NOT BE TRIVIALISED, AND THE MOST EFFECTIVE WAYS TO REDUCE HEAD INJURIES AMONG PLAYERS IS BY &#x201C;PURPOSEFUL HEADING&#x201D; OF THE BALL AND A TOTAL COMMITMENT TO &#x201C;FAIR PLAY&#x201D;
fatigue may influence the risk of injury. Giza et al. (7) reported injury data from the first two seasons of the Women&#x2019;s United Soccer Association (WUSA) relating to incidence, anatomic location and position. They recorded the position of each player at the time of injury in 168 players. Midfielders sustained the most injuries (57, 34.1%) followed by defenders (47, 28.1%), strikers (38, 22.8%), and goalkeepers (26, 15.0%). Midfielders suffered significantly more injuries than all other players (P<0.007) but this number of injuries was not statistically significantly different than those in other field players (7).
Environmental risk factors Environmental factors are all extrinsic factors and include use of knee bracing, the choice of footwear, the playing surface and field conditions, and the weather (climate).
Prophylactic and functional knee bracing No studies have shown conclusively the effectiveness of functional knee braces in prevention of injuries. Deppen et al. (22) examined the use of prophylactic knee bracing in eight American high-school football teams over a 4-year period. Of 21,640 exposures in the braced group there were 23 knee injuries; this compares with 26 knee injuries in 19,484 exposures in the non-braced group. These differences were not statistically significant, and the same applied to the severity of injuries in the two groups, so combining these findings with the costs of bracing, the use of prophylactic bracing is not recommended.
Footwear In 1974, Torg et al. (23) used a &#x201C;release coefficient&#x201D; to quantify the force-to-weight ratio of shoe&#x2013;surface interactions &#x2013; a way of looking at their friction. Their work was reinforced by Heidt et al. (24) who tested 15 different types of athletic shoes and found that 73% were &#x201C;unsafe&#x201D; or &#x201C;probably unsafe&#x201D; due to excessive friction. When designing shoes, a high friction coefficient may enhance performance, but it may cause ligamentous injuries. Ekstrand et al. (25) suggest an optimal range in shoe design, that will minimise rotational friction, thus avoiding injury, and optimise transitional friction with a surface to enhance performance when cutting or decelerating (25).
Playing surface As well as footwear, the type of playing surface must be considered. These factors may increase the rate of non- contact anterior cruciate ligament (ACL) injuries in women, relative to the incidence in men. One study among male and female European team handball players (26) found
CONCUSSIONS IN FOOTBALL ARE A SERIOUS ISSUE THAT SHOULD
that wooden floors (parquet; generally with low friction) were associated with fewer ACL injuries than artificial floors (generally with high friction). A total of 174 ACL injuries were recorded over 11 seasons on wooden or artificial floors. Nine injuries (out of 174) occurred in men (0.24 injuries per 1000 AEs <+/&#x2013;> 0.09) and 44 in women (0.77 <+/&#x2013;> 0.04). Among the men&#x2019;s injuries, four were incurred on wooden floors (0.32 <+/&#x2013;> 0.13) and five on artificial floors (0.20 <+/&#x2013;> 0.12). Among the women&#x2019;s injuries, eight were on wooden floors (0.41 <+/&#x2013;> 0.09) and 36 on artificial floors (0.96 <+/&#x2013;> 0.04). The risk of ACL injury appears to be higher for women than men on both artificial floors and wooden floors (26). Uneven playing surfaces may also play a role in ACL
incidence. In the study by Huston et al. (27), injured athletes reported landing or stepping onto an uneven surface such as grass with inconstant levels, or another player (27). Irrigation of the playing field may also have an effect. Scranton et al. (28) identified 61 non-contact ACL injuries among 22 National Football League teams over the course of four seasons. They looked at variables such as the type of surface and shoe and playing conditions. They also looked at shoe spatting, in which tape is wrapped around the circumference of the shoe in the midfoot region. There were 40 injuries in athletes wearing conventional cleated shoes on natural grass compared with 21 on an artificial surface. Injuries during game-play exceeded those during practice (47.5% of overall injuries even though they spent five times longer practising than playing. Of these game-related injuries, 95.2% occurred on a dry field. Ekstrand et al. (25) prospectively compared the incidence
of injury for five female and fifteen male elite football teams competing on either third-generation artificial turf and natural grass. They was no significant difference in overuse injuries on artificial turf and grass for either men or women. The incidence of acute injuries did not differ significantly between artificial turf and grass for men either when they were playing games (22.4 vs 21.7; RR 1.0; 95% CI 0.9&#x2013;1.2) or training (3.5 vs 3.5; RR 1.0; CI 0.8&#x2013;1.2). This was similar to the findings in women: there were no significant difference in acute injury rates related to playing surface when they were playing games (14.9 vs 12.5; RR 1.2; CI 0.8&#x2013;1.8) or training (2.9 vs 2.8; RR 1.0; CI 0.6&#x2013;1.7). These recent findings may signify an improvement in the design of artificially turfed surfaces that might be more like natural grass than earlier generations.
Weather and climate Orchard et al. (29) analysed 5910 National Football League team games to determine any correlation between knee and ankle sprains, playing surface, and weather conditions. They found fewer significant ankle sprains in games in natural grass stadiums compared with indoor (AstroTurf&#x2122;) domes. They also found fewer significant knee sprains in grass stadiums than indoor domes, and this was directly related to the cold and wet outdoor weather on grass surfaces. The same was true for outdoor AstroTurf&#x2122; stadiums, whereby cold weather was associated with fewer ACL injuries than warmer weather. The incidence of ACL was lower in the later (cooler) months of the season in open stadiums &#x2013; both on AstroTurf&#x2122; and natural grass) but not in domes. The researchers suggested that cold weather is associated with fewer knee and ankle injuries in outdoor stadiums (both natural grass and AstroTurf) because of lower friction between shoes and the surface (29).
sportEX medicine 2011;47(Jan):14-21
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