With regard to the risk factor ‘adverse crash behavior’, awareness training of how injuries occur (e.g. by explaining typical injury mechanisms) and how these can be avoided has been demonstrated to reduce serious knee sprains by up to 62 % in trained patrollers and instructors [
57]. Even if these kinds of interventions might be more challenging to implement when working with competitive athletes, they could be effective for some injury situations (e.g. when the ski abruptly catches the snow surface while the skier is trying to get up after slipping out sideways; in this case, teaching athletes not to get up while they are in motion might help to prevent the occurrence of typical ACL injury mechanisms).
With regard to ‘low peripheral body temperature’, the International Olympic Committee (IOC) and the FIS follow the strategy of avoiding competitions when the effective windchill temperatures are colder than −27 °C [
36]. Expert stakeholders have suggested the compulsory use of thicker racing suits with enhanced thermal insulation [
35] since clothing represents the most important modifiable factor influencing injury risk when being exposed to cold temperatures [
37].
With regard to the risk factor ‘pre-injury’, meaningful screening methods identifying athletes at high risk of (re)injury [
58‐
60] might help to develop sophisticated and individualized prevention and/or return-to-sport training programs [
61], and are therefore essential tools for controlling the risk of (re)injury and safely returning to sport. Guided by the current body of knowledge on non-contact ACL injury mechanisms in team sports [
62], Hewett et al. [
58] introduced a biomechanical screening method that assessed neuromuscular control and valgus loading during jump landings aimed at predicting the risk of prospective ACL injuries. In fact, athletes who later sustained an ACL injury showed higher knee valgus angles at the initial screening than those who remained uninjured. Since typical ACL injury mechanisms in alpine ski racing include similar loading patterns to those identified in team sports [
27], the proposed jump-landing screening test might also be effective for predicting the risk of ACL injuries in competitive alpine skiers. However, as ACL injuries in alpine ski racing mostly occur in situations with an asymmetric loading distribution between the outside and inside leg (i.e. while turning) [
25], and since there is only moderate correlation between knee valgus angles in drop jumps and sidestep cutting maneuvers [
63], sidestep cutting-based methods might be more meaningful screening tools.
Another screening method widely discussed in the context of injury prevention in alpine ski racing is the hamstrings to quadriceps (H/Q) ratio [
64,
65]. The basic idea behind this approach is that strong hamstring muscles could prevent the anterior shift of the tibia relative to the femur during typical mechanisms, leading to ACL injuries. Despite several attempts, a significant effect of optimized H/Q ratio on the ACL injury risk of competitive alpine skiers has not been demonstrated. The only difference between ACL-injured and non-injured athletes reported in literature was related to the knee joint angles at which peak hamstring torques were developed (i.e. at deeper flexion angles in non-injured athletes) [
65]. A major drawback of reporting peak-to-peak H/Q ratio (i.e. the most commonly used screening approach) is that this ratio provides little information about the interaction between the two muscles in the range of motion in which ACL injuries typically occur (i.e. in deep flexion) [
65]. Moreover, considering the very short period of time during which ACL injuries occur (<60 ms) [
28], it is not only a question of the strength of the hamstrings and quadriceps but also a question of how rapidly these muscles can be coactivated. In view of these aspects, an alternative ‘rapid H/Q strength’ screening protocol introduced recently [
59] might open new possibilities for detecting strength deficits in ACL-reconstructed athletes and the prevention of ACL injuries in general. The protocol explicitly suggests the assessment of rapid H/Q strength at joint flexion angles meaningful for alpine ski-racing injuries (70°) [
59]. In addition to this alternative screening protocol, a systematic evaluation of functional lower limb asymmetry by means of phase-specific kinetic impulse during countermovement and squat jump tasks might help to better monitor the progress in rehabilitation following ACL reconstruction, and to establish objective standards for a safe return to sport [
60].
With regard to ‘fatigue within a course or a training session’, an active on-hill recovery has been demonstrated to optimize blood lactate clearance and to increase run completion rates [
66]. In this context, a superior physical fitness level might also be a reasonable prevention measure [
25,
34,
35]. With respect to specific physical fitness factors, a recent study provided evidence suggesting that training of ‘core strength’ and avoidance of ‘core strength imbalances’ are key measures for the prevention of ACL injuries in alpine ski racing [
24].
To avoid ‘technical mistakes’ while skiing, sport-specific balance or neuromuscular training might be effective prevention measures [
27,
67] since wearing ski boots is known to additionally challenge the dynamic task of maintaining balance [
67]. Recent studies have shown the ability of neuromuscular training programs to reduce the risk of ACL injuries in sports other than alpine ski racing [
68‐
70].
With respect to the ‘ski-plate-binding-boot’ system, several prevention measures have been previously promoted in the literature. First, ‘reduced standing height’ is expected to reduce knee joint loading, particularly during turns with large amounts of skidding [
34,
35,
43]. Moreover, reduced standing height is assumed to reduce the risk of adversely catching the ski edge [
43], which is known to play a central role in the causation of ACL injuries in alpine ski racing [
27]. In the downhill competition discipline, additional preventative gain of lower standing height might be found in reduced kinetic energy; however, this might only be the case if this reduction is combined with other ski geometry-related prevention measures [
71].
Second, ‘skis with reduced torsional stiffness’ are perceived to be easier to get off the edge once the ski is carving and corrections are required [
34]. Consequently, altering the skis’ stiffness has been suggested to increase the athletes’ safety [
35]. From a theoretical perspective, it is plausible that a ski that is less stiff in torsion will less aggressively engage the snow when being edged, and will be easier to pivot or make slip, if necessary [
46]. In fact, a model-based parameter study found that reduced (torsional) ski stiffness resulted in more pronounced skidding the more speed increased within a sequence of ski turns [
72].
Third, less-stiff boots might help protect athletes from injury because they are less direct in force transmission and are therefore less aggressive at ski–snow interaction [
34,
35], two crucial factors in the causation of skiing-related ACL injuries [
28]. However, this might also compromise the athletes’ performance, and it appears to be difficult to simultaneously address both safety and performance interests. With regard to the design of ski boots, two promising approaches have been introduced. One approach is a ski boot that allows the rear spoiler to be released when posterior-directed force is applied [
73]. Another approach to prevent the knee from adverse loading patterns might be found in optimized boot setups that avoid valgus misalignments [
74]. For a more detailed overview of recent advances in the design and production of ski boots, the reader is referred to a recent review by Colonna et al. [
75].
Fourth, it has been suggested that less-shaped and longer skis with a reduced profile width protect the health of athletes, particularly when these characteristics are combined [
6,
28,
34,
35,
51,
71,
76‐
78]. Less-shaped skis (i.e. skis with greater sidecut radii) were found to be associated with a reduced self-steering effect (i.e. the ski turns by itself if it is edged and loaded) and less aggressive ski–snow interaction [
51,
76]. These two factors are known to play a central role for the causation of ACL injuries in alpine ski racing [
28]. Furthermore, less-shaped skis were found to be associated with reduced kinetic energy and lower ground reaction forces during the turn phases in which most of the injuries are known to occur [
76,
77,
79]. This is in line with theoretical expectations [
44,
80]. Longer skis are perceived to be safer due to increased comfort and enhanced predictability at high speeds [
34,
35]. Skis with reduced profile width are expected to be less difficult for the skier to get off the edge once they are carving and corrections are needed [
34]. Moreover, skis with reduced profile widths are less likely to cause the knee joint to move unfavorably close to the range of motion end positions in transversal and frontal planes, potentially decreasing the risk of degenerative knee injuries [
81].
With regard to gates, the development of alternative panels/poles with less resistance or an optimized release mechanism when hooking in has been suggested by WC expert stakeholders [
35]. Although such systems have become standard at FIS WC races in recent years, there is still potential for further advancements [
25].
A strategy with great potential for reducing the risk of injury would be the avoidance of non-releases or inadvertent releases of bindings. However, based on what is known to date, it will be a very challenging task to design a binding system that can differentiate between adverse internal rotation and valgus loading in injury situations, and the loading patterns in normal (non-injury) skiing situations in alpine ski racing [
27]. Moreover, today’s release bindings are not able to sufficiently protect the knee since their degrees of freedom are limited and only sense those forces that are translated at the boot–ski interface (i.e. forces near the ankle) [
65]. Obviously, sensing additional information (e.g. a combination of upright/lateral forces at the toe and heel, strain on the back of the ski boot or injury-relevant body positions) would be needed to allow more ‘educated decisions’ as to whether the binding should release [
65]. In this context, current research efforts mainly focused on the development of mechatronic bindings [
82]. Another approach might be found in an innovative binding plate with load-limiting features [
83]. For a more detailed overview of the current technical possibilities, the reader is referred to a recent review by Senner et al. [
82].
In order to protect the athlete’s body from injury, different protective devices have been proposed in recent years, i.e. hand/arm protectors, back protectors, knee and lower-leg protectors, knee orthoses, and airbag systems [
84,
85]. Although these measures are based on plausible prevention concepts and have (commonly) been implemented in recent years, their effectiveness for decreasing the risk of injury is still unclear. Once their effectiveness has been verified, additional educational activities might be required to convince coaches and athletes to wear these protective devices [
86]. With regard to head injuries, it is plausible that wearing a helmet can substantially reduce the risk of a head injury. However, in alpine ski racing where helmets have been mandatory for many years, head injuries still frequently occur [
19]. Thus, future research efforts should primarily focus on developing more sophisticated helmet standards that cover the full extent of potential impact loadings [
48]. Most recently, some improved helmet standards have been implemented within the FIS equipment regulations [
87,
88]; however, there is still room for further improvement.
‘High skiing speed’, particularly when combined with terrain transitions or small turn radii, was reported to be indirectly associated with high injury risk [
15,
17,
34,
35]. Based on this knowledge, reducing speed at terrain transitions, speed in turns, or speed in general are reasonable, etiology-derived prevention measures. From a mechanical perspective, speed is reduced when the skier turns more out of the direction of the fall line [
89], or energy is dissipated due to ski–snow friction or air drag [
90‐
92]. With regard to the latter, racing suits with increased drag coefficients have been suggested to increase athlete safety [
35]; however, for a substantial decrease in speed, not only would the suits’ permeability need to change drastically but also the suits’ cut [
93]. A prevention measure with more impact on speed might be adjustments in the course setting [
34]. In this context, speed was found to be controllable by increased horizontal gate distance (i.e. the gate offset), and by shorter linear gate distance (i.e. the direct distance between gate to gate) [
49,
50]; however, it has to be emphasized that only substantial course setting changes might be able to effectively slow down skiers [
94]. Furthermore, controlling speed by increasing the gate offset might have two major drawbacks: (i) it may increase the risk of fatigue, and (ii) it may increase the risk of out-of-balance situations [
94]. Based on these considerations, preference for course settings that locally and radically slow down skiers before terrain changes or key sections, have been promoted rather than marginally, but constantly, increasing horizontal gate distances [
94]. Interestingly, steeper terrain and modifications in equipment geometry were also found to be associated with lower speed [
49,
71,
77,
95]. With reference to steep terrain, it has to be pointed out that terrain is a given constraint for course setters, and that in steep terrain it is the larger gate offset that causes the lower speed. On the topic of modified equipment, the preventative gain of modified geometry should not be overestimated [
77]. When compared with the considerable reductions of speed that can be achieved by course-related measures, equipment-induced speed reductions are relatively small [
71,
77].
With regard to ‘inappropriate jump construction’, it has been suggested that decreased take-off speeds, flat take-off angles and steep landings increase athletes’ safety [
35,
53]. Moreover, a systematic training of tactical decisions and exercise regimes to improve trunk control during jump landings were suggested as prevention measures [
52].
The positioning/construction of safety nets have also been reported as contributors to injuries [
25,
34,
35]. As has been recently illustrated, impact simulations might be helpful tools for finding optimal net positions in future research efforts [
96]. In addition, the impact on and the impact absorption of safety nets should be further investigated and improved [
97,
98].
Finally, with regard to ‘poor visibility’, flat light and poor (blue) coloring of the track corridor and jump take-off zones were predominant factors associated with individual injury cases [
26]. Thus, it has been suggested that repeated (blue) coloration during the entire race improves the athletes’ safety [
35].