This document discusses biomechanics and its application to animal movement and physiology. It begins with definitions of biomechanics and its history. It then discusses topics such as statics versus dynamics, muscle fiber arrangements, centers of gravity, and the effects of muscle attachment positions on mechanical advantage and velocity. Joint positioning and its effects on function are also examined. Biomechanics is applied to fields like orthopedics, tribology, and lameness treatment.

1. VETERINARY COLLEGE HASSAN
VETERINARY ANATOMY
SUBMITTED TO:
Dr.Rajashailesh N M
HOD
Dept. of Veterinary Anatomy
BIOMECHANICS

2. Biomechanics is the branch of science which deals with the
application of mechanical principles to the biological
systems like human, animals, plants, organs and cells.
The word biomechanics developed during the early 1970s,
describing the application of engineering mechanics
to biological and medical systems
Biomechanics

3. HISTORY
Aristotle wrote the first book on biomechanics, De Motu Animalium,
or On the Movement of Animals.
He not only saw animals' bodies as mechanical systems, but pursued
questions such as the physiological difference between imagining
performing an action and actually doing it.
Leonardo da Vinci was recognized as the first true biomechanician,
because he was the first to study anatomy in the context of mechanics.
Studied musles origin and insertion and joint movements
Studied musculature system to design machines

4. • G A Borelli studied walking, running, jumping, the flight of birds, the
swimming of fish and even the piston action of the heart within a
mechanical framework.
• He determined the position of the human center of gravity of human
body
• In the 19th century Étienne-Jules Marey used cinematography to
scientifically investigate locomotion.
• He opened the field of modern 'motion analysis' by being the first to
correlate ground reaction forces with movement

5. STATICS AND DYNAMICS
• Biomechanics includes the principles of statics and dynamics.
• Statics is defined as the principles of construction of different body parts
that result in maintaining the equilibrium of the body both during rest
and in movement.
• Dynamics refers to the movement of the body parts during locomotion.
• The construction of different body parts vary between the species
according to their living status in the environment.
• For example, carnivores, being predators, must run fast with a short
period of time in order to catch their prey.

6. • Whereas the body parts of the herbivores are constructed in such a
manner to bear the heavy weight of the contents of the body cavity
(takes large quantity of poorly digestible food) and also enable
continuous movement for long distances while grazing.
• However, though horse is an herbivore, it is able to run fast and carry
heavy loads for a longer period of time without fatigue due to the
development of passive support mechanisms.
• Whereas these supportive mechanisms have not developed in dog,
because they have a lower body weight and takes highly digestible and
high energy diet.

7. • Statics refers to stationary support, dynamics refers to movement. Most
muscle tendon systems serve both functions.
• Static analysis of material strength is commonly done by civil and
mechanical engineers and has been applied to biological materials such as
bone and tendon. The properties usually measured are:
• 1. compressive strength – how much force must be exerted to crush the test
material
• 2. tensile strength – how much force must be exerted to pull the material
apart
• 3. shear strength – how much force must be applied in offset directions to
cause a material to split in half (to shear)
• The stay apparatus of the horse is probably the best example of a structure
designed for static function. That is, for support during rest.
STATICS AND DYNAMICS

8. • Dynamic function requires greater muscle mass, hence the hind limb
which is designed for thrust, is twice as massive as the forelimb.
• The check ligaments allow the digital flexor muscles to rest during
static function.
• During the support phase of motion the check ligaments work
together with active muscle tension to withstand momentary high
stress as body mass passes over the supporting fetlock.

9. • Kinesiology is the study of animal motion. It is studied by an analysis of the geometry
of limb positions or by a measurement of forces.
• Kinematics is the study of the geometry of motion.
• Study of the moving horse spurred the initial development of motion picture technology.
• Until recently, quantification of cinefilm was an extremely laborious technique
requiring frame by frame tracing of limb positions to provide digitized data for computer
analysis.
• Video analysis now allows this process to be done automatically.
• Angle/angle diagrams usually involve a comparison of the changes in joint angle of
adjacent joints.
• If a joint is painful its range of motion will be decreased and the angle/angle diagram will
appear different than that of normal joints (shortened stride length)

10. • Kinetics refers to the study of forces.
• Methods used here include force plates that measure rapid changes in
the force applied to a plate as the foot strikes it.
• Pain will cause an animal to step softly and hence less force will be
recorded by a force plate.

11. Muscle Types
• . Antigravity muscles serve both static and dynamic functions.
• The quadriceps muscle, for example, prevents collapse of the stifle joint during
standing but extension of the stifle joint contributes to thrust during
movement. The antigravity muscles include:
• 1. Extensors of proximal joints.
• 2. Digital flexors support the fetlock. When these tendons are stretched due to
overexertion downward translation of the fetlock will occur, and if severe can
result in fracture of the proximal sesamoids. Afterwards, swelling results in
bowed tendons.

12. MUSCLE FIBER ARRANGEMENT
• EFFECT ON STRENGTH
• The amount of force that a muscle can generate is proportional to the cross-sectional
area of muscle fibers (a.k.a. muscle cells) attaching to its tendon, i.e., the number of
contractile proteins (actin and myosin) pulling on the tendon and contributing to
muscle force.
• pennation design increases the number of muscle fibers (cross sectional area) attached
to the tendon
• since force is a function of cross sectional area - a pennated muscle can generate more
force than a comparable muscle with parallel fibers.

13. • The centre of gravity is the point where the maximum weight of the body
is exerted. It varies in position static animal and during locomotion.
• Normally in a slow moving gait, there will be regular shifting of centre of
gravity from left to the right of the midline resulted in forward movement.
• This will be accompanied by rhythmic sideward movement of the trunk,
head and tail.
• These rhythmic movements of head and tail contribute much to the
maintenance of equilibrium during locomotion.
Center of gravity

14. Center of gravity
• Center of gravity – is cranial to the
intersection of diagonals drawn from
forelimbs to opposite hind limbs. This is
because the cranial part of the body is
heavier.
• Head position – the center of gravity shifts
forward as the head is lowered and
extended forward. It is shifted caudally
when the head is raised because raising the
head also makes the center of gravity more
caudal.
• Head is lowered before kicking – this shifts
the center of gravity forward so that the
body is more stable.

15. EFFECT ON SHORTENING
• In this example, again consider two muscles - one with parallel fibers the other
pennate
• Assume each muscle fiber will contract to 50% of its resting length
• Therefore:
• with parallel-arranged muscle fibers the entire muscle can contract by 50%
• with the pennate arrangement each individual muscle fiber is pulling at an angle,
resulting in reduced overall shortening of the entire muscle belly.

17. Animals are subject to the same physical laws
as inanimate objects.
• An understanding of movement (e.g. motion of the joints and body)
comes through an understanding of the forces acting upon the joint or
the body that result in that movement. Forces can be simplified into
linear and rotational components

18. DEFINITIONS:
• LINEAR FORCE
• Force can be broken down into various vectors.
• Vertical vectors (e.g. the downward forces due to body weight and
the upward forces of the supporting surface)
• Horizontal vectors (e.g. forces exerted to propel forward and
backward forces to brake forward motion)

19. • With adequate force and friction (traction) the body can propel itself forward.
(practical application dictates a need for good traction to allow this forward
motion – whoa to those leading a horse on ice

20. ROTATIONAL FORCE (TORQUE)
• Rotational force = force (F) x distance from fulcrum (d)
• Limb rotation = muscle force (F) x distance from joint (d)
Torque input (muscle generated) = torque output (limb
movement)
Muscles generate forces which when applied to the skeleton
will generate rotation about a joint.

21. MUSCLE ATTACHMENT EFFECTS
• The location of the muscle attachment (e.g. distance from joint) influences the
resultant movement of that joint
• MECHANICAL ADVANTAGE VERSUS VELOCITY ADVANTAGE
• Muscles that attach further from the joint have a mechanical advantage over muscles
attached closer to the joint

22. • In the diagram below if muscles
#1 and #2 were of equal
strength (i.e., can generate the
same force) then muscle #2
could produce a greater
rotational force because its
attachment is at a greater
distance from the joint
(rotational force = muscle force
X distance from joint)

23. • Conversely muscles that attach
close to the point of rotation are
able to produce faster movement
of the lever arm than muscle that
attach farther from the fulcrum.
• In the diagram to the right if
muscle #1 and muscle #2 both
contract 10% during an identical
time period - muscle #1’s
contraction would result in a larger
movement of the lever arm during
that same frame of time than
muscle #2. In other words, muscle
#1 will result in a more rapid
rotation - it has a velocity
advantage

24. • Muscles attaching close to the joint with their velocity
advantage are termed “high gear” muscles and those with a
more distal attachment resulting in a mechanical advantage are
termed “low gear” muscles.
• It may be helpful to consider a similar gear analogy as in a car
or bike.
• At low gears the output force is relatively large – allowing the
vehicle to climb up a steep hill. High gears on the other hand
generates a lot of speed – as would be advantageous in passing
a vehicle.
• Note: the relationship between force and speed is inverse – one
will increase at the same time the other decreases

25. JOINT POSITIONING EFFECTS
• THE BODY’S LEVER SYSTEM
• Unique skeletal features result from
functional adaptations over time.
• In the figure below - the upper
diagram is an example of an animal
that uses it’s front limbs for digging;
the muscles attached to the point of
the elbow (olecranon) are positioned
further from the elbow joint (fulcrum
of movement) thereby generating
large forces for digging.
• The lower diagram with muscles
attaching closer to the elbow joint is
an runner adaptation that can result
in a rapid rotation with muscle
contraction (velocity advantage.

26. APPLICATIONS OF BIOMECHANICS
• Biomechanics is widely used in orthopaedic industry to design orthopedic
implants for joints, dental parts, external fixations and other medical
purposes.
• Biotribology is a very important part of it. It is a study of the performance
and function of biomaterials used for orthopaedic implants.
• It plays a vital role in order to improve the design and produce successful
biomaterials for medical and clinical purposes.
• Used in the treatment and management of lameness.
• Used as Index for draft power.
• Sire index in the selection of draft animals by a breeder.
• Helps in conservation of native germplasm of draft animals.