Dirty Old Socks

Posted February 1st, 2006

Many jokes and quips have been made about socks, but in reality, socks can make the difference between success and failure in an athletic event.
For most of us, socks represent a basic piece of athletic equipment. Many jokes and quips have been made about socks, but in reality, socks can make the difference between success and failure in an athletic event.
Foot damage and socks Fiber composition and sock construction can help protect feet from damaging forces that can cause bruised, painful, bloody toenails called subungual hematoma, acute infections called paronychia, or the chronic infections of fungal nails.
Today’s technology has invented socks that help prevent disabling blisters, painful corns, and even to some degree, burning callouses. All of these tissue injuries are caused by forces that are complex mixtures of ground reactive force and shearing force. Ground reactive forces can exceed three times the athlete’s body weight. Shearing forces are created by the pistoning movements of the foot within the shoe as the foot strikes and leaves the ground. The combination of ground reactive force and shearing force can be very harmful to foot tissue.
Biomechanical research and shoe technology have created athletic footwear that reduces and even controls some of these problems, but the sock remains the last layer of protection. Sock choice can be very important to the completion of an event without injury. This past summer I reported on the Vermont 100 ultra race and the disabilities associated with blisters (Blister Disaster, Sept/Oct 2005). These injuries, for the most part, were caused by the failure of socks to properly protect skin. In many instances, the failure was the athlete’s poor decision regarding choice of sock style or fiber, or the failure of the athlete to change socks in a timely fashion in adverse weather conditions.
How socks work Fiber composition and knit patterns are the working parts of socks. Fibers that absorb moisture are hydrophilic and those that shed moisture are hydrophobic. Cotton is hydrophilic. Cotton fibers can absorb three times that of acrylic and retain moisture fourteen times longer when exposed to air. This moisture must be dealt with to minimize skin damage.
During athletic activity, each foot can produce as much as one pint of fluid. Tests have shown that when socks become saturated, their fit and function changes. Cotton, the fiber best at absorption, will loose shape and bunch when wet. Cotton’s friction point also increases when wet. Combine these two factors and you have disabling blisters, or at the least, blisters that take all the fun out of the game.
During the 1980’s, the U.S. Army took socks seriously. They performed tests on marching infantry recruits. How long could one pair of socks be expected to perform before problems occurred? Which fibers produced the least problem? These questions were examined and soon cotton was no longer a contender. Fibers such as Coolmax and Acrylics filtered to the top of the “best performance” list. These hydrophobic fibers wick moisture from the skin and their friction points are actually reduced as they become wet. The reduced friction point factor is very important in minimizing skin injury. Early production of these socks were double layered, with the idea of eliminating blisters altogether, but the innovation failed to work. The double layered designed bunched in the shoe in long-distance events.
The Army studies also found that combining socks with shoes that have mesh uppers in the toe box greatly improved the wicking process.
The sock and shoe work together to help remove moisture from skin surfaces. Sock manufacturers moved quickly on all this new information and began producing socks designed for specific demands of various sports. However, little difference actually exists in sport activity demands, except for protection from cold. When the foot is in motion, it will begin to produce perspiration. It is part of the human body’s very complex thermal regulatory system. Hot moist feet will trigger a response that will help cool the body down. Women’s feet tend to be hotter then men’s. Women will often complain that their feet are too hot. They tend to gravitate to cooler, airier shoes. A study in Great Britain is currently underway regarding this. For now, I suggest female athletes use extra caution when choosing both socks and shoes.
My favorite socks: Cold weather protection demands wool. Wool will keep you warm when it is wet. Take snowshoeing for example. The body usually overheats and perspires in an attempt to regulate core temperature. Feet become moist in the process. During rest or cool-down stages of a trek, you must protect them from thermal damage. Wool will do the job. I always suggest Smartwool because the weave pattern also helps wick moisture away from feet. Smartwool socks are easy to find and come in various thicknesses for degrees of desired protection. I am very impressed with made-in-Vermont “Darn Tough” socks. My wife, Louise, and I have been performing field tests on our snowy snowshoe treks. Darn Tough socks are comfortable and their performance is as good as Smartwool’s. Coolmax is my favorite sock for all other sport activities and using Coolmax as a liner under Darn Tough or Smartwool socks will give you the thermal protection and wicking advantage you need.

Rob Rinaldi DPM

Robert Rinaldi is a board-certified podiatrist and podiatric surgeon at the Gifford Medical Center in Randolph, VT. He is a fellow and a founding member of the American Academy of Podiatric Sports Medicine, and a podiatric consultant to the Dartmouth College track and cross-country teams. He is a former nationally ranked long-distance runner, having competed in 25 world-class marathons. You can reach him at Gifford Sports Medicine and Surgery Clinics in Randolph, VT, or at the Sharon Health Clinic in Sharon, VT, 802-728-2490 or 802-763-8000 or at rrinaldi@giffordmed.org.