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Ergonomic considerations for sports clothing

This is an excerpt from Ergonomics in Sport and Physical Activity by Thomas Reilly, PhD, DSc, FErgS, FIBiol.


Clothing ensembles in occupational settings are subject to material standards. The influence of clothing is affected by various factors that include insulation for protection against cold and heat, vapor permeability or capacity for heat loss, air permeability, vapor resistance, and protection from penetration of pollutants. Liquid protection against chemicals and waterproofing for repellence of water and rain are also important properties, as is fire protection for motor racing drivers. The visibility of the garments and their mechanical properties are also relevant. In outdoor conditions the solar absorptivity of clothing is relevant, although this factor is not included in indices such as WBGT (wet bulb and globe temperature) in measuring environmental heat stress.

The appropriateness of the clothing worn for sport participation has been a neglected aspect of its design, because fashion, facilities, and market forces have outweighed ergonomics criteria. The use of size indicators in clothing accommodates inherent differences in participants, but there are often quite radical differences between sports. Loose-fitting clothing is often used in hot climates to keep the microclimate next to the skin cool. The dynamic air exchange, or pumping effect, keeps the area beneath the clothing cool by means of convection and evaporation. Exposure of the skin surface for evaporative cooling may be important for endurance running. Tightly fitting clothing is preferable for enhancing aerodynamic properties of the body in cycling, sprinting, and downhill skiing, for example.

Design of clothing for sprinters has used information from wind-tunnel tests to reduce drag, with the anticipation of improved performance. A whole-body garment was used by Cathy Freeman when winning the Olympic 400 m gold medal at the Sydney Olympics in 2004, although the added value of the latter in terms of energetics is considered marginal. Similar principles have been incorporated into clothing worn by swimmers and ski jumpers. For this latter group, attention has been given to the appropriateness of the traditional ski-jumping boots when extraordinarily high power output must be generated by the jumper at takeoff (Virmavirta and Komi, 2001).

The design of swim clothing has progressed from traditional trunks for male competitors and single (one-piece) suits for females. Mollendorf and colleagues (2004) examined swimsuits varying in body coverage from shoulder to ankle, waist to ankle, and briefs. They measured passive drag at different towing speeds during starts and push-offs in a swimming pool. They concluded that it is possible for body suits that cover the torso and legs to reduce drag and improve performance of swimmers. In a later study, Chatard and colleagues (2008) demonstrated that swim performance over six distances from 25 to 800 m was improved by 3.2% on average when normal swimwear was replaced by a full-body or waist-to-ankle fastskin suit. The gain was greatest with the full-body suit, attributed to a reduction in passive drag, lower energy cost, and a greater distance per stroke. Individuals without access to the new designs of whole-body suits for training might be at a disadvantage in competition. These types of swimsuit formed the majority of those worn at the 2008 Beijing Olympics even though a sizeable proportion of competitors used the more traditional designs. Nevertheless, the advantage of swimsuit technology to reduce hydrodynamic drag has been emphasized by more than a hundred world records achieved by competitors in swimming in the first 12 months of its introduction. Obvious disadvantages are the costs of the suit and the time taken, about 15 minutes, to don it. Six months after the Beijing Olympics, the international governing body FINA clarified the rules about design of swimsuits, specifying that swimsuits must not cover the neck or extend past the shoulders and ankles. The Federation reaffirmed its intention to continue monitoring the evolution of sport equipment with the main objective of keeping the integrity of the sport.

Special clothing may be needed to combat the specific hazards presented in some sports. Motor racing suits may need to offer cooling as well as fireproofing because of the heat stress and risk of fire involved. Many machine sports also require pit staff and drivers to wear ear protectors because of the high noise levels experienced. Wet suits for aquatic sports enable users to tolerate sustained periods of immersion in cold waters. Development of novel fibers has improved protection against wet and cold conditions outdoors while permitting sweat to flow through the garment (Holmer and Elnas, 1981).

Survival time in ocean temperatures not quite ice-cold is increased by wearing dry suits or wet suits. Dry suits are designed to keep the body dry, whereas wet suits allow a minimal amount of water through the material; the water is then heated by the body and, after equalizing with skin temperature and forming part of the boundary layer adjacent to the skin, prevents further loss of heat from the skin surface. Wet suits are usually made of closed-cell neoprene to a thickness of 3 to 6 mm and a close fit is needed for effectiveness. Suits that cover the arms are most effective because more heat is lost from the arms compared to the legs when each limb is exercised at the same oxygen uptake. The time of useful consciousness in water temperatures of 5oC can be extended threefold compared to wearing normal clothing by the use of a neoprene wet suit 5 mm thick but the time is increased by a further 100% if a dry suit is worn with dry underclothing (Reilly and Waterhouse, 2005).

The study of protective garments in a variety of extremes in sports and industrial contexts, such as on the mountains or deserts or in accidental immersion in water, is still a rich vein of ergonomics research. There is a growing demand for merino wool garments, normally used by mountaineering and skiing groups, as a wicking layer. It promotes evaporation of sweat, enhances thermal comfort, and does not smell afterward-a marketing claim for après ski contexts. Comparatively little attention is given to the added value of gloves and headgear in extreme conditions where choice is largely based on subjective evaluation of prevailing environmental conditions.

Sports brassieres have replaced the conventional fashion bra for females competing in track-and-field athletics, road running, and games such as football, squash, and tennis. The original "jog-bra" was designed to reduce movements of the female breast during locomotion and decrease pain and discomfort. Such problems included "jogger’s nipple," an irritation also experienced by male runners attributable to chafing from their clothing. A stretchable absorbent fabric such as Lycra is commonly used in sports brassieres. The products are made either with encapsulation molded cups or compression designs that limit motion by flattening the breasts. Their features are incorporated into the running tops worn by some distance runners and triathletes without an accompanying shirt. A concern addressed by Bowles and colleagues (2005) was that sports bras were too tight and restricted breathing. The investigators observed no effect on respiratory function for subjects who wore a sports brassiere, which was superior to a fashion bra and a no-bra condition. The investigators recommended that active females wear a sports brassiere to reduce breast movement and related breast pain. In view of individual differences in size, a proper fit is important. Encapsulated bras are more suitable for large-breasted joggers, whereas compression bras are preferable for the majority of runners. The superiority of the compression bras was demonstrated by White and colleagues (2009) who reported the least discomfort with the compression design. Both sports bras were more comfortable than an everyday bra, while wearing no bra was the most uncomfortable condition. In their kinetic evaluations, White and colleagues demonstrated the importance of curtailing mediolateral, as well as vertical, displacement of the breasts to provide female runners with sufficient support for their performance and comfort during their runs.

Compression garments have been promoted for use in sport as well as other contexts. Compression stockings are commonly used by airline travelers to reduce the risk of incurring deep-vein thrombosis. In sport, compression clothing has been designed to improve recovery following exercise and training. Although this fashion has gained acceptance among professional athletes, the physiological mechanisms for any positive benefit are not clearly established. A similar concept applies to the tight-fitting shirts worn by a number of the teams in the finals of the 2007 World Cup for Rugby Union, with claims of increasing energy levels through transfer of ions to the body. It is unlikely that such interventions determine team success at this level of competition.

 




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