Biomechanics is the study of biological systems using mechanical principles. It draws from biology and physics to describe the movement of living organisms. Biomechanics aids in understanding human movement through analyzing kinetics, which examines causes of motion like forces and torques, and kinematics, which describes motion in terms of displacement, velocity and acceleration. Proper biomechanical analysis is important for understanding injuries and designing rehabilitation.
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Biomechanics concepts
1. BIOMECHANICS
CONCEPTS
BIOMECHANICS
Study of Biological Systems by
Means of Mechanical Principles
father of Mechanics
Sir Isaac Newton
2. Biology Physics
Skeletal Muscular Nervous Mechanics
system system system
Kinetics Kinematics
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3. HUMAN MOVEMENT ANALYSIS
BIOMECHANICS KINESIOLOGY
KINETICS KINEMATICS FUNCTIONAL
Linear Angular Linear Angular
Position Position
Velocity Velocity Force Torque
Acceleration Acceleration
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4. Basic types of Motion
Linear
Rectilinear
Curvilinear
Angular or rotational
Combined or general
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5. Human Analysis
Internal: mechanical factors
creating and controlling
movement inside the body
External: factors affecting
motion from outside the body
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6. Kinematics
Describes motion
Time
Position
Displacement
Velocity
Acceleration
Vectors
Angular and linear quantities
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8. Kinetics
Explains causes of motion Axis
Mass
amount of matter (kg)
Inertia: resistance to being moved
Moment of Inertia (rotation) I = m·r2
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9. Kinetics
Force: push or pull that tends to
produce acceleration
Important factor in injuries
Vector
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10. Kinetics
Idealized force vector
Force couple system
F
F’ F M=Fd
d d d
= =
F F
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11. Kinetics: Force
Force & Injury factors
Magnitude
Location
Direction
Duration
Frequency
Variability
Rate
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12. Kinetics: Force System
Linear
Parallel
Concurrent
General
Force Couple
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13. Center of Mass (COm) or
Gravity (COG)
It is an imaginary point where
there is intersection of all 3
cardinal plane.
Imaginary point where all the
mass of the body or system is
concentrated
Point where the body’s mass is
equally distributed
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14. Pressure
P = F/A
Units (Pa = N m2)
In the human body also
called stress
Important predisposing
factor for injuries
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15. Moments of Force
(Torque)
Effect of a force that tends
to cause rotation about an
axis
M = F ·d (Nm)
If F and d are
Force through axis
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16. Moments of Force
(Torque)
Force components
Rotation
Stabilizing or destabilizing
component
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17. Moments of Force
(Torque)
Net Joint Moment
Sum of the moments acting
about an axis
Human: represent the
muscular activity at a joint
Concentric action
Eccentric action
Isometric
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18. Moments of Force
(Torque)
Large moments tends to produce injuries on the
musculo-skeletal system
Structural deviation leads to different MA’s
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20. 1st Law of Motion
A body a rest or in a
uniform (linear or angular)
motion will tend to remain
at rest or in motion unless
acted by an external force
or torque
Whiplash injuries
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21. 2nd Law of Motion
A force or torque acting on a body will produce an
acceleration proportional to the force or torque
F = m ·a or T= I ·
F
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22. 3rd Law of Motion
For every action there is an
equal and opposite reaction
(torque and/or force)
Contact forces: GRF, other
players etc.
GRF
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23. Equilibrium
Sum of forces and the sum of
moments must equal zero
F=0
M=0
Dynamic Equilibrium
Must follow equations of motions
F=mxa
T=Ix
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24. Work & Power
Mechanical Work
W= F ·d (Joules)
W= F ·d·cos ( )
Power: rate of work
d
P = W/ t (Watts)
W W
P = F ·v
P = F ·(d/t)
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25. Mechanical Energy
Capacity or ability to
do work
Accounts for most
severe injuries
Classified into
Kinetic (motion)
Potential (position or
deformation)
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26. Kinetic Energy
Body’s motion
Linear or Angular
KE=.5·m·v2
KE =.5 ·I· 2
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27. Potential Energy
Gravitational: potential to
perform work due to the
height of the body
Ep= m·g·h
Strain: energy stored due to
deformation
Es= .5·k·x2
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28. Total Mechanical Energy
Body segment’s: rigid (nodeformable), no strain
energy in the system
TME = Sum of KE, KE , PE
TME = (.5·m ·v2)+(.5 ·I · 2)+(m ·g ·h )
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29. Momentum
P
Quantity of motion
p=m ·v (linear)
Conservation of Momentum
Transfer of Momentum
Injury may result when momentum
transferred exceeds the tolerance
of the tissue
Impulse = Momentum
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30. Angular Momentum
Quantity of angular
motion
H=I · (angular)
Conservation of angular
momentum
Transfer of angular
momentum
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31. Collisions
Large impact forces due to short impact time
Elastic deformation
Plastic deformation (permanent change)
Elasticity: ability to return to original shape
Elastoplastic collisions
Some permanent deformation
Transfer and loss of energy & velocity
Coefficient of restitution
e=Rvpost/Rvpre
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32. Friction
Resistance between two bodies
trying to slide
Imperfection of the surfaces
Microscopic irregularities -
asperities
Static friction
f< s·N
f
Kinetic
f=µk·N N
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