Lateral or medial rolling/one-side material fatigue

Posted by kyBoot Shoes on

The human body is built for walking barefoot on natural terrain. This trains and strengthens the feet with every step from day to day. In contrast, civilised man walks on flat surfaces in shoes with stiff soles or heels, impairing the movement of the foot and thus weakening it. If such a weakened foot is inserted into a kyBoot, it will probably be overtaxed at first. Lateral/medial rolling is an initial sign of this weakness.

In the kyBoot/on the kyBounder, you can build up your foot musculature again so that your feet regain power and stability and lateral/medial rolling occurs less or not at all.



With every step, your heels roll to the inside or the outside.
The kyBoot becomes soft on one side, and the rolling increases.

Possible foot malpositions and instability that could exacerbate the danger of ankle buckling in the kyBoot:

  • Flat valgus foot, flatfoot
    The condition in which the longitudinal foot arch (the arch on the inside of the foot behind the balls of the feet) is flattened is called flatfoot. In extreme cases of flatfoot, full load is placed on the skin of the sole under the longitudinal arch, or the contour of the inside of the foot is concave.

    The condition in which the back of the foot is displaced to the outside, causing the inner ankle bone to protrude prominently is called pes valgus deformity. The two conditions can appear simultaneously or in such a way that a distinction cannot be made between them.
  • Unstable ankles:
    Ankle instability can arise if the ligaments have been strained or torn and have remained too loose after growing back together (mechanical instability). Some people have naturally loose ligaments.


Because modern daily routines (with cement floors, mobility-limiting shoes and the like) scarcely train the feet, most people’s foot musculature is severely weakened. This makes the feet less stable and more prone to rolling sideways, particularly on uneven surfaces.

The kyBoot has a soft, elastic sole that allows the foot a three-dimensional range of movement. This makes improper loading (such as lateral/medial rolling) immediately apparent. The foot is much more stable in ‘normal, hard shoes’. But improper loading occurs with those as well. You can observe this on heel wear in hard soles, where it often occurs on one side only.

The soft, elastic kyBoot sole has a great advantage: it yields immediately when weight is unevenly distributed, making one-sided loading obvious to the wearer and allowing them to counteract it. The more weight the wearer puts on the kyBoot sole, the more obvious the uneven loading on the foot becomes.

In most cases, only one foot rolls to the inside or outside. Why is that?

  • Most people have a strong hand and a weak hand. The same is true of the legs and feet.
  • If a person were to walk barefoot in sand every day, both feet would be trained to exactly the same extent and would therefore be almost equally strong.
  • A person trained in this way would not roll to the side at all if they wore a kyBoot.
  • Because hard surfaces have made it easy on modern man’s foot musculature, the feet always remain weak. We unconsciously relieve the feet by engaging only one leg when standing for a long time, for example.
  • Because the unequally strong feet are challenged to exactly the same extent in the kyBoot, the differences become immediately apparent, with one foot buckling in varying degrees in relation to the other foot.

Long-term consequences

  • Overloading/improper loading of ankle and knee
  • Leads to muscular imbalances, asymmetries and painful irritation
  • Increases the risk of falling

The kyBoot is the perfect training shoe for those with very mobile ligaments or unstable ankles. You should definitely train your feet so that they become more stable and less susceptible to further injuries.

Conventional therapy

  • Orthopaedic insoles are often prescribed to passively stabilize unstable, weak feet. 
    Stabilizing, confining shoes do exactly the opposite: The foot is scarcely able to roll over and becomes increasingly weak. This leads to malpositions such as pes valgus deformity or hallux valgus and joint overload.
  • In physiotherapy, foot and lower leg muscles are actively and equally strengthened with exercises.

The kybun principle of operation – being proactive

If you have unstable ankles with loose ligaments or experience lateral/medial rolling in a first-generation kyBoot sole, we recommend that you buy a second-generation kyBoot with its broader, uniform sole. You will feel much safer on this sole!

It is true that the kyBoot does not give the foot much support, but that is intentional. The soft, elastic kyBoot sole allows the foot to move freely, strengthening the weakened foot musculature. Because we are not accustomed to this freedom in our normal, hard shoes, we initially perceive the new feeling as instability, which can even be unpleasant. But this only shows us that our foot and leg musculature has become weak over the course of years.

In the kyBoot, the foot relearns how to roll naturally from the heel, which makes it stronger and more mobile. The initial unstable feeling in the kyBoot/on the kyBounder will go away after a few days or weeks as your ankles become more active and the musculature stronger. That will allow you to keep your balance better in the kyBoot/on the kyBounder – even on uneven terrain.

Wearing the kyBoot every day will decrease the stability and power difference between the two feet, even if it never goes away entirely – in the same way that a left-hander can never train their right hand to be quite as good as the left. In the feet, which are the body’s foundation, it is very important that differences between left and right be corrected; otherwise, relieving postures will develop, possibly triggering back, hip, knee and foot problems.

Initial reactions

Specific initial reactions with unstable ankles:

Lateral/medial rolling in the kyBoot over a long period of time can lead to pain and irritation in the foot or on the side of the knee or hip. It is therefore important to prevent lateral/medial rolling and actively correct the foot position.

Click here for the general initial reactions experienced by kyBounder and kyBoot beginners

kybun exercises

For information about the special kyBoot exercises or the basic kyBounder exercises , please click here.

Application tips

In the beginning, it is important to ensure a correct foot position in the kyBoot. This means that the foot should remain straight on the kyBoot sole without lateral/medial rolling. Any lateral/medial rolling in the kyBoot is not the fault of the kyBoot, but is caused by foot weakness, which must be gradually reduced through training. You will notice immediately when you place one-sided strain on your feet because the sole yields greatly in the corresponding area.

Try to focus on the foot position and correct lateral/medial rolling; this strengthens your foot musculature, which will in time prevent lateral/medial rolling of the ankle joint. Make sure that your body does not cramp up.

Be sure not to take steps that are too long, since this makes it easier to stabilize the foot over the kyBoot sole and reduces the tendency towards lateral/medial rolling of the ankle joint.

If walking upright in the kyBoot is no longer possible or you notice that you are ‘standing beside the shoe’ and are unable to correct this any longer, take this as a sign of body fatigue that means that you should take a short break from the kyBoot.

Gradually increase the duration of use at your discretion until the strength and coordination of your feet is sufficient for walking in the kyBoot for several hours at a time. For some people, this is possible after just a few days, while others take longer. It is highly individual.
The kyBoot is a training device and can, but does not have to, become an everyday shoe later.

If your foot musculature is very weak, it may make sense to make your first kyBoot a model with a second-generation sole. This sole is more stable in the midfoot section. (Please consult your kyBoot dealer for further information.)

Try various kyBoot models; some models with a higher cut provide more stability.

If you still feel too unsafe walking in the kyBoot, we advise using the kyBounder. The kyBounder is available in three different thicknesses. This allows you to choose the thickness that is most comfortable for you (the thicker, the more unstable, the more intensive the training).
You can also hold on to a fixed object if you need additional support when using the kyBounder.

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