biomechanics Flashcards
Recognized as the first true biomechanist
• First to study anatomy in the context of mechanics
• Analyzed muscle forces as acting along lines
connecting origins and insertions and studied joint
function
Leonardo da Vinci
• Interested in the strength of bones
• Noted that animals’ with large mass bones increase
in girth
• Theorized adapted to loadbearing
• Suggested that bones are hollow for this affords
maximum strength with minimum weight
Galileo Galilei
Studied walking, running, jumping, and even the piston
action of the heart within a mechanical framework
• Determined
• Position of the center of gravity
• Calculate and measured inspired and expired air
volumes
• Showed that inspiration is muscle-driven and expiration
is due to tissue elasticity
Giovanni Alfonso Borelli
Biomechanics describe the
relationship
between structure and function
Machines function in four ways
Balance multiple forces
2. Enhance force in an attempt to reduce total force
needed to overcome a resistance
3. Enhance range of motion & speed of movement so
that resistance may be moved further or faster than applied force
4. Alter resulting direction of the applied force
3 types of “machines” in producing movement
Levers (most common)
• Torque and length
2. Wheel-axles
• Function essentially as a form of a lever
3. Pulleys
• Single pulleys function to change effective
direction of force application
which class level is most common in human body?
Third-Class Levers
Joint motion is resultant of
- A muscle contraction
• Drawing a distal segment more proximal
• The distal segment will rotate about the
center of the joint
relaxation def.
As the matrix of the segment reaches equilibrium,
or a neutral position, the load necessary to
maintain the length of the segment will decrease
The relative motions of joints surfaces may include
- Gliding
- Rolling
- Spin
- Compress
- Distract
Strength def., what is it dependent on, what does it produce? center of rotation at?
Amount of force needed to contract a muscle
• Dependent on degree of resistance (a.k.a. load)
experienced
• Produces a rotation (torque)
• The center of rotation, fulcrum or axis, is created at the
point of muscle insertion
moment def.,
The force being applied plus the moment arm
• Moment arm = the distance from the center of the
joint to where the contracting muscle is attached
• i.e. (force x distance)
known as the stiffness of the structure
The amount of force necessary to bend an object
rapid stretch vs. slower stretch in terms of resistance
• Rapid stretch will be met with increased resistance
• The faster you squeeze the less water you get out
Biomechanics Principles
• Slower stretch will be met with less resistance
• The slower, longer the squeeze, the more
complete expression of fluid from within the
matrix
slower stretch known as CREEP
types of stress
Force can act upon a structure from various orientations • Tension acts to stretch • Compression • Shearing acts parallel to the surface • Bending acts to fold about an axis • Torsion twists about an axis
mechanical loading can cause
tissue deformation.
load = sum of all stresses
external applied forces
Produced from outside the body & originate from gravity, inertia, or direct contact • Ground reaction forces (GRF) • The force exerted by the ground on a body in contact with the ground
Internal applied forces
• Muscular, joint and skeletal actions of the
body during the execution of a given task
vertical load (internal applied force) def.
Summative weight transmitted
through the kinetic chain to the
ground
• Force that results from the resistance
between surfaces of two objects from
moving upon one another
friction
Only muscles can actively generate
internal force, but tension in tendons,
connective tissues, ligaments, and
joints capsules may generate
passive internal forces
The magnitude of the force applied on the bone known as
strain
The force applied to the insertion or the muscle at the bone results in a
compensatory change in the shape, or deformation, of the bone
balance def.
ability to control equilibrium, either static or dynamic
equilibrium def., static/ dynamic
State of zero acceleration where there is no change in the speed or
direction of the body
• Static equilibrium - body is at rest or completely motionless
• Dynamic equilibrium - all applied & inertial forces acting on the
moving body are in balance, resulting in movement with
unchanging speed or direction
stability def.
The resistance to a • Change in the body's acceleration • Disturbance of the body's equilibrium • To control equilibrium & achieve balance, stability needs to be maximized
field of biomechanics: Description of motion and includes consideration of time, displacement,
velocity, acceleration, and space factors of a system‘s motion
kinematics
field of biomechanics: • Study of forces associated with the motion of a body
kinetics [branch of dynamic]
field of biomec.: Study of systems in motion with acceleration
• A system in acceleration is unbalanced due to unequal forces acting
on the body
dynamic [branch of dynamic]
field of biomech.: • Study of systems that are in a constant state of motion, whether at rest
with no motion or moving at a constant velocity without acceleration
• Statics involves all forces acting on the body being in balance
resulting in the body being in equilibrium
Static
Who defined the concept of “center of gravity”?
a) Andrew Taylor Still
b) Galileo Galilei
c) Giovanni Alfonso Borelli
d) John J. Dougherty
e) Leonardo da Vinci
Giovanni Alfonso Borelli
• Stress through the joint during movement results in a
reciprocal reaction by the structures within that joint (Joint
reaction force) This reaction is in direct response to which
of the following contributing factors:
1. Moments
2. Load
3. Elasticity
4. A & B
5. A, B & C
Moments, load and elasticity!
Which of the following applies a stress to the joint during movement? a) Anatomical joint lever b) Cumulative load c) Joint reaction force d) Tissue deformation
c) Joint reaction force
Deformation can result in loss of:
a) Range of motion
b) Relaxation
c) Resiliency
d) Viscosity
e) All of the above
all of the above
A slow stretch resulting in more complete expression
of fluid from within the matrix is know as:
a) Creep
b) Force
c) Friction
d) Strain
e) Stress
• Three primary joint types
- Fibrous
- Cartilaginous
- Synovial
Consistent repetitive stress can
cause an alteration to the structure
in the form of:
- Failure
• Deformation
• Adaptation
Pain may present as a result on
compensatory mechanism and not original
injury e.g. in
Viscerosomatic Dysfunction
Study of biological systems, human joints
biotribology
2 classifications of biomaterials, examples, types of deformation, how they analyzed
Hard • Bone • Undergo mechanical deformation • May be analyzed with the theory of linear elasticity 2. Soft tissues • Usually undergo large deformations • Cartilage • Tendon • Muscle • Skin
Wolff’s law
• Bone is increased where needed and reabsorbed where it is not • Increased density/hypertrophy related to increase stresses • Decreased – condition of disuse, aging
Cartilage - effect of trauma, abnormal wear? capacity to regenerate? repeated high stresses can lead to??
Trauma or abnormal wear leads to structural disruption of matrix • Loses elasticity therefore increases stiffness • Limited capacity to regenerate or repair • With repeated high stresses can lead to development of degenerative joint disease
ligaments and tendons - effect of increased stress? reduced stres?
Become stronger and stiffer with increased stress • Number and quality of collagen cross-links increase • Physical training • Become weaker and less stiff with a reduction of stress • Loss of collagen • Lower deformation to fail • Immobilization • Aging
SAID principle of skeletal muscle
Specific Adaptation
to Imposed Demands
skeletal muscle - hypertrophy? atrophy?
• S.A.I.D. Principle
• Remodels according to the stresses placed
upon it
• Hypertrophy with physical training results
from increased cross section of fibers
• Atrophy results from disuse or functional
alteration of nerve stimulus to the muscle
Repeated application of stresses can result
in accumulated breakdown of the structure
• This is referred to as
fatigue
Chronic Somatic Dysfunction Characteristics
Fibrosis
- Contracture
- Skin is thin, dry, cool
- Muscles may feel fibrotic
body’s Three sub-segmented “Units”
- Core
- Shoulder Girdle
- Pelvic Girdle
pelvic tilts in lordotic back flat back swayback balanced
lordotic - anterior
flat - posterior
swayback - forward
balanced - neutral
6 things in an OSE
. Gait and station (posture) 2. Anterior and Posterior Spinal Curve Scoliosis 3. TART Findings Tenderness Asymmetry Restriction of motion Tissue texture changes 4. Inspection 5. Percussion 6. Palpation • Note any misalignment, asymmetry, crepitation, defects, tenderness, masses or effusions
