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On 22 November 2012 at 16:37 | updated on 10 January 2013 at 19:14

110 mm: stresses placed on muscles and joints

110 mm: stresses placed on muscles and joints

For lots of skaters, transitioning to 110 mm always causes several tendon and joint pains: knees and ankles are particularly put to the test. Then, transitioning to that new standard diameter requires a few precautions...

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The increase of stresses placed on muscles and joints

For a few years, the constant increase of skate wheel diameters has led to more knee and ankle load. In less than 10 years, 80 mm wheels gave way to 110 mm, which represents an increase of 37% of the diameter!Ankle's anatomy

More stress on ankle joints

With a neutral edge (flat), the load exerted on ankles is the same with 80 or 110 mm, provided that the frames are perfectly set up under the foot. On the other hand, during edging, the forces exerted on the ankles are far bigger.

 

Have we reached some physiological limits with the 110 mm?

110 mm wheels have become the standard. Is it safe for our ankles?

There is no ready-made answer. It all depends on the level of the skater and his body type. Using 110 mm wheels needs an adaptation period and an appropriate equipment.

According to the average skaters, like some elites, muscles are a lot more stimulated, ankles strain faster, weight bearings are less stable… At first, even the national and elite skaters tried to lessen the problem in opting for 3x110 1x100 frames. After a few years, athletes have reinforced their ankles and skate more and more with 4x110 mm set-ups, which is proof that a muscle reinforcement period is necessary.

Anatomy and biomechanics of the ankle

The talocrural joint (name) is a hinge-joint (type) and is composed of the tibia, fibula, and calcaneus.

The simplified movement of the joint is a back and forth rolling or a dorsal/plantar flexing.

the hinge is then composed of the tibia, which is the ceiling and the internal side, and of the fibula, which is the external side; these two bones are fixed together with ligaments enabling a slight play in the joint: interosseus membrane, anterior and posterior ligaments of the ankle.

There is no muscle at the ankle but tendons on the front (dorsiflexors, i.e. dorsal flexors), on the lateral side, on the back (Achilles tendon) and on the medial side.

Thus the joint is remotely controlled by 'reins' which manage the power of the talocrural joint. Although they are not really natural, the rolling movements (in-out) are tolerated by the subtalar joint (the joint underneath the talocrural joint i.e the "ankle").

When the foot goes up (dorsiflexion), the volume of the talus is bigger and the talocrural joint is put under passive pressure, so that the whole is more solid. The skater is in a skating phase and the joint is very stable.

During the push, the ankle starts a plantaflexion and an eversion, the volume or the talus is reduced, the joint has to tighten and the tendons of the anterior, external and then posterior muscles are going to draw the fibula and the tibia closer together thanks to their contraction!

Skater's positions

It is easily understandable why the muscular canal in front of the shin is often painful for skaters.

Picture of skater, with ankle rolling on the inside edge

The ankle supports 70% of the bodyweight (30% at the front of the foot); when you skate, your loading remains static, there is no roll-out of the foot like when you walk… Hence a constant load angulation on the ankle which is all the more tiring.

A little bit of maths?

Let a height be determined by the bone growth: tibial plateau / calcaneus tuberosity between 9 and 10 cm, 110 mm set-up implies a height = 12 cm (skate) + 10 cm (ankle), i.e. h = 22 cm, plus an alpha internal angulation during the push and external angulation during rolling phases in relation to the vertical to the ground, the formula M = F.h.sin(alpha) then gives the moment of the stress placed on the ankle.

It is interesting to know that a skater weighing 70 kg and equipped with 110 mm wheels is subjected to a twisting force at the joint of 26.7 Nm (newton-meter) whereas barefoot, the value is of 12 Nm. As a first approximation, the considered force F is postulated to be equal with the weight of the skater (let's ignore the push of the leg).

The demonstration proves that in doubling the heights (from 10 to 22 cm), the twisting forces exerted on the cartilages of the talus, tibia and fibula are multiplied by 2, whatever the value of the angle. Last but not least, for a 45° angle (sharp bend) the twisting pressure is multiplied by 1,0 compared with a walker whose ankle would lean at 10°.

With the same conditions, for a skater equipped with 84 mm wheels, the total height becomes h' = 9.4 cm + 10 cm = 19.4 cm, and the stress moment is of 23 Nm.

Thus, when you transition from 84 to 110 mm, the factor of stress increase will be h/h' = 22/19.4 = 1.13, i.e. 13% more whatever the Alpha angle.

All in all, skating with 84 mm wheels with a 30° angle is equivalent to skating with 110 mm wheels with a 26.1° angle (edging is less aggressive to cartilages in 84 than in 110 mm).

But carbon boots support and reinforce the natural joint; Stresses are thus passively reduced and become bearable with training.

Is it enough?

Moreover, the forces demonstrated above will accelerate cartilage deterioration in the long run. We lack retrospective, but in 20 years the elite generation of Gicquel, Loy, etc. may suffer from important ankle pathologies.

Nevertheless, the ankle is only one piece of the puzzle constituting the whole skating move. Indeed, the joint is at the end of the line of the lower limb, and physical stresses will be more important at the hip, the knee and at the lumbo-sacral joint.

The joint that will suffer the most will be the knee, which will do flexing rotations in order to make the transition easier from inside edging to outside edging, under a high muscular stress, which 'clings' the knee cap and the tibia on the femoral condyles, and then increases the deterioration of the cartilage.

Questions to Julien Levrard (2008 vice world champion of marathon)

Hello julien, you switched to 110 mm in 2008…

Yes, I did not feel like wasting 2 years transitioning.

Did you have any joint or tendon pain during the transition?

Julien Levrard (Rennes sur Roulettes 2008)It is true that it was hardcore! I have been skating with 110 mm since April 2008.

As soon as I am tired, my articulatory alertness decreases and my tendons (Note: in fact, ligaments) pay the price. You also have to be careful after a fall because your whole skeletal system has moved and your landmarks have changed. As a consequence, you do not find your weight bearing easily on the good parts of your foot. That is when I realized all the problems linked to ankle support.

Did you try the 3x110?

Yes, I briefly tried at the World Championships in Gijon. It is a question of height. I quite liked it, by the way. It is true that you do not need as much precision when you put your foot on the ground. You can push more easily, even if you do not push neatly. And when you are a bit tired, it also works better.

I said to myself: "If you manage to switch to 4x110 mm, you can skate with anything". I owe it to you: that it is a simplistic way of thinking.

According to me, that set-up is not recommended for skaters with weak joints or with a poor articulatory strength (ankles, knees, hips).

I think that you should do a huge work in proprioception before making the transition to such a height. Proprioception qualities vary a lot according to your body's state of alertness, that is why according to the time or the day, you can feel articulatory problems.

What do you advise?

I recommend all those balance drills on one foot with your eyes closed, hands behind your back, your foot on a cushion, etc. You should do them after a good warm-up of all your joints: ankles, knees, hips (just as they do in swimming or handball).

The general muscle strength of a skater is important with 110 mm: the more muscle tone, the faster you react to losses of balance.

Links

Interview with Julien Levrard
Apports de la podologie aux rollers sur mesure

By Thierry Feutrier (physiotherapist), Valino, Alfathor
Photos: online-skating.com & all rights reserved
Released  on 22 November 2012 - Read 58483 times


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