Something I learned only a few years ago came as a rather surprise – namely that the calf muscles work hardest as your foot hits the ground and not as you push off!!

Another thing that I did not fully appreciate was the role of the Achilles heel tendon in controlling movements at the subtalar joint.

To explain this requires going into some detail about what happens during the running gait cycle and also a quick resumé of the subtalar joint.

The Running Cycle

The running cycle consists of 3 phases

1. stance
2. float
3. swing

Look at the 3 phases for the RIGHT leg below:

(Hover over the picture with your mouse for the picture title)

I am only interested in the stance phase for now. This phase has 3 markers

1. initial contact – when the foot makes first contact with the ground
2. mid stance – when the knee and ankle are at their maximum flexed angles
3. toe off – when the foot loses contact with the ground

These markers give us two sub-phases of the stance phase

1. ABSORPTION – storing the landing forces in the tendon and muscle
2. PROPULSION – using the stored landing energy to propel the body forwards

Subtalar Joint

The subtalar joint is the lower portion of your ankle area. Your ankle (talo-crural) joint allows dorsiflexion and plantarflexion movements. The subtalar joint allows inversion and eversion of the Calcaneum on the Talus. When the joint between the Talus and the Navicular bones (Talo-Navicular joint) is included then you get Supination and Pronation of the hind -foot at the Talo-Calcaneo-Navicular joint.
If any of these terms are confusing see Foot Fundamentals and Ankle Joint – a balanced view.


The subtalar joint is a very complex joint. If you look at the picture on the left this is the foot with the leg and the Talus removed. You are looking down on the Calcaneum and forward to the Navicular bone. The blue areas are the joint surfaces where the Talus joins with the Calcaneum and the orange where it joins with the Navicular bone – you can see the complicated nature of the joint.

Look at the video below and check the complicated movement at the subtalar joint.

If you draw a line through the axis of rotation of the Talo-Calcaneo-Navicular joint (the red line in the diagram of a right foot) then the Achilles tendon attaches medial (inside) to this axis (green area in the diagram).
The importance of this is that it helps to produce supination at the subtalar joint – you can see this in the diagram.
Imagine if you were to pull on the green area – the Calcaneum will tilt inwards and upwards (supinate the hind-foot).
If you now imagine landing on the outside of your heel then you can see how your Achilles heel tendon can help to control the rate at which your hind-foot pronates (slows the Calcaneum tilting outwards and downwards).

Achilles and Running Gait

Initial Contact -

The hind-foot is inverted by about 10 degrees.
The ankle is in 10 degrees of dorsiflexion.


As described above the position of the attachment of the Achilles heel tendon to the Calcaneum means that the Soleus muscle stabilises the lateral foot onto the ground as it lands in a supinated position.


In other words it stops the heel and foot from collapsing down into pronation.
It doesn’t matter whether you land on your heel or nearer the front of your foot the action of the Achilles is the same.

Absorption Phase -

During the absorption phase the foot pronates and becomes flexible.

To achieve this the hind-foot everts through to 10 degrees of eversion with the Achilles controlling this movement of pronation at the Subtalar joint by continuing to act as it does above.

The ankle dorsiflexes further to 20 degrees of dorsiflexion – the Soleus muscle decelerates this forward movement of the leg on the foot.
To understand this think of it this way :-

• if the muscle contracts with your foot off the floor it points your foot down
• if your foot is fixed on the floor then the same contraction now will take your leg backwards on the fixed foot OR in this case slow it going forwards…

Does that make sense?

Propulsion Phase -

During the propulsion phase the role of the Gastrocnemius and Soleus muscles is to control the joint positions.
Creating stiffness here allows the tendons to recoil and release their stored energy.
The Subtalar joint supinates to provide a rigid propelling lever through the action of the Achilles heel tendon.
At propulsion the Soleus slows tibial momentum forward (this would increase the ankle dorsiflexion).


The Gastrocnemius helps produce knee flexion which creates forward movement.
Gastrocnemius simultaneously plantarflexes the ankle, flexes the knee and supinates the Subtalar joint.

At toe off the ankle is plantarflexed to 25 degrees.

Summary

You should now a good understanding of

• the 3 phases of the running gait cycle
• what the Stance Phase is
• structure of the Subtalar joint
• what pronation and supination of the hind-foot are
• what the Absorption Phase does
• what the Propulsion Phase is
• action of the Achilles heel tendon during each phase
• how elastic recoil of the Achilles heel tendon provides energy to walking and running

In this post I will give you enough information to understand something quite complicated – namely how your ankle and foot work together for support, balance and movement.

I have previously explained why it is essential to have good mobilitiy and muscle control in your foot – Foot Fundamentals

I have also explained in Ankle Joint – A Balanced View how your ankle actually consists of three joints.

Ankle Joint Complex

1. The joint between the two long bones – the Tibia and Fibula (Inferior TibioFibular Joint)

2. The joint between the Tibia / Fibula and Talus (TaloCrural Joint)

3. The complex joint between the Talus and Calcaneum (Subtalar Joint

In addition to these joints you have also to take into consideration the joints between the hind-foot and the mid-foot and the mid-foot and the forefoot.

HindFoot and ForeFoot Joints

B-Joints between mid-foot and forefoot

A-Joints between Hind-foot and mid-foot

Conjoint Rotation

The combined movement at all these joints taken together is known as Conjoint Rotation. This means that as the inner arch is flattened the leg rotates inward, and as the arch is raised the leg tends to rotate outward.

Click on the video and watch it a few times – you should get the idea.

So to put it the other way round – as your shin rotates inwards your arch flattens.

You can now see why it is crucial to have control of your arch and to be able to balance effectively. If your foot is unable to move in this way it has a huge impact on movement further up your leg especially at the knee and hip.

The reverse is also true – if you do not have hip control then inward rotation of your thigh will cause a flattening of your inner longitudinal arch. You are starting to understand how everything links to everything else – that’s why it’s called the kinetic chain – everything is linked together!

That explains why

can all be caused by a weak foot and ankle.

Also why

can all be caused by a weak hip muscle.

Perhaps now you are starting to understand the complicated inter-relationships that occur when we walk and run. You can now see how it is important that all the components of the kinetic chain are functioning efficiently. That is the keystone upon which the rationale behind “diyinjuryrehab.com” is constructed.

COMING SOON …
Video Self-Assessment of your Kinetic Chain

In sport the ankle joint is the most important joint in the body. It is the key joint and is responsible for the transfer of forces from the leg to the ground. It has to cope with changes in load, speed, direction and uneven surfaces all at the same time.

To be able to run about and take part in sport efficiently at any level you have to be able to control your ankle joint effectively. Control at the ankle joint is defined as the ability to balance your moving body over your foot as the foot moves over the ground.

By the end of this article you will have:-

• a good knowledge of the anatomy of the ankle joint
• know what movements take place at the ankle joint
• have an understanding of what proprioception is
• an understanding of how you balance at the ankle joints.

Ankle Joint Anatomy

To achieve balance the ankle joints have to work in harmony with the leg and the foot. I say ankle joints – plural.

It is more of an ankle complex consisting of a collection of joints as can be seen in the X-ray.

There is the joint between the two long bones of the lower leg – the thick Tibia and the thinner Fibula. This is the Inferior Tibio-Fibular Joint or High Ankle Joint

These two bones join together to provide the mortise or socket of the ankle joint.

Fitting into this socket is the Talus bone from your foot. If you remember from “Foot Fundamentals” this is the bone that sits at the apex of the inner longitudinal arch of your foot. This joint provides the link between your foot and leg and can be considered the ‘upper part of the ankle joint’

Situated below the Talus is the heel bone – the Calcaneum. The joint between the Talus and Calcaneum is called the Subtalar joint and it can be considered as the ‘lower part of the ankle joint’. This is quite a complicated joint with movements taking place in more than one direction simultaneously.

Ankle Joint Movements

The ‘upper ankle joint’ operates similar to a hinge providing up and down movement. The upward movement of the foot on the leg is called dorsiflexion, and the downward movement of the foot on the leg is called plantar flexion.

Performing plantar flexion in standing is the same as raising your heel and standing on your toes. As well as dorsiflexion and plantar flexion there is a tiny bit of side to side movement available in the joint but this is negligible.

At the ‘lower ankle joint’ when the foot is off the ground the inward movement of the heel is called inversion, and the outward movement of the heel is called eversion. The movement at this joint takes place in three directions simultaneously and this starts to complicate things when the foot is on the ground. See Ankle and Foot – a twisted relationship for a fuller explanation.

PROPRIOCEPTION

To balance at your ankle you need to be in control of these movements at all times. This is achieved by contracting the appropriate muscles at the correct time, for the required duration and intensity. All this is under the control of your brain. To control these elements the brain needs information from the area before it can decide what response to make. This information to the brain has been called your sixth sense, proprioception, and it works alongside the other five of Touch, Taste, Smell, Hearing and Sight.

Proprioception is described as the body’s ability to sense movement within joints and joint position. A simple example would be to close your eyes, stretch out your arm to the side and then bend your elbow to touch your nose with the point of your index finger. Although you take this for granted there many, many complicated processes involved in doing this.

You have the ability to sense where your shoulder and upper arm are, how much force to supply to your shoulder muscles to stabilise your upper arm and control its rotation, you then have to bend your elbow, rotate your forearm, position your wrist, select your index finger and then place it accurately enough to touch the small target of the point of your nose without poking your eye out! Not to mention what your torso and lower limbs must do to compensate for you moving your arm. Quite Remarkable!

This is achieved by processing information from specialised sensors in your muscles, your joints, your tendons and your skin followed by your brain responding to this input by supplying signals to the appropriate muscles at the correct instant.

If you now stand on one leg you are using your proprioception sense to control the muscles around your ankle and foot joints. A reminder of the main muscle groups crossing the ankle joint is shown below.

In addition to using the feedback from your ankle area you also use input from your eyes and your ears to balance. You may find it difficult to understand why your ears are involved in balance, but you may have experienced loss of balance with ear infections or coming off a ride at a fun fair, this input to the balance mechanism is provided by fluid-filled canals in your inner ear.

Your eyes are also a major contributor to balance. To demonstrate the input from your eyes – stand on one leg and get your balance, then close your eyes. Feel how much more difficult it is with your eyes closed!

In standing your bodyweight passes in front of your ankle and it is mainly your calf muscles which control your sway backwards and forwards. When standing on one leg, if your weight (or more correctly centre of gravity) falls to the outside of your foot then you use the muscles on the inside of your ankle to correct this. Likewise if your centre of gravity falls to the inside of your foot then you use the muscles on the outside of your ankle.

Imagine you and a partner trying to control a giant telegraph pole between you when you each have a guy rope attached to the top of the pole and you’ll get the idea of working together. When the pole moves towards you, your partner has to pull, but then the pole moves towards them and you have to pull and so on…

You now have an understanding of:-

The next post will deal with the more complicated combined movement of the foot and ankle together and how this affects your running.

Now read Ankle and Foot – a twisted relationship

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