The ACL and the Skier--Part 2

Now that you have had time to digest all the scary facts from Part 1 of this post, let’s explore the ways that the risk of an ACL injury can be mitigated. I will divide these into two broad categories: 1) strategies to use on the hill and 2) off-the-hill conditioning.

On the Hill Strategies

Recall from Part 1, the study by Ettlinger et al. (1995) that described the Phantom Foot and Boot Induced mechanisms of ACL injury. Well in addition to describing these mechanisms, they also performed an experiment aimed at finding an effective means of preventing ACL tears. The authors conducted a study in which ski instructors and patrollers from 20 resorts across the US completed educational sessions exposing them to videos of ACL injuries and near misses. The purpose of this education was to assist the skiers in developing strategies to escape risky positions as soon as any are noticed. Over the course of 3 seasons, the researchers kept a tally of all the ACL injuries sustained by the participants who had completed the training and compared this number to the number of ACL injuries incurred by the staff of 22 control resorts who had not completed the training. The comparison revealed a 62% reduction in ACL injuries among those who had completed the training program.

These results demonstrate that an awareness of how injuries can occur is a powerful tool for injury prevention as it provides us with specific situations/conditions to avoid. It is likely that many of us have found ourselves in dangerous positions while skiing but were ignorant to the risk we were in due to a lack of knowledge of the risks themselves (I know I was!). Luckily, most of us get out of these situations unscathed, but all it takes is one incident to ruin a ski season.

On top of the above-mentioned findings, Ettlinger et al. also provide us with some specific recommended actions to take if you find yourself in a risky position (refer back to Part 1 of this post if you need a refresher on the danger signs of impending ACL injury).

For a Phantom Foot injury, the best course of action is to get:

1. Hands forward

2. Skis together

3. Hands over skis

For a Boot Induced injury, it is best to avoid getting yourself into the high risk position in the first place. This could mean only hitting jumps if you know the landing is good (i.e. not in a hole) and if you are confident in your ability to take and land jumps without finding yourself in a back-weighted position.

So to summarize this section, make yourself aware of the ACL injury mechanisms described in Part 1 (re-read it and look up some Youtube videos of skiing ACL injuries--hard to watch but useful…) and be more aware of your body position when you’re actually skiing. Take note of how often you find your uphill hand drifting behind you, or your downhill ski taking too much weight, etc, and make the corrections suggested above.

Off the Hill Conditioning

It is one thing to talk about getting your skis back into a parallel position with your arms forward, but it can be much more difficult to actually accomplish this when you’re off balance, battling difficult snow conditions. This is where it becomes helpful if your body is strong and primed for action. In particular, it is crucial to build strong legs and a strong core. Let’s expand on both of those body parts. But before we do, a message from your neighborhood Lawyer: the following conditioning tips are general in nature. Please consider your current level of fitness before attempting any of the exercises. If you have any doubts, it is advisable to seek professional coaching from a real-life Physiotherapist or Trainer.

Strong Legs

When we talk about ‘leg strength’ it is important to be specific in the type of strength we want to build. For a skier, there are a few aspects of strength that are most beneficial to focus on: muscular endurance, eccentric control and power.

• Muscular endurance is defined by the ACSM (American College of Sports Medicine) as the ability of a muscle to perform a large number of contractions against a low to medium resistance. To translate this to the ski hill, it’s your muscles' ability to last to the bottom of every run all day long. To improve muscular endurance, the ACSM recommends performing a large number of repetitions (15-20) of a low to moderate resistance (less than 60% of your maximum) for 3 to 4 sets, allowing only about 30 seconds of rest between sets (ACSM, 2014).

• Eccentric control is the ability of a muscle to actively lengthen. For example, when you slowly lower a heavy weight in the down phase of a biceps curl, your bicep is contracting eccentrically. Similarly, your quads contract eccentrically when you absorb a mogul (the quads lengthen when your knees bend, so when you absorb a mogul they control the speed at which the knees bend to do so). In fact, a study by Berg and Eiken (1999) showed that eccentric quads activity was particularly high among elite level alpine skiers. One great way to develop eccentric muscle control is by introducing jumps or hops into your exercise routine--for example, converting a regular body weight squat to a jump squat or a lunge to a jumping lunge. As you absorb the landings of these exercises, your muscles will be behaving eccentrically.

• Power is defined by the ACSM (2014) as the ability of a muscle to develop a large amount of force over a short period of time. Having powerful legs on the ski hill means a greater ability to quickly adapt to a variety of terrain and snow conditions. Again, adding some jumping to your exercise program is a great way to develop power. In this case, it is the powerful push as you propel yourself off the ground that increases your power.

Bullet-Proof Core

In order for your core to get you out of sticky situations on the ski hill, it needs to not only be strong but also highly responsive to sudden changes in balance.Therefore, it is not sufficient to just do planks and crunches. Effective, sport-specific core training must be incorporated into dynamic, full-body movements. For example, a standard lunge could be transformed into an effective core exercise by having a friend toss a medicine ball at you at the bottom of each rep. Or a squat could be improved by doing it on top of a half-ball. To generalize, most exercises can become core exercises with the addition of: unstable surfaces, expected disturbances (e.g. a band around your leg that threatens to pull you sideways as you lunge), or unexpected disturbances (e.g. your medicine ball hurling friend). This type of training will better prepare you to pull yourself back from the point of no return in a dangerous ski situation.

In summary, staying injury free as a skier requires you to take action both on and off the hill. On one hand, a good skier can still get into trouble if they lack the muscle strength to react to dangerous situations. Conversely, even the most muscular folks can encounter an injury if they don’t know what to do on their skis. So be attentive to your body position on the hill and get as strong as you can off the hill!

(I had previously intended to talk a bit about what happens after an ACL injury if one does occur, but in the interest of not writing a novel, I will save that for another day).

References

American College of Sports Medicine., & Pescatello, L. S. (2014). ACSM's guidelines for exercise testing and prescription. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health.

Berg, H.E. & Eiken, O. (1999). Muscle control in elite alpine skiing.

Med & Sci Sp & Ex, 31(7): 1065-67.

Ettlinger CF, Johnson RJ, Shealy JE. (1995). A method to help reduce the risk of serious knee sprains incurred in alpine skiing. Am J Sports Med. 23(5):531-537.