Locomotor biomechanics

Question 1

What is the safety factor?

Answer 1

Maximum stress a structure withstands until breakage
__________________________________________
Stress it is most likely to undergo during its lifetime

Typcially 2-4

Means how much extra force you’d need above the normal force experienced to actually fracture the tissue

Question 2

What are the factors for failure?

Answer 2

-Force/Stress

Magnitude, frequency, speed of loading, duration of loading

Question 3

What can influence locomotor failure?

Answer 3

Body mass
Speed
Gait

Question 4

What are common constraints during locomotion?

Answer 4

Minimal force needed to support body against gravity

Force only produced when limb hits ground

Question 5

What are the different types of force and what tissues do they affect?

Answer 5

1) Tension (stretching) = Tendons, bones
2) Compression (pushing together) = Joints, bones
3) Bending = Bones
4) Shear = Joints

Question 6

Which part of the limb is called the ‘biological spring?

Answer 6

Distal limb - walking on 1 finger

• stability over flexability
• low safety factors
• little scope for adaptation

Question 7

How are the distal limbs specialised?

Answer 7

Reduced muscle mass -

• Reduces swing time –> higher speed
• SDFT, DDFT, Distal accessory ligament, Suspensory ligament = Tendons efficient at energy storage
• Straight limb - no energy wastage on joints`

Question 8

How are the fibres running in flexor tendons?

Answer 8

Highly pennate -Fibres arranged in a feather like pattern (short fibres) - create a lot of FORCE

Limited capacity for length change

Question 9

How are the bones adapted in the distal limb?

Answer 9

Radius and Ulna fused - reduced bones
Increased energy storage (tendons!)
Weight bearing on the 3rd MC/MT + digit
Lengthened limb

= lighter limb, shorter swing time, less mechanical energy

Maximum strength, minimum weight

Question 10

What is the function of joints?

Answer 10

Relative movement of limb segments

Shock absorbers

Question 11

How are horses specialised in regards to joints?

Answer 11

Reduction of phalanges
Fusion of bones —> movement only in sagittal plane
Interlocking configuration - collateral ligaments

Question 12

What is the mechanical function of the Hoof?

Answer 12

Shock absorption
Support and grip
Propulsion

Also - protects sensitive structures, resistance to abrasion

Question 13

What are the protective mechanisms of the Hoof?

Answer 13

Solar surface allows heel movement
Distal phalanx suspended 
digital cushion: shock absorption/frog movement
hoof sliding - eases the impact
Rotation/translation of DIP joint

Question 14

What is the duty factor in regards to locomotion?

Answer 14

Ratio stance and stride time

Question 15

What does speed do to stance time?

Answer 15

It reduces stance time

• this means force is generated in less time creating high energetic cost
• peak limb force is increased and also the risk of injury

Question 16

What are the 4 different stages of stance?

Answer 16

1. 1st impact (large acceleration, low forces)
2. 2nd impact (low acceleration, high forces)
3. Support, loading (large vertical force) - dorsiflexion of fetlock, very tight safety factors, increase in MCP joint
4. breakover/propulsion
   All stages are critical to injury

Question 17

Which tendons are under high strain in the distal limb?

Answer 17

SDFT and suspensory ligament

Question 18

How is the horn capsule adapted anatomically to carry out its functions?

Answer 18

-Horn arranged in tubules - ideal to withstand high compressive forces (susceptible to bending forces)

Compression strength diminishes with length - need regular trimming
Collapsed/underran heels = impairment of hoof deformation +blood flow, tubules grown distal to distal phalanx