U.S. Army Study Confirms Performance Benefits of CoolMax® Socks

Socks made of DuPont certified CoolMax® will soon be adopted by the U.S. Military for official dress socks and liners for boots. This decision is the result of testing conducted by the U.S. Army Research Institute of Environmental Medicine. The study, focusing on the impact of sock systems on the frequency and severity of blister injury in a Marine recruit population, proved that DuPont certified CoolMax® socks, constructed of DuPont proprietary tetra-channel fibers, provide the most comfort under the most strenuous conditions.

According to the U.S. Military, blisters have plagued the feet of infantry forces and reduced the combat effectiveness of military units throughout history. The purpose of the study was to test the ability of a prototype sock system to reduce blister incidence.

Testing took place at the Marine Corps Recruit Depot in Parris Island, S.C., one of the most challenging training facilities for new recruits, from May to August, 1992. Male Marine recruits undergoing basic training served as subjects of the study.

The participating 357 recruits were separated into three groups. The first wore the standard issue sock made of a blend of wool, cotton, nylon and spandex. The second group wore the standard sock with a thin inner sock made of 80 percent DuPont tetra-channel fibers, commercially known as CoolMax, knit with nylon. The third group wore the same CoolMax® inner sock with a prototype outer sock made of wool and polypropylene.

Temperatures at Parris Island averaged between 81 and 93 degrees during the 12-week testing period, during which recruits went on 5, 8 and 10-mile road marches. After rigorous wear in the hot and humid conditions, recruits wearing the prototype outer sock with the CoolMax® liner experienced a 300 percent reduction in blisters, the skin infection cellulitis and the associated limited duty time as a result of these foot conditions compared with those wearing only the standard issue sock without the liner. In fact, both groups wearing the CoolMax® liners suffered significantly fewer blisters compared to the other recruits. "We found that the CoolMax® liner sock improved foot conditions when worn with either outer sock," says Dr. Murray Hamlet, director of the Army Research Institute of Environmental Medicine.

For the blisters and cellulitis that did occur, the study found that the recruits who wore sock systems featuring the CoolMax® liners experienced only half the number of sick calls as those recruits who wore the standard sock system.

"Certified CoolMax® is made from premium tetra-channel fibers that regulate the body's temperature by moving moisture away from the skin through the fabric's surface where it quickly evaporates," explains Tom Beck, CoolMax® technical manager. "This unique combination of wicking and evaporation keeps the foot dry and comfortable and eliminates one of the major components necessary for blister formation. For soldiers who undergo rigorous training, dry feet are essential for peak performance."

While the Marine recruit study was strictly objective, focusing on the physical conditions of recruits' feet, the U.S. Army Research Institute also collected subjective comments about CoolMax® from Marine drill instructors who wore CoolMax® liners. According to Dr. Hamlet, "The instructors said that they did not end up with 'fire feet', the hot, jabbing, prickly feeling they often get after marching on black pavement, when they wore the liners. "Other comments regarding CoolMax® liners, he notes, included, "Where have you been all my life?" and "It's like wearing air-conditioning on my feet."

As a result of the official study, the U.S. Military, including the Army, Navy and Marines, is instituting an official sock program, specifying the proprietary DuPont yarns for liner socks and dress socks. The socks will be knit from DuPont tetra-channel yarn and textured nylon. According to the U.S. Military, recruits that suffer fewer blisters in the early portion of their training may adapt and train more effectively. Further, military units whose feet may not be adapted to extensive march training and are, therefore, more prone to blisters may be called to perform missions. The U.S. Military believes that these units may especially benefit from wearing certified CoolMax® socks.

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