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 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.
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.