. Check out her website and sign up for her newsletter and free reports.

Here is the link to the Jungle Marathon Amazon.

If you want to read more, check out this article I did in November 2012 about Stuart Crispin who completed the race in Vibram FiveFingers.

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