The debate continues surrounding appropriate timing and volume for implementing plyometric training in return-to-play rehabilitation. Pat Gillham looks at the latest thinking ‘Plyometric exercise’ was a term coined in 1964(1). Plyometrics exercises exploit the benefits of the plyometric regime and involve the Stretch-Shortening Cycle (SSC)(2). Thanks to the muscles’ pre-stimulation during the eccentric phase, plyometrics... MORE
Snow sports: time to think about injury prevention
Andrew Hamilton looks at what the scientific research has to say regarding snow sports injury and injury prevention.
Skiing and (increasingly) snowboarding are becoming mass-participation sports, enjoyed by participants of all ages and abilities. For example, in North America alone, there are more than 78 million annual visits to ski areas by skiers and snowboarders of all ages(1). Moreover, the popularity of family holidays means that snow sports are not just enjoyed by adults, but by younger participants too. Studies have shown that 20% to 30% of snow sport participants are children and adolescents, while an estimated 15% of Canadians over the age of 12, and 4% of the US population over the age of seven, reported participating in alpine skiing, cross-country skiing or snowboarding at least once in 2008-2009(2).
However, with increasing snow sport participation comes an increased rate of traumatic injury and the data points to a significant risk. Figures from US ski resorts showed that in 2002, an estimated 77,300 skiing and 62,000 snowboarding injuries were treated in US emergency departments alone, including 10,700 traumatic brain injuries(3). Another study found that snowboarding is responsible for an estimated 25% of nonfatal outdoor injuries requiring emergency care(4).
Studies conducted in a number of countries across Europe and North America have indicated that the risk of injury for skiers and snowboarders is approximately 2 to 4 injuries per 1000 participant days, with the highest risk in snowboarders(5-9). Children and teenagers in the 7-17 years age bracket appear to have higher rates of injury than younger and older participants(2). Injuries requiring referral to a tertiary trauma centre have been estimated at 0.06 to 0.07 per 1000 participant days(10).
How risky is skiing?
Most serious skiing accidents involve high-speed collisions with stationary objects such as trees and lift poles. In such collisions, the incidence of head injury is high, increasing the risk of fatality. Studies on this risk shows that the skiing deaths are estimated to occur at a rate of 0.5 to 1.9 per 1 million participant days(11,12). In the 2009/10 season, there were 38 deaths in the US with a rate of 0.64 deaths per million visits(13). To put this into perspective however, the risk of a skiing fatality is not significantly higher than some other common human activities; the risk of death is roughly around the same order of magnitude as death in car accidents or cycling – about 0.1 deaths per million hours of exposure(14). Moreover (as we shall see later) there are ways of reducing this risk.
There is recent evidence that the incidence of traumatic brain injury and spinal cord injury in skiing and snowboarding is increasing worldwide. This increase in serious injuries may be related to increased risk-taking, such as jumping and acrobatic activities, both on new terrain and in snow resorts/parks specifically designed for snowboarding(15).
Typical injuries sustained in snow sports
A number of reviews have been published that summarise the epidemiology of skiing and snowboarding injuries. Skiers tend to sustain injuries to the lower extremities; snowboarders on the other hand are much more likely to sustain injury to the upper extremities (see figure 1)(16-17). Knee injuries are the most common type of injury in skiing and constitute up to 36% of all ski injuries, according to the literature(18). Snowboarders sustain more torn ligaments and sprains/strains, caused by a) standing sideways on the board and b) the absence of a security binding which opens on its own in case of a fall. In a snowboard fall, the wrists are especially vulnerable to injury, especially on impact.
Figure 1: Injury breakdown in skiers and snowboarders(19)
Black = skiing; dark grey = snowboarding; light grey = combined skiing + snowboarding
In a Canadian review study published in 2012, researchers investigated the epidemiology of snow sport injuries in younger persons and children(20). It reported that in alpine skiing, the most common injury site is the lower extremity (40% to 60% of all injuries); knee injuries (egfractures and sprains) are common and observed more frequently in younger children. Other typical injuries are to the head and neck (10% to 20%), upper extremity (15% to 25%), and thumb (10% to 20%). In snowboarding, the most commonly injured site injured is the wrist (22%), with upper-extremity injuries (including wrist injuries) in approximately 50% of cases. In this age group, head injuries are more common in snowboarders than skiers. Of these, 10% required emergency treatment and 30% to 40% requiring subsequent admission for trauma treatment.
Another study examined the epidemiology of snow sport injuries occurring at Cairngorm, Glenshee, and Nevis Range ski areas in Scotland during the 1999–2000 winter season(7). Personal details, snow sports related variables, diagnosis, and treatment were recorded, and control data were collected at random from uninjured people at all three areas. A total of 732 injuries were recorded in 674 people and the injury rate for the study was 3.7 injuries per 1000 skier days – very much in line with the studies above(5,6,8). Once again, snowboarders sustained more injuries to the upper limb and axial areas than their skiing counterparts, and skiboarders and snowboarders also suffered a higher incidence of fracture (see table 1).
Table 1 Anatomical location of injury by equipment published 2002 (7)
|Alpine ski n (%)||Snowboard n (%)||Skiboard n (%)|
|Shoulder||33 (6.9)||19 (8.9)||1 (3.2)|
|Humerus||5 (1)||19 (8.9)||1 (3.2)|
|Elbow||7 (1.5)||11 (5.2)|
|Wrist||15 (3.1)||47 (22.1)||2 (6.5)|
|Thumb||34 (7.1)||8 (3.8)||1 (3.2)|
|Hand/digit||22 (4.6)||8 (3.8)|
|Lower limb||255 (53.1)||46 (21.6)||23 (74.2)|
|Knee||176 (36.7)||26 (12.2)||15 (48.4)|
|Ankle/calf||39 (8.1)||15 (7)||5 (16.1)|
|Foot||1 (02)||4 (1.9)|
|Axial||109 (22.7)||69 (32.4)||4 (12.9)|
|Head/face||68 (14.2)||42 (19.7)||1 (3.2)|
|Chest||9 (1.9)||7 (3.3)||1 (3.2)|
|Neck||7 (1.5)||5 (2.4)|
|Back||14 (2.9)||7 (3.3)||2 (6.5)|
|Pelvis||5 (1)||3 (1.4)|
|Abdomen||6 (1.3)||2 (0.9)|
|Total||480 (100)||213 (100)||31 (100)|
Injury trends over time
Much of the data on snow sports injury was collected in the late 90’s and early 2000s – coinciding with a time of rapidly growing popularity. But have the injury trends changed over time and what are the implications for injury prevention? A US study in 2012 looked at snowboarding injury trends at a ski resort in Vermont over a period of 18 seasons (1988-2006) and compared these with alpine skiing injuries over the same period(21). The researchers also looked at the differences in injury patterns between snowboarders and alpine skiers as affected by age, experience, and sex.
The injury rates were assessed as mean days between injuries (MDBI – the lower the number, the higher the injury rate). The findings were as follows:
- The average MDBI for all injuries among snowboarders was 345 as compared with 400 for skiers. The most common type of injury for snowboarders was a wrist injury (MDBI, 1258), while for skiers, it was an anterior cruciate ligament (ACL) sprain (MDBI, 2332).
- Wrist injuries accounted for 27.6% of all snowboard injuries and 2.8% of skiing injuries.
- ACL injuries composed 1.7% of all snowboard injuries and 17.2% of skiing injuries.
- Among snowboarders, more wrist injuries, shoulder soft tissue injuries, ankle injuries, concussions, and clavicle fractures were seen, while skiers had more ACL sprains, medial collateral ligament (MCL) sprains of the knee, lateral collateral ligament (LCL) sprains of the knee, lower extremity contusions, and tibia fractures.
- There was a trend towards an increased incidence of clavicle fractures and a decrease in MCL injuries and ankle injuries among snowboarders over time.
- Skiers had a decrease in thumb metacarpophalangeal-ulnar collateral ligament (MCP-UCL) injuries and MCL injuries of the knee over time.
- The highest rate of injury was among young, inexperienced, female snowboarders.
Overall, while injury rates in snowboarders have fluctuated over time, they currently remain higher than in skiers. This may be partly due to changing demographics – snowboarding is often portrayed as a youthful, ‘cool’ sport and the data shows that injured snowboarders were significantly younger, less experienced, and more likely to be female than injured skiers or snowboard control participants. The rise in rates of clavicle fracture may be linked to an increased interest in snowboarding acrobatic/airborne manoeuvres.
Injury prevention in snowsports
Snowboarding equipment– Since its inception, snowboarding has consistently been associated with a higher incidence of upper limb injuries than alpine skiing, with the wrist being the single commonest site of injury. In the event of a fall, the natural tendency for a snowboarder is to stretch out (and land on) the hand. Back in 1999, the evidence suggested that less than 10% of snowboarders were using wrist guards to protect the wrist in such falls, despite there being some epidemiological and laboratory evidence to support their use(22-24). With an increasing emphasis on safety, you might think that the situation today is radically different but the evidence is less encouraging.
A 2011 meta-study by US researchers surveyed all the published literature on wrist guard use, injury prevention, the biomechanical effects of wrist guards, and the various types of wrist guards commercially available for snowboarders(25). The authors concluded that the use of protective equipment for the wrist is a useful method for the prevention of injury. However, they pointed out that while numerous studies looked at the effect of wrist guards, there was no consensus on which particular type of wrist guard would be most effective; the majority of the studies did not mention a brand name or a description of the type of wrist guard that was used by participants. It was also apparent that the literature typically reported low usage of wrist guards by snowboarders – as low as 6% – possibly due to aesthetics, social acceptance, fit or wrist guard and availability.
Some research has suggested that using wrist guards may increase the risk of sustaining an elbow, upper arm or shoulder injury – by transferring the loading during a fall further up the arm. However, the evidence for this is conflicting and has not been confirmed in a controlled trial or well-designed prospective study and the current best advice for snowboarders is to use a wrist guard to help prevent injury.
Skiing equipment– Injury incidence among skiers has declined over several decades, largely due to improvements in ski equipment, particularly boots and bindings; evidence shows that modern bindings reduce the incidence of foot, ankle and lower tibial injuries providing they are properly mounted, adjusted and maintained(26,27). Many injuries are the result of poorly adjusted bindings; in one study of adult lower extremity equipment related injuries it was determined that in 96% of cases the ski bindings did not release when the injury occurred(28). Non-release of bindings has also been reported as an injury contributor in other studies of both youths and adults. In one study, skiers younger than 13 years of age with poorly adjusted bindings were more likely to be injured than children with properly adjusted bindings(29). Unsurprisingly therefore, some researchers have proposed that a professional should adjust children’s and beginner’s ski bindings at the start of each lesson and that these groups should be taught to check their bindings at the beginning of each ski day(30).
Snowboarding and skiing equipment– One area where there’s little doubt over effective equipment-based injury prevention is helmet use. A recent systematic review found that helmets significantly reduce the risk of head injury(31). Skiers and snowboarders wearing a helmet were less likely to have a head injury, and this risk was further reduced when studies that included children younger than 13 years of age were included. Overall, the pooled results showed that helmet use reduces the risk of head injury by around 35%.
Some researchers have raised concerns that while helmet use during skiing and snowboarding reduces head injury rates, it might increase the risk of cervical spine injuries. However, these concerns are not supported by a number of case control studies(32-35)and a 2010 systematic review also concluded that helmets were not associated with an increased risk of neck injury(31). Moreover, there is also no evidence that helmet use in skiing and snowboarding is associated with riskier behaviour(36,37). The clear conclusion here is that helmet use should be considered mandatory at all times where safety is a concern.
Physical conditioning for snowsports and injury prevention
Strength, endurance and cardiovascular fitness are central components in sports injury prevention across a wide range of sports, and yet in snowsports, there seems to be a much greater emphasis on equipment-based and third party solutions. A comprehensive and systematic review of the literature published early this year looked at injury prevention recommendations specific to recreational alpine skiers and snowboarders. The focus was to discern recommendations that targeted physical fitness, exercise and/or training in the prevention of musculoskeletal injuries in these two sports(38). Studies were included if they addressed injury prevention, recreational alpine skiing or snowboarding and musculoskeletal injuries and articles on elite athletes were excluded.
Overall, 80 recommendations for the prevention of musculoskeletal injuries in recreational alpine skiers and snowboarders were identified and classified into five main groups:
- Equipment use (n = 24)
- Education and knowledge (n = 11)
- Awareness and behaviour
- Experience (n = 10)
- Third-party involvement (n = 20)
Amazingly, there were no studies that made recommendations pertaining to physical fitness, exercise and/or training per se, or its role in preventing injury! The authors commented thus on the frequent recommendations for preventing skiing and snowboarding injuries by an equipment-based or third party approach: “The dominance of equipment-related measures in the injury prevention literature may be rationalised from a sports biomechanics viewpoint, as these activities involve high velocities and impact forces. Nonetheless, this also indicates a need for appropriate levels of strength, endurance and conditioning to meet the technical demands of these sports.”In other words, while it makes sense to take precautionary measures regarding appropriate equipment use, awareness, behaviour etc, neglecting essential physical conditioning could be counterproductive. Unfortunately, there are no peer-reviewed studies on which type of conditioning program is most appropriate for snowsport injury prevention, but here are some of the general principles that are likely to be useful :
- Strength– Higher levels of muscular strength can improve a skier’s/snowboarder’s ability to relax and still maintain control, while making quick adjustments needed on uneven terrain. All the major muscle groups of the body (especially the core and legs) are used in these sports and should be included in a strength training programme.
- Flexibility– Flexibility training skiers and snowboarders should focus on the lower extremities although snowboarders need to stretch the upper body as well.
- Endurance– Like strength, higher levels of endurance allows the skier/snowboarder to relax and focus more easily on the technical demands. Good dry-land cardiovascular endurance training includes road, mountain or stationary biking, which builds stamina and focuses on the leg muscles used during skiing and snowboarding.
As well as flexibility and endurance training, some balance and agility training may also be beneficial. In addition, an ACL injury prevention program may be particularly helpful. Although originally designed for football players, the principles and concepts are also applicable to skiers and snowboarders. A good ACL injury-prevention program incorporates neuromuscular training/control, muscle strengthening, plyometrics, as well as education and feedback regarding body mechanics and proper landing patterns in a dynamic atmosphere(39). Programs that begin at least 6 weeks prior to the start of snowsport activity are likely to be more effective. Training sessions should last around 15–20 minutes and be performed at least three times a week.
Skiing and snowboarding by their very nature carry a significant risk of injury, which can sometimes be serious. The most common injuries are to the knees in skiers and wrists in snowboarders, and the rate of injury is highest in beginners, the less experienced and the young. The correct use of equipment (eg bindings when skiing and wrist guards when snowboarding) is critical for reducing injury risk. Helmet use is also vital to reduce the incidence and severity of head injury in both skiers and snowboarders. In addition to equipment-based measures, an appropriate pre-skiing/snowboarding conditioning programme may also play an important role in ensuring a trip to the slopes is memorable for all the right reasons!
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