biomechanics (1)
two types of tranlation
curvilinear and rectilinear
equation for angular acceleration
delta angular velocity divided by change in time α units: degrees or radian per s(squared)
equation for angular velocity
delta divided by change in time (ω, sometimes Ω) change in theta over time unit: degree/s, or radians/s
equation for linear velocity
displacement of the body divided by the change of time delta B/T unit: m/s, cm/s
maturation stage
do-360 days aggresive but progressive not able to resist excessive tensile loads in early of this stage decrease in new fibro cartilage
equation for momentum
mass in motion momentum (p) = mass (m) x velocity (v) units: kg m/s
mechanotransduction
mechanical triggers>deformation of cells> communication /signal within the tissues cells>metabolic cellular response
fields of biomechanics
mechanics of fluids mechanics of rigid bodies mechanics of deformable bodies
tissue damping
memory foam
rectilinear
movement of an object the same distance over time
time dependent behaviors of CT's
- creep -stress relaxation response
Viscoelasticity
("when stress-strain relationships change as a function of time")
contact forces acting on the body non contact
- joint and ground, fluid resistance, friction, muscular, elastic, tensile - gravity, electrical
force?
- push or pull - only exist as a result of an interaction
how to collagen elong gate
- reduction of waviness o bundles - small slipping of one fiber relative to the next
What is biomechanics?
-branch of science that studies structure and function of biological systems using principles and methods of physics characterized as mechanics -used to improve human movement -uses math, a and p, physics - kinesiology is part of biomech -involves other biological systems besides just muscular/boney
function of elastin
. Ligaments generally contain more elastin than tendons making them less stiff and just slightly weaker than tendons definition: gives tissues some of their elastic resilience
work equation
= force(magnitude) x S (distance) force can be (F* cos theta) * S units = Nm or Joules
convert radians to degrees convert degree to radians
= r x 57.3 = degrees/57.3
brittle vs ductile
A brittle material is one in which there is little plastic deformation strain prior to failure whereas a ductile material is one that demonstrates a larger amount of plastic deformation as a response to an external load before failing
viscoelastic materials
A material that seems to have both fluid and solid properties . Viscoelasticity is a mechanical behavior in muscle, tendon, cartilage, or ligaments.
Pressure
Amount of force applied per unit area to each body/object Example: "Pressure" = N/cm2
WHY WOULD LIGAMENTS, CAPSULES, & TENDONS BECOME STIFFER AS STRAIN INCREASES?
As the tissue is stretched, more of the fibers are directly aligned to resist the stretch and pack together which results in greater internal resistance as the tissue deforms more and more. Collagen: the greater the density of bonds between the fibers or between the fibers and the matrix, the greater the stiffness
a joint reaction force
Based on Newton's third law, the humerus will push back into the radius.
movment system balance
Optimal function of all contirbuting elements and structures resulting in precise arthrokenimatics and osteokinematics
why stretch slowly
Slower stretching decreases the likelihood of reaching the point of its stress maximum. Hence, there is less likelihood of going into plastic deformation or even failure.
toughness of a tissue
The amount of energy per volume that a material can absorb before rupturing/failing. Toughness measured by considering the total area under the stress strain curve
mechanical stress of human tissues
The internal reaction (resistance) of a tissue to an applied external force. Stress can be thought of as the internal resistance per unit of area to deformation from a force.
mechanical strain of bhuman tissues
The percentage deformation, (shape, length, or width), of a tissue. Normalization: L / Linitial
define resilience
The property of a tissue to absorb energy when it is elastically deformed and then, upon unloading to have this energy vigorously recovered.
define viscosity
The resistance to flow/shear is
Torque (a.k.a. "Moment")
The strength of the rotational forces acting around an axis" math= the force x perpendicular distance from the center of rotation, (axis)
Total Force ?
Total amount of force applied between bodies/objects.
pythagorean theorem
a squared plus b squared = c squared
increase is tensile loading results with
addition of collagen fibrils increase in covalent bonding
curvilinear translation
all parts of an object moved in a curved line
movement system?
all systems that change the positions of any component
rigid body vs non-rigid body
body does not deform with applied pressure vs. deforms with pressure
what is movement?
change in place, position or posture relative to some point within an environment
equation for acceleration
change in velocity divided by change in time deltaV/T units: m/s(squared), cm/s(squared)
human motion
combination of angular and linear
modes of loading
compressive(perpindicular towards), tensile (perpindicular away), shearing(parallel)
(third) newton law of action - reaction
every action there is always opposed an equal reaction forces alway comes in pairs
2 effect of force
external effect - change position of body internal effect - tendency to deform the body
newtons laws of motion
first - law of inertia - resistance of an object to change its current state second - acceleration of an object is direction proportional to the magnitude of the resultant forces acting upon it and inversely proportional to the objects mass A = F/M, force = Mass x acc third -
spatial frames of reference
global and relative frames of reference
stress strain curve
has elastic (beginning of the curve) and non-elastic region (top of the curve when leveling out
why motion capture?
help therapist understand dynamic perspective measurements
fragility
how much a tissue can withstand before failure
types of capture tech
magnetic capture, mechanical (electro-goniometers, videos, infared)
Mechanical advantage (MA)
is the factor by which a mechanism multiplies the force put into it. MA=OUTPUT/INPUT
biomechanics is not a therapy..
it is a science based on tissue stress and musculoskeletal deformities - used to quantify deformities improve diagnosis
kinetics vs kinematics
kinetics - focsued around the forces do or do not do to a body (ie force plates) kinematics - describing mvoement (qualitative/vision observation vs quatitative/numbercal data)
classifications of motion
linear (straight line), angular (rotation), general (combination of both)
characteristics of force
magnitude and direction (together = vector quantity) point of application line of action - forms geimetric orientation cant see force but can see the result of force
consolifdation stage
progressive incerase in tensile forces via AROM and PROM remodeling, union progressively stronger, increase cross links 21-60 days
cellular stage of lig/tendon
protection of tensile loads, clot forms, type III collagen, union is weak and fragile, ruptures with very low tensile stresses day 2-4
hydrated proteins
proteoglycans and glycoproteins these hydrated structures provide a significant role in the material properties of cartilage, bone, tendon, and ligament.
trig functions
soh cah toa
fibroplastic stage
still vulnerable to tensile forces - ideal time to apply low tensile loads such as slow PROM 5-21
equation of power
the rate at which force does work p=dW/dt power = force x speed (velocity)
vision statement for the Pt profession
transform society to optimizes movement to improve the human condition.
equation for eight
weight = mass x acceleration (gravity, 9.8 m/second^2)
