Risk of Injury in Skiing and Snowboarding
Abstract & Commentary
Synopsis: By developing a new assessment for injury rates that takes into account distance skied, Ronning and colleagues find that snowboarding is more than three times the injury risk of skiing.
Source: Ronning R, et al. Risk of injury during alpine and telemark skiing and snowboarding. Am J Sports Med 2000; 28(4):506-508.
Ronning and colleagues present a novel way to assess injury risks in skiing, which they term the distance-correlated injury index (DCI). Traditionally, injury rates for alpine skiing have been estimated as injuries/1000 skier days, with skier days estimated on the basis of the number of lift tickets sold. However, Ronning et al argued that estimates based on skier days are erroneous since the hours skied by each lift ticket purchaser are markedly varied (i.e., some skiers ski for less than one hour a day, while others ski from the time the lifts open until they close).
Ronning et al feel that to calculate more accurately the risk of injury, one should assess the number of injuries per 100,000 km skied. Ronning et al’s pilot study addressing the effectiveness of such an injury reporting system was conducted at the Hafjell Alpine Center, the third largest alpine area in Norway (averaging 240,000 guests each season). This mountain is unique from many alpine areas in that skiers ascending the mountain on a lift can only descend on a slope of a defined length. This is in contrast with most ski resorts in which skiers can descend from a lift on one of several runs of varying lengths.
This defined length slope allows Ronning et al to estimate the number of kilometers skied by each skier based on the frequency and location of the lifts ridden by skiers. Ronning et al further subdivide their injury risk factors on the basis of the equipment used (i.e., alpine skis, telemark skis, snowboarding, or "others"), thus establishing the equipment-specific distance-correlated injury index (ESDCI). By this technique, they found the ESDCI alpine was 3.9, the ESDCI snowboard was 13.5 and the ESDCI telemark was 3.0. These data are in contrast with those of others who have reported injury rates in alpine skiing to be similar to those of snowboarding.1,2
Comment by Letha Y. Griffin, MD, PhD
This study emphasizes a frequent limitation of injury data—that is, determining the denominator. The National Collegiate Athletic Association (NCAA) in their Injury Surveillance System reports injury rates as number of injuries per 1000 athletic exposures, defining "athletic exposure" as one athlete playing in one practice or competition. The limitation of this calculation is that, in many sports, all players in any one competition or practice do not play the same amount of time. For example, player A who plays 90 minutes of soccer in a game is assumed to have the same injury exposure as player B who plays only five minutes of the game.
Similarly, Ronning et al thought it inappropriate to use skier days as the denominator for their injury rate analysis, opting instead to use distance covered by the skier or snowboarder. While their argument is logical, the ability to adopt their scheme as a standard would necessitate developing a system to record distances traversed by skiers and snowboarders. In most ski areas, lifts lead to runs of variable distances and, therefore, distance cannot be estimated from the lift ridden by the skier as was done in this study.
A major limitation of Ronning et al’s study and hence their comparison of injury rates in alpine skiing and snowboarding is the manner in which they differentiated the number of skiers and snowboarders. Their numbers were obtained by extrapolating counts of those "using the lifts in a pre-designated random fashion in periods of twenty-minutes, observing each lift thirteen times." Registering the primary equipment to be used by each individual (skis or boards) at the time of lift purchase may result in a more accurate numerator for the authors’ study, although admittedly the lift purchaser might elect to change equipment during the course of the day, skewing the data somewhat. Despite this limitation, Ronning et al’s method for injury calculation in skiing and snowboarding is an intriguing one and merits further consideration.
References
1. Bladin C, McCrory P. Snowboarding injuries. An overview. Sports Med 1995;19:358-364.
2. Pino EC, Colville MR. Snowboard Injuries. Am J Sports Med 1989;17:778-781.
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