Blisters and Other Skin Injuries
Friction blisters are among the most common foot injuries affecting the athlete. Blisters on the feet are even more prevalent and debilitating in military recruits. A study performed on 357 marine recruits at Parris Island, South Carolina, revealed a 69% prevalence of blisters during a four-month period of training. Blisters serious enough to warrant medical evaluation at sick call occurred in 24.4% of all trainees. It has been estimated that over 5,000 Basic Trainees at Lackland Air Force Base were treated for friction blisters during one calendar year in 1990.
Factors necessary for friction blisters are shear force, pressure and moderate levels of moisture. All of these forces can be mitigated by a proper sock system.
Herring and Richie investigated the role of fiber and sock construction techniques in the prevention of blisters on the feet of running athletes. Their findings demonstrated that acrylic fiber socks will have less blisters and smaller blisters than cotton fiber socks. In addition, athletes were able to determine a drier foot with acrylic socks compared to cotton.
These findings were significant only when socks were constructed with dense terry padding rather than in generic "cushion-sole" socks.
Plagued with ever-increasing frequency of blisters, the United States Military conducted three randomized prospective studies on various sock systems. The standard military issue sock is a 50% cotton and 50% wool cushion-sole sock. The three studies attempted to compare newer fiber construction techniques and double-layer technology to reduce blister frequencies.
In a study of 357 marine recruits on Parris Island, South Carolina in 1992, the use of a CoolMax® liner with a heavily padded terry design outer sock using a wool/polypropylene blend significantly reduced blisters compared to a single layer sock (40% vs. 69%). Adding a CoolMax® liner to the standard sock significantly reduced sick call visits (24.4% standard vs. 9.4% standard with liner).
Another study of 1,079 soldiers in 1993 tested five sock systems on blister frequency and acceptability by soldiers. Synthetic fiber socks significantly outperformed the standard wool sock. Adding a CoolMax® liner to the wool sock significantly reduced blisters. When comparing single, extra-thick acrylic padded socks to double layer sock-systems, the double-layer system was superior owing to the shielding of the open terry loops from the skin surface and the movement interface created by the double-layer system. Three other military studies have demonstrated a blister prevention superiority of double sock systems vs. single layer socks.
Fitting
Proper fitting of athletic footwear is critical for comfort, injury prevention, and performance. Fitting of shoes, particularly athletic shoes, is a lost art in the modern retail marketplace. The emergence of high-tech sports hosiery products has made the shoe-fitting process even more difficult.
Shoe and foot measurement techniques are archaic in todays modern athletic footwear industry. The Brannock measuring device was developed in 1927, long before athletic shoes were developed and long before high-sports specific hosiery products were invented. The majority of modern-day athletic footwear are manufactured overseas in third world countries where sizing parameters vary significantly even within the same single factory.
In 1995, the author conducted a shoe fit study for a premium sports hosiery company. The results of this study revealed the following:
1) Measuring feet barefoot with a Brannock device successfully predicted accurate athletic shoe size only 30% of the time.
2) When subjects wore a standard cushion-sole sock and were measured, accuracy for shoe size improved 10%.
3) When measuring a subject barefoot (as recommended by the Brannock Company), and then fitting the subject with athletic shoes and thick sports specific socks, the Brannock measurement was accurate only 15% of the time (an 85% failure rate!).
4) When measuring a subject with thick sports specific sock standing on the Brannock device, the accuracy for predicting proper shoe size improved by 10%.
5) When wearing properly fitted shoes with a generic sports sock, adding a thick heavily padded sock demanded an increase in length of shoe 77% of the time.
Therefore, measuring an athlete with a Brannock measuring device has minimal value when correlating with shoe sizes of modern day athletic footwear. Still, the skill of the fitter can allow translation of the shoe size to an "adjusted size" based on a knowledge of inventory and peculiarities of brand-size characteristics. The athlete should be measured and fitted wearing the specific sock that will be ultimately worn with the footwear. This is a reversal of the normal fitting process in most athletic shoe stores where socks are purchased as a "add-on" after shoes have been fitted.
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