Introduction to Biomechanics

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Introduction to Biomechanics
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Introduction to Biomechanics

• This is one of the youngest forms of equine
  exercise physiology.
• Split into 2 aspects
• Kinematics study of movement, describing the 3
  dimensional linear and angular displacement of
  the limbs
• Kinetics study of forces that are generated or
  absorbed to cause or resist movement

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Introduction to Biomechanics

• Why study equine biomechanics?
• Develop methods for predicting performance
• Develop sensitive and quantitative systems for
  lameness detection
• Test the efficacy of treatment strategies
• Quality of recovery
• Equine welfare

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Introduction to Biomechanics

• Ways to study biomechanics in horses
• Kinematics uses
• Cameras
• Video
• Specialized tracking equipment
• Kinetics uses
• Force plates
• Accelerometers
• Equimost
• http//www.equimost.com/

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Introduction to Biomechanics

• Studying the gaits
• Measurements must be
• Reliable and reproducible
• Sensitive to detect time of events that are
  indiscernible to the naked eye
• Ex time elapsed between heel lift-off and toe
  lift-off at the end of a stance.
• Equipment must not actually interfer w/ or resist
  the gait in any way.

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Introduction to Biomechanics

• Kinetics and force plates
• Used to study the forces the limb applies to the
  ground and hence the forces the ground applies on
  the limb.
• Usefulness
• Determine the symmetry of the right and left limb
  pairs in weight bearing and propulsive actions
• Assessment of foot balance

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Introduction to Biomechanics

• Force plates
• Ground reaction forces (GRFs)
• Force plates measure the force applied to the
  plate in 3 directions
• Mediolateral (Fx)
• most variable
• Craniocaudal (Fy)
• Vertical force (Fz)

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Introduction to Biomechanics

• How does it work?
• Forces are given in Newtons (N/kg bwt.)
• 2 Fy phases are measured during a stance
• First half breaking or decelerative
• 2nd half accelerative or propulsory
• Crossover between the 2 phases
• Occurs when the cannon bone is vertical

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Introduction to Biomechanics

• Accelerometers
• Measures the acceleration and deceleration
  produced during limb movements.
• Can be attached to various parts of the horse
• Limbs
• Hooves
• Can measure unlimited strides
• Measures both kinematic and kinetic data

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Introduction to Biomechanics

• Studying Kinematics
• Easiest way method video camera
• VHS and Digital
• 25 fps vs 200 fps
• Skin markers
• Easier to measure
• Particular joint angles
• Linear distances
• Software programs are now available
• Methods of capture
• Moving vehicle
• Pan the camera
• Horse on treadmill

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Introduction to Biomechanics

• Stride length and stride frequency
• Stride length (SL) m or ft
• distance traveled by the horses center of mass
  during one stride
• Distance between successive prints of the same
  foot.
• Stride frequency (SF) strides/s
• Number of strides per unit time

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Introduction to Biomechanics

• How to calculate
• Speed (m/s) SL (m) x SF (strides/s)
• Stride duration (s) 1 / SF (strides/s)
• Increase in speed
• Increases stride length first
• Walk 2 m or 6.5 ft
• Gallop 6-7 m or 19.7- 23 ft
• Followed by stride frequency
• Maximal SF 2-2.5 strides/s

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Introduction to Biomechanics

• The gaits
• Particular pattern of footfalls
• Main gaits
• Walk
• Trot
• Canter
• Gallop
• 2 main types of gaits
• Symmetrical gaits any gait in which placement of
  the left and right fore and hind limb pairs are
  evenly spaced in time
• Walk
• Trot
• Asymmetrical gaits
• Canter
• Gallop

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Introduction to Biomechanics

• Walk
• Is a 4-beat gait
• Footfalls occur
• Left hind (LH)
• Left fore (LF)
• Right hind (RH)
• Right fore (RF)
• 2 limbs are in stance phase at any one time
• No period of suspension
• Most stable gait

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Introduction to Biomechanics

• Trot
• Is a2 beat gait
• Footfalls occur (trotter)
• LH and RF together
• RH and LF together
• Trot diagonals
• Are name Lt and Rt according to the forelimb
• Trot should have suspension

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Introduction to Biomechanics

• Canter
• Is a 3 beat gait with one period of suspension
• Footfalls depend on leads
• Rt lead
• RF and RH are the last pair limbs to hit ground
• LH, RH and LF together followed by RF
• This is followed by a period of suspension before
  LH impacts again.

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Introduction to Biomechanics

• Canter
• As speed increases
• Diagonal pair dissociate
• Hind limb impacts in advance of diagonal forelimb
• Gait goes from a 3 beat to a 4 beat
• Gallop
• Collected canter
• Often does not have a suspension phase
• Are 4-beat gaits
• Energy costs may be greater

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Introduction to Biomechanics

• Gallop
• Is a 4 beat gait
• Footfalls for Rt lead
• LH, RH, LF, RF
• Lead change
• RH, LH, LF, RF
• Rotary gallop
• LF is at risk of an over-reach injury
• Frequent changes
• Injury
• fatigue

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Introduction to Biomechanics

• Gait transitions
• Who determines the point at which a transition is
  made?
• Rider
• Energy costs
• Froude number
• Peak vertical force
• Jump stride
• Factors the influence the kinetics and kinematics
• Speed approach
• Height of the fence
• Rider on the approach and over the fence
• Effect of related obstacles

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Introduction to Biomechanics

• Spinal kinematics and back problems
• Introduction into Sports Medicine or Sports
  Therapy
• Back pain in horses
• Caused by many factors
• Result in significant loss of performance
• Most common injury
• Soft tissue injuries
• Vertebral lesions

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Introduction to Biomechanics

• Primary function of the spine
• Support and frame work for muscles and ligaments
• Transmitting the propulsive forces of the hind
  limb through the forehand
• Types of movement
• Lateral flexion
• Dorsiflexion
• Ventroflexion
• Axial rotation

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Introduction to Biomechanics

• Bow and string
• Suggests how the spine is affected by the limbs
  muscles and how the spine supports the mass of
  the body