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Muscles, Mechanics and Movement

The HORSES INSIDE OUT Conference 2010

Held in Grantham at the Ramada Hotel and Arena UK this conference looked at aspects of Core Stability, Muscular Imbalance, Training, and Biomechanics in both horse and rider. The first day was led by Dr. Hilary M. Clayton, widely considered the world's leading researcher in equine locomotion and biomechanics, Director of the Mary Anne McPhail Equine Performance Centre, Michigan State University, vet, researcher, rider, trainer with a unique perspective on the athletic horse and  the interaction between horse and rider. Hilary’s main field of interest is gait analysis which she studies with the use of reflective markers attached to the horse. Using modern computing techniques these are converted to a ‘stick figure horse’, are tracked, and then presented as useable data.
Hilary also uses a force plate which measures the ground reaction forces as the foot weight bears enabling her to study the function and movement of the force. A selection of the topics covered were:

Function of the Limbs

By comparing the horse to an elephant and a cat, Hilary demonstrated how the angulation of joints within the limbs affects function and movement. Because an elephants’ limbs are designed to be weight bearing, they are pillar like with little angulation to the joints. Elephant’s paces have no suspension phase and their fastest gait is a running walk. Cats on the other hand have highly angulated limbs providing them with the ability to them to crouch and spring and move at speed.
Horses lie somewhere between the two. Greater angulation is seen in more athletic horses whereas those with more upright the limbs are better suited to weight bearing. The forelimb joints are less angulated than the hind because their function is to carry more weight. They act as struts, controlling speed, direction, the position of the forehand, and when jumping.
The hindlimb joints are much more angulated and therefore they provide propulsion – by flexing then pushing.

Horses have long limbs, with the weight of muscle high up the leg and close to the axis of rotation. This enables them to fulfil their function to move at speed. Hilary also offered insight into one aspect of lameness. A horse double the height of another will be six times as heavy without a comparable increase in the strength of the supporting structures. This means in general, ponies and smaller horses are easier to keep sound than larger ones.

Ground Contact

A hoof hits the ground either flat, toe or heel first. Slight heel first contact is the ideal as this evens out the impact and stimulates proprioceptors in the frog and heels. If the Hoof Pastern Axis (HPA) is broken forwards there is an exaggerated heel-toe placement. If the HPA is broken back this results in a toe first contact which results in a greater degree of tripping and increased strain on the Deep Digital Flexor Tendon. It is important that hooves are trimmed to achieve balance. Studies in Michigan, Utrecht University and the Royal Veterinary College have shown that the hoof tends to land lateral side first.

Limb Support in the Stance Phase

There are two types of tendons:-

  1. Positional Tendons

These are inelastic and remain a constant length. They do not stretch when the parent muscle contracts. These tendons are responsible for precise movements.
In the horse the Deep Digital Flexor and the extensor tendons are positional tendons and contribute to positioning the hoof for ground contact. The small wobble seen by the hoof just before ground contact (more easily viewed in slow motion video footage) is attributable to these postural tendons in the lower leg.

  1. Elastic Tendons

These stretch when loaded and recoil when released. This energy saving technique  is very useful in locomotion. Hilary gave the example of that the achilles tendon in the Kangaroo reduces the energy required for jumping by 50%!

The elasticity of the superficial digital flexor tendons and the suspensory ligaments which run down the back of the leg provide a supportive sling around the fetlock joint. When the limb is fully extended and weight bearing, the fetlock sinks down. This stretches the superficial digital flexor tendon and suspensory ligament which when released recoil. This results in flexion of the lower limb. The amount the fetlock sinks is dependant on the vertical forces (measured on the force plate). This increases with both speed and weight thus making the structures more susceptible to injury. Due to inefficient repair in elastic tendons, micro-damage accumulates with age. This can be compared to complete or partial rupture of the achilles tendon in people over the age of 40! It is therefore very important to check horses legs for heat and inflammation on a regular basis.

 

Question and Answer Session
At the end of the day Hilary was asked which studies had benefited her most as a rider? She answered that truly understanding the gaits so they became second nature has allowed her time the application of the aids to maximum advantage and a thorough understanding of how the position of the head and neck affects balance has been an enormous help. Because of the high proportion of muscle, the head and Neck account for10% of body weight which means there is a 1:10 mass ratio head and neck: to body. In practical terms this means that the head and neck have to move 10 cm before it can affect the centre of mass by 1 cm. Another application of study to riding is that because the horse’s base of support is so small it is important to be still and stable. Studies have shown that it is easier for a horse to carry a sack of potatoes than a rider, so next time someone tells you, you are riding like a sack of potatoes – take it as a complement!

When asked, what has been the biggest surprise from her studies, Hilary replied, discovering that the Piaffe has no moment of suspension!
Other topics examined during the day included and the importance of keeping muscles in optimum condition*

In all topics covered and in line with the Horses Inside Out philosophy of  the practical application of anatomy and biomechanics to movement it can be concluded that the more we can understand ‘How the Horse Moves’* the better we can improve performance and reduce the risk of injury.

*see www.HorsesInsideOut.com for books and DVD on these topics.

The second day was held at Arena UK, Allington and was led by Andy Thomas, physiotherapist to team GBR and lead practitioner for Human Science and Sports Medicine for the British Equestrian Federation. Andrew specialises in musculo-skeletal injury prevention with elite and amateur athletes identifying rider problems contributing to common rider errors. He works with riders from all disciplines.

Within equestrian sport riders often seem to appear reluctant to address their own muscular skeletal problems. Recognising this, Andy set up a mobile physiotherapy clinic in a purpose built converted lorry in 2002. This enables him to watch riders on their horses and then offer immediate physiotherapy support at events and at their own yards thus saving them saving them time and expense.

Andy has developed his own unique approach to equestrian physiotherapy aspects of which  he shared with Horses Inside Out on Sunday. Andrew recognises the importance of functional therapy so for example a footballer would be treated very differently to a rider.

What Makes a Good Rider?
Andy first explored the question of what physical attributes make an ideal rider and what physical differences one would expect to find between riders from different disciplines. For example, one would expect a top dressage rider to walk with poise whilst an eventer on the other hand may well walk with a limp!

Suppleness, balance, flexibility, agility all need to be present in riders but need to be considered in relation to function – does a rider really need to be able to touch their toes for example?

In the course of his work, Andy has identified that those with the best balance have ridden a variety of different poise and horses from an early age, have hunted, not specialised too early and have taken part in other sports. For example both Laura Bechtolshimer and Emma Hindle both played Hockey to National Level.

Suppleness, balance, agility need to be practised as children in order to reach full genetic potential as an adult.

Imbalances and Weaknesses
Before beginning to work on strengthening core muscles in the rider it is important to first identify and then correct any imbalances and weaknesses.

With riders the hip and pelvis needs to be the primary focus as this is in contact with the saddle and controls the seat. With runners the primary focus would be the feet as they are the contact point within their sport.

Most riders have some form of weakness or imbalances for which the body will compensate.
Generally this involves either holding muscles rigid or by allowing the body to become over loose. This can be seen as a hip collapsing, back becoming hollow or loose, one leg swinging to one side or a fixed knee, shoulder or arm. The result of compensation is often pain- in the back, neck or hip, or there may be an inability or reluctance to perform movements in accordance to the wishes of the coach.

Three main patterns of imbalances and weaknesses can be identified in riders’ pelvic and hip region.

  1. The rider becomes tight on one side (internal rotation of the hip is reduced) and weak on the opposite side (lateral stabilising muscles of the hip ie gluteus medius, biceps femoris). This pattern is often seen with young riders.
  2. The rider is tight and weak on the same side. This tends to be a more complicated scenario; compensation patterns are harder to predict and this pattern is harder to identify. It tends to develop with more experienced riders as they try to hide their weakness and so tightness develops on the same side.
  3. The rider becomes weak on both sides. This results in an exaggerated range of movement. with little stability or control. This scenario tends to be seen in young long gangly females and most often results in lower back or pain in the thoracolumbar region. These riders will often ride with a head nod!

 

Stability

The development of the key core muscles around the trunk is the most important factor in rider stability. This provides effective distribution of force and pelvic control during movement and allows independent limb control.

It is easy to understand why cross country riding requires good core strength, but it is also essential for dressage riders. Emma Hindle and Laura Bechtolshiemer have the best core strength out of all the riders Andy works with.

There were two event and two dressage riders at the Horses Inside Out Conference their ages spanning 4 decades.

To begin with Andy assessed the riders, unmounted, for imbalances and weaknesses releasing any tension with soft tissue release work. He then looked at them on their horses so he could demonstrate how their imbalances, weaknesses, pelvic mobility and core strength affected their riding.

 

A Ridden Test for Weakness of the Muscles that control the Hip Joint
A good test to identify hip weakness is to ride  without stirrups lifting the legs alternately away from the saddleand  noting whether the rider leans excessively as each leg is lifted to the side

A Test of Core Stability
Noting the degree to which riders grip the knee rolls, or wobble as they ride transitions is a simple but effective test of a weak core.

Pelvic Mobility
With all the riders Andy focussed on the ability of the rider to move the pelvis in synchronously  with the horse’s movement. It was interesting to see that most of the riders were compensating and using other areas of their body to absorb the horse’s movement. For example – hyper mobility of the thoracic spine, a head nod or appearing to fix the shoulders and arms.

Good pelvic mobility allows an independent seat and independent use of other body parts. To improve pelvic mobility Andy asked the riders to dismount then sit on a swiss ball, or on the Eckhard Meyners stool to encourage them to move their pelvis’ through their full range of movement. This helped to activate the appropriate muscles and  proprioceptors and to stimulate the nerves. This simple but effective technique really did make a difference to all of the riders and it was suggested that we should all try doing this before riding as part of our warm up routine – we all could do with keeping a swiss ball in our lorries!!

The range techniques and tests Andy showed for addressing rider imbalances and weakness, pelvic mobility and core strength were very useful not only for therapists also something that all coaches can perform with their riders.

All in all this was a most successful, informative and interesting conference with very positive feedback and requests for something similar in the future.

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