How does running shoe design and construction affect injury risk, and how does this affect advice on shoe choices that clinicians give to their injured runners? Andrew Hamilton looks at what the recent research has to say. Running is one of the most popular sports and fitness activities across the globe. However, while it is a... MORE
Snow sport injuries: know the risks, aid prevention
Andrew Hamilton looks at what the most recent research has to say regarding injury risk and prevention for skiers and snowboarders, and the implications for safety.
No sport is free of injury risk, but alpine sports such as skiing and snowboarding carry more risk than most, especially when it comes to more traumatic or life-threatening injuries. With that in mind, it behoves sports clinicians to inform or implement strategies that can minimise injury risk wherever possible.
Snow sports injury is a topic that we first covered in an in-depth Sports Injury Bulletin in 2014 (which you can read here). In it, we demonstrated that data collected worldwide shows skiing and snowboarding are risky pursuits, with 2 to 4 injuries per 1000 participant days – the highest risk being in snowboarders and younger participants(1-6). The fatality rate is also comparatively high, being on a par with cycling and car accidents. In terms of injury types, the data shows that bone fracture is the most common, followed by muscle strain, torn ligaments, joint injuries and dental trauma(7). Surprisingly, concussion is the least common injury; this may be largely thanks to the ubiquitous use of helmets (see figure 1).
Figure 1: Relative risk of the most common skiing and snowboarding injuries(7)
Understandably, much of the previous research into snow sports injury has focussed on acute/traumatic injury. However, over the past five years or so, more recent research has looked at overuse injuries, particularly in skiers. In particular, researchers have identified that skiers are – like other athletes – prone to overuse injuries affecting the lower back, which is the most common overuse injury in skiers, often resulting in chronic lower-back pain (LBP)(8,9). One theory as to the cause of LBP in skiers is their exposure to large amounts of whole body vibrations (WBV), which occur during manoeuvres such as ploughing, short swinging, and carved turns.
Exposure to WBV in connection with various occupations is known to be strongly related to low-back pain(10), which is why international health and safety standards such as ISO 2631 and EU directive 2002/44/EC exist to protect workers from excessive WBV. To investigate this further, an international team of scientists asked a group of former competitive ski racers to perform a number of skiing maneuvers while fitted with body accelerometers (to measure forces/vibration) and a GPS positioning system(11). These manoeuvres were:
- Straight running
- Basic swinging
- Snow plough swinging
- Short swinging
- Carved turns
The data showed that all of the manoeuvres produced significant levels of whole-body vibrations. However, the short swinging and carved turns (see figure 2) produced large amounts so that just 10 minutes of these manoeuvres exceeded the safe recommended WBV level set by European Directive 2002/44/EC. Due to these findings, the researchers concluded that,
“Where active participants train over 100–150 days each year in demanding snow conditions and slopes, there are long-term risks to health. One appropriate preventive measure would be to reduce the number of skiing days and/or the number of runs where high-WBV manoeuvres are required. This is particularly important for younger skiers, since many deteriorations of the spine develop early in adolescence. For recreational skiers who ski relatively infrequently and in lower-load conditions, the risk of WBV injury is low.”
Figure 2: WBV comparison between straight running and carved turns
Upper plot carved; lower plot straight running.
NB: note logarithmic scale – the magnitude of WBV is approximately 100-fold higher during carved turns
Snowboarders are at an even higher risk of acute injury than skiers, and one particularly concerning injury type is spinal injury, which can cause disability and even death in snow-sport accidents. Back protectors can be used to prevent spinal injury but the current testing standards do not evaluate the flexion-extension resistance of these protectors, and to make matters worse, the injury risks due to over flexion have not been studied.
However, in a very recently published study, researchers examined (using a 3-D model) the flexion-extension range of motions of the thoracic-lumbar spine during a typical snowboarding backward fall under varying conditions (eg different speeds, slope gradients, body posture, angle of approach etc)(12). Comparing their data with that from validated vehicle-pedestrian impact data, they found that there was a high risk of spinal injury in most of the 324 accident scenarios. In particular, the thoracic segment T6-T7 had the highest injury risk and incidence, which was exacerbated by higher speeds and larger torso size. The conclusions of this study were that:
a) back protectors should always be worn by snowboarders and that
b) back protectors should protect the vulnerable thoracic vertebrae and be of the correct dimensions to suit the snowboarder’s anthropometry.
Although head injuries in snow sports are not as common as musculoskeletal injuries, when they do occur, the consequences can be severe or even fatal; indeed, brain trauma is the biggest cause of death during snow sports(13). In a detailed analysis of 57 head impact injury videos during 29 alpine, 13 snowboard and 15 freestyle events, most athletes (84%) impacted the snow with the skis or board first, followed by the upper or lower extremities, buttocks/pelvis, back and, finally, the head(13). However, 47% of all falls did involve head impacts and 28% involved two or more head impacts. Of these, 10% of athletes lost their helmets during the fall.
The results above suggest that the use of properly fitting and secured head protection remains absolutely crucial for all snow sport athletes venturing out onto the slopes – something confirmed by another recent study on 549 young skiers and snowboarders participating in snow sports in Colorado(14). It concluded that young athletes who were visiting from out of state were less likely to be wearing a helmet when injured, and importantly, more likely to be severely injured as a consequence; helmeted skiers and snowboarders who were admitted to intensive care had significantly lower injury severity scores than those who were not helmeted.
Equipment and safety
As we have seen above, the use of equipment such as helmets and back protectors should be considered an essential element of any injury-risk reduction strategy. However, recent research has also identified other aspects of equipment that can play a role in injury risk. One study has examined the use of alpine touring boots, which are primarily designed for climbing mountains and snow skiing down on back-country routes(15).
In recent years, there has been a growth in the practice of using alpine touring boots in proper alpine ski bindings (which are really designed for alpine ski boots – not alpine touring boots). With that in mind, the researchers investigated the effect on the retention-release characteristics of alpine touring boots used in proper alpine bindings. The results showed that only around one third of the alpine touring boots released appropriately when used in alpine ski bindings.
The researchers also discovered that changing the visual indicator settings on the bindings (that control the release torque of an alpine system) had little or no effect on the release torque when using alpine touring boots in alpine ski bindings. It was also apparent that while many alpine touring boot/alpine bindings released appropriately in ski shop tests, they did NOT release appropriately in the more complex loading cases that simulated forward and backward falls. The results led the researchers to conclude that the use of alpine touring boots with alpine ski bindings is not recommended as it could increase the likelihood of lower leg injuries.
Bindings and ACL injury
In another study related to binding release, researchers have investigated the link between ACL injury in female skiers and binding release failure(16). To do this, data was collected from 498 recreational skiers who had suffered an ACL injury while skiing (complete rupture or partial rupture), over two thirds of whom were females. The researchers examined the link between injury risk and the following parameters:
- Self-reported skill level and risk taking behaviour
- Ski length
- Date of last binding adjustment
- Perceived speed at the moment of injury
- Type of fall
- Binding release failure of the ski of the injured knee
An analysis of the results showed that binding release failure was reported in 78% of cases of ACL injury, and for female skiers, this rose to 83% (the corresponding rate for male skiers was 66%). Interestingly, the speed of injury at the moment of injury was (perhaps counter-intuitively) inversely related to a binding release failure; a failure was much more likely at lower rather than higher speeds. In terms of the type of fall, the rate of binding release failure was significantly higher during backward falling compared to forward falling (87 vs. 72%).
A breakdown of the results between partial ACL tears and a complete rupture showed that binding release failure was a bigger factor in the latter. Overall, these findings coupled with those above suggest that correctly set up and maintained ski/boot binding systems are absolutely essential when seeking to reduce injury risk. It is beyond the scope of this article to discuss this topic in depth; however, an excellent summary (and video) on the subject can be found here.
As our understanding of injury risk in snow sports continues to increase, more effective strategies to reduce risk can be developed. In this update, we have seen that skiers and snowboarders should pay particular attention to the correct use of head and back protection, while also optimising the boot/ski/board interface. More advanced downhill skiers should also be aware of over overuse injury risk and adjust their training loads and focus on manoeuvres accordingly.
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