“Equine Biomechanics”

Table of Contents

Special thanks to Dr. M. Hejazi

1 Equine Biomechanics

1.1 Definition

noun, plural in form but singular/plural in construction

  1. The mechanics of biological and especially muscular activity (as in locomotion or exercise)
  2. Sience of movement of a living body, including how muscles, bones, tendons and ligaments work together to produce movement.
  3. Explains the negative impacts upon a horse's body caused by incorrect riding and training methods, such as Rollkur.

1.2 Principles (Based on Human Biomechanics)

  1. Stability
    • The lower center of gravity, the larger the base of support, the closer the line of gravity to the center of the base of support, and the greater the mass, he more STABILITY increases.
  2. Maximum Effort

    • The production of maximum force requires the use of all the joints that can be used.
    • The production of maximum velocity requires the use of joints in order; from the largest to the smallest.
  3. Linear Motion (Rectilinear) Along a straight line
    • The greater the applied impulse, the greater the increase in velocity.
    • Movement usually occurs in the direction opposite that of the applied force.
  4. Angular Motion Rotation around an axis
    • Angular motion is produced by the application of the force acting at some distance from an axis (or a torque).
    • Angular momentum is constant when an athlete or object is free in the air.
  5. Curvilinear motion Motion along a curved line

How Arena Surfaces Affect Horse Biomechanics (original video)

1.3 Muscles

  • Types of Muscular Activity
    1. IMG: (BPTH::14)
    2. Isometric Contraction
      • no joint movement (e.g. stabilizing of the vertebral column)
      • fairly uncommon in equine desciples.
      • the muscle body *may be shortened or lengthened depending on the actual length of the muscle at the time of contraction.
    3. Cocentric C.
      • shortening of the muscle.
      • result: reduction in origin-to-insertion distance.
      • concentric constraction of the extensor muscles == opening of the joint angle(s).
    4. Eccetric C.
      • muscles contract while undergoing lengthening.
      • result: increase in origin-to-insertion distance.
      • enables the horse to brake and limits closure of the joint angles during the loading phase of stride.
  • Phases of the Stride
    1. Stance Phase (weight-bearing)
      • load absorption phase (craial part)
      • mid-stance phase
      • propulsion phase (caudal part)
    2. Swing Phase (non-weight-bearing)
      • retraction phase; all the joints flex
      • protraction phase; all the joints extend
  • Muscle Groups
    1. The Forelimb
    2. The Hindlimb
    3. The Neck & Trunk

1.4 Longitudinal Movement

1.4.1 Lowering of the Neck

Regardless of the gait, lowering the neck results in several biomechanical changes; specially in forehand. Actually, lowering of the neck has got its cons and pros.

  1. Horizontalization of the head and neck results in displacement of center of mass (to forward).
  2. Increased loading of forehand
  3. Offloading of the hindquarters.
  4. Flexion of the cervical spine
  5. Opening of the cervical intervertebral foramen; provide a relieving action, particularly in horses that have nerve compression or irritation at these sites.
  1. Advantages

    Lowering of the neck results in absence/reduction of hind end engagement; Almost all of other advantages of lowering of the neck is relative to this effect.

  2. Disadvantages
    • Excessive tension on the supraspinous ligament may result in lesions of the ligament itself or at its insertions (desmopathy or enthesopathy).
    • Tension of the supraspinous ligament results in compression of the vertebral bodies and, therefore, the intervertebral discs. This can result in injury to these structures, particularly in the lower cervical spine.

1.4.2 Biomechanics of Rein-back

  • Rein-back is one of the most common gaits; particularly in warming up before events.
  • Low speed
  • Few risks to the locomotor apparatus of the horse; which is often heavily stressed by training and competition.
  • Enhances control of the balance of the horse during work; valuable educational tool in learning and development of collected gaits.
  • Rein-back is a symmetric diagonal gait without a swing phase.
  • Appropriate to evaluate the biomechanics of the forehand and the hindquarters separately.

How to Rein Back (original video)

1.5 Lateral Movements

  • Lateral movements, provide equilibrium and flexibility to the shoulder and hip and work the adductor as well as the dbductor muscles.
  • Analysis of simple movements (e.g. Half pass, shoulder-in at a trot) seams necessary in physical preparation of the horse.
  • Adduction: Limb moves towards the median plane (or opposite limb).
  • Abduction: Limb moves toward the exterior.
  • L.M. is only possible in the horse through the most proximal joints of the limbs:
    • shoulder (scapulohumeral) joint in the forelimb
    • hip (coxofemoral) joint in the hindlimb

    Lateral movements are ccompanied by a simultaneous rotation within the joint. The joints located below the shoulder and hip can only undergo flexion and extension movements; because of the shape of the articular surfaces, lateral movement is not possible in these more distal joints.

When performing lateral movements the essence must be well observed:

  1. The center of balance must be in the right place in the body.
  2. The hindlimb must step under the correct center of balance to be able to take weight.
  3. Which results in a lifting of the force hand and freely moving shoulders.

Riding correct shoulder-in (original video)

1.6 Jumping

Jumping biomechanics (original video)

World record horse high jump (original video)

1.7 References

1.8 Used tools

-- Mohamad Fadavi <fadavi@fadavi.net>