How to reduce the risk of ACL injuries in skiers. Part 2

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In Part 1 of how to reduce the risk of ACL injuries in skiers we introduced the principals behind ACL injury reduction strategies.  We looked at what the ACL is and what it does.  We also looked at the most common mechanisms that cause an ACL tear in skiers, along with risk factors for injury.

In ‘how to reduce the risk of ACL injuries in skiers: Part 2’ we will be looking at different physical components along with exercises and ideas for training .  Whilst reading this blog, it is important to remember that there is no ‘one size fits all’.  Everyone will be at a different starting point and have different strengths, weaknesses and needs.

Do you remember that in part 1 I mentioned the chap that ruptured his ACL skiing into a tree?  Well, as I said before, no amount of training will prevent some unfortunate accidents occurring.  However, training in a smart way for your skiing gives you the very best chance of staying injury free.

Ideally, you want to start to incorporate the following suggestions into your training program 2 – 4 times a week for 6 – 8 weeks before you hit the slopes.  If you are skiing all season, you can continue with most of these exercises.  However,  you will need to strike a delicate balance between making the exercises progressive whilst not fatiguing yourself before you ski.

Biomechanical positioning and alignment

Being ‘well-stacked’ on your skeleton will put you in a much stronger skiing position. This means that you will use your bones to lever from and therefore you will use less muscular energy.  This will make skiing more efficient and thus reduce the risk of fatigue related injuries.

An example of not being ‘well-stacked’ is in skiers who demonstrate an ‘A-frame’ or knocked-kneed position. This can affect skiers at all levels and can put a lot of strain through the knee joint.  This can also inadvertently make this ACL more vulnerable.

A-frame skier

An example of an ‘A’-Frame )or knock-kneed skier

The ‘A’-frame position may occur due to numerous reason and it is not always easy (or always possible) to correct.  It may arise due to a problem with boot set up or foot position, it may be an inherent position of the hips or a weakness in the gluteal muscles, specifically the gluteus medius.

Regardless of the cause, when you are skiing, if your knee is dropping inwards (‘A’-frame) then the ACL is potentially under extra strain. This position may cause an element of friction of the ACL against a bony notch and over time this may fray and weaken. Imagine a rope that is constantly under tension and rubbing against a rock. All the little fibres will begin to split and the rope frays.  If your ACL is weakened in this manner and trauma then occurs, the chances of the ACL rupturing are a lot higher.

If this position sounds like something that you may be dealing with, an assessment to work out why is highly recommended. In the meantime, many people benefit from strengthening their gluteals and you can try the suggestions below.

Alignment Squats

To check on your alignment stand in front of a mirror. Perform a single leg squat and watch the position of your knee. The middle of your knee should be directly over your 2nd and 3rd toes. If your knee falls inwards then you may need to work on your alignment.

Sometimes, just having awareness of a how to correct a squat is enough to improve it.  If you’ve noticed that your knee drops in during a single leg squat, repeat the movement whilst holding onto something for support.  Now, see if you can squat with your knee in a more optimal position.  You do not need to go very deep to start with but as the position improves you can increase the depth of your squat.

If you can correct this (and not everyone can), then over time, practice and repetition will help you to develop a better movement pattern.  To challenge yourself further stand on an uneven surface such as a wobble cushion or bosu ball.

ACL injuries in skiers

Good alignment in a single leg squat

Monster walk

The monster walk is a great dynamic exercise to get your hips and gluts working.  Place a taught length of strong theraband around your knees, ankles or forefeet.  The further down, the harder it will be – or place band around both your knees and your feet!  Bend your knees so you are in a ‘mini’ squat and side step across a room or along a corridor.  Then repeat in the opposite direction.  Continue this until your hips feel fatigued.  You can vary the depth of your squat but try not to over flex at the waist.

monster walk

Monster walk with theraband resistance

Neuromuscular and proprioceptive factors

Neuromuscular control refers to the transfer of information from nerves to muscles. In other words it is the subconscious connection between the body and the brain. It incorporates balance, strength, reflex responses and functional movement control.  We will break this down further into plyometrics, sports specific drills, strength and flexibility.

Neuromuscular training can help with muscle recruitment. If a skier is well trained they will have better strength and power to produce particular movements. Good neuromuscular control helps to generate joint movement, at the right motion, in the correct alignment at the right time. This has to be discipline specific. For example someone training for bumps will need a different program to a giant slalom skier.

Because neuromuscular training is so person specific, it is best to contact a sports physiotherapist or fitness trainer in order to have a program tailored to your individual needs.

Proprioception refers to the combination of balance, coordination and agility in order to enhance joint position and joint motion. Obviously, the better your balance, the less chance you have of falling and injuring yourself.

You can do a simple test yourself to see if you have good proprioception and balance. Ensure that you are in a safe environment. Start by standing on one leg and maintain this position for at least 20 seconds without wobbling. If this is easy repeat this with your eyes closed.  Again try and stay in a steady position for 20 seconds.  If this is hard to do, then you will need to practice further.  However, if this is easy you will need to challenge yourself with more difficult and more dynamic drills.

Skiing is not a static sport and you will need to practice fairly high level dynamic balance drills to really help make a difference.  You can incorporate single leg squats, wobble boards and wobble cushions into your training.  Lateral or side to side dynamic balance drills are particularly beneficial for skiers.

An example would be side to side touches.  Stand on one leg and reach out to touch the ground to one side of you.  Return upright and remain on one leg, then reach out to touch the ground the other side.  Vary the distance that you reach each side and vary the speed with which you perform the exercise.

Lateral touches

Side to side touches

Plyometrics and Sports Specific Skills

Plyometrics or re-bound training is exercise that is designed to produce fast, powerful movements. Good plyometrics is essential for helping joints to absorb shock. In skiers this is ideal for those that ski in the park, freestyle skiers, variable terrain and bumps where there is generally more impact than on the pistes.  Good plyometric and rebound ability can help the knee joint absorb stresses in such a way as to not stress the ACL.

Plyometric training should be sports specific. Within skiing it should be discipline specific. For example, bumps skiers will need to practice different drills to slalom skiers.

Side to side jumps

A starting point for slalom skiers would be side to side jumps with feet hip width apart (ski distance). Aim to produce a fast rhythmic jump.  You can perform this on the spot, or travel forwards whilst rebounding side to side.  Introduce a small bench to jump over for a further challenge.  Progress to performing this drill on one leg.

Tuck jumps

For bumps training, practising tuck jumps will help with fast hip and knee motion. When practicing tuck jumps think about how you perform them. Symmetrical legs, a tight tuck and a good knee bend on landing will all help to improve plyometric performance.  You will also need to avoid breaking at the waist.  Keep your torso upright as you draw your knees up to your chest.

Muscular strength and recruitment patterns

If you are not physically fit and fatigue sets in then positioning and alignment may falter, which will increase the strain on the ACL and increase the risk of falling. The stronger you are, the better your joints will be able to withstand stresses. Commonly, skiers are very strong in certain muscle groups and weaker in others.

Typically, skiers have very strong quadriceps muscles and much weaker hamstrings. In order for the ACL to work in an optimal position and to avoid an uneven tug of war between these two groups of muscles the hamstrings must be trained. There is also a reflex arc between the hamstrings and the ACL.  The hamstrings help to reinforce the ACL and therefore it is essential that they are strong in skiers.

Two of the main roles of the hamstring muscles are to extend the hip and flex the knee.  When training the hamstrings it is important to work on both aspects.

There are numerous exercises that you can do to strengthen your hamstrings including:

  • Hamstring curls
  • Deadlift variations
  • Kettlebell swings
  • Bridging
  • Nordic hamstrings

I will write about specific hamstring training in a future blog.  However, when you are training your hamstrings, think about doing a variety of different exercises.  Change the resistance and the intensity so that you are doing higher repetitions with lower weights for endurance, and low repetitions with high weights for strength gains.

Flexibility and mobility

Good flexibility and mobility allows the joints to move freely in order to meet the demands of skiing. If joints are restricted it may lead to resistance to movements and inefficient skiing.

Good flexibility of your quadriceps (the muscles at the front of your thigh) is particularly important with regards to the ACL . If the quadriceps muscles are extremely tight they can put a yank through the shin bone which causes an anterior shear force of the knee. Under this stress the ACL is at much more risk of injury.

The jury is still out regarding the science of stretching.  Research is still needed to ascertain when and how often to stretch for the most benefit.  However, I would still recommend stretching for recovery after sports and exercise.

You can stretch your quadriceps in a number of ways, but always make sure that you are warm before you start stretching. The most common way to stretch the quadriceps is to stand on one leg and take hold of your foot or ankle and draw you foot up to your buttock. Take this as far as comfortable. You should feel tension in the front of your thigh but not pain. Make sure you hold this for at least 30 seconds.

You can also stretch you quadriceps dynamically before you ski. To do this step forward on one leg and kick the heel of your opposite leg up to your buttock. Repeat on the opposite side.

In Summary

There is limited evidence for programmes designed to reduce the risk of ACL injuries in skiers.  A lot of my recommendations are based on applying the principals of injury reduction programmes from other sports to the biomechanics of skiing.

For all of the above components to ACL injury risk reduction it is recommended that you seek professional advice from a physiotherapist or trainer. Training is person specific and what works for one individual may be different to the next. If you have had previous leg injuries or if you are currently recovering from injury then it is best to seek professional advise before trying any of the exercises mentioned.

To summarise, for the huge physical, mental, emotional and economic costs it is well worth implementing ACL strategies into pre-season training. Make sure you have good flexibility, especially in your quadriceps, ensure you hamstrings are strong and make sure that you have optimal lower limb alignment.

References:

  • Ettlinger CF, Johnson RJ, Shealy JE. A method to help reduce the risk of serious knee sprains incurred in Alpine skiing. Am J Sports Med. 1995;23:531-537
  • Pujol N, Rousseaux Blanchi MP, Chambat P. The Incidence of Anterior Cruciate Ligament Injuries Among Competitive Alpine Skiers. A 25 year Investigation. Am J Sports Med 2007;35(7): 1070 – 1074

       

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