SB - 1-3 Flashcards
Biomechanics
The application of mechanical laws to living structures… Specifically to the locomotor system of the human body
Considers the physics of movement of a body in space
Kinematics
The branch of mechanics that deals with the geometry of the motion of objects, including displacement, velocity and acceleration, without taking into account the forces that produce motion
Kinetics
The study of the relationships between the force system acting on a body and the changes it produces in body of motion
What are the three body/cardinal planes?
Sagittal
Coronal
Transverse
Sagittal body plane
Anterior to posterior
The vertical plane that divides the body into right and left
Flexion and extension occur in this plane
Coronal body plane
Frontal
Vertical plane that divides the body into front and back
Lateral or side to side motion
Transverse body plane
Horizontal plane that divides the body into upper and lower components
Rotation occurs in this plane
Cartesian coordinate system/axis of motion
3 axis?
X
Y
Z
X axis
Runs side to side
Flexion and extension occur around this axis, but in the sagittal plane
Y axis
Runs up and down
Rotation occurs around this axis, but in the transverse plane
Z axis
Runs front to back
Lateral bending occurs around this axis, but in the coronal plane
Center of mass (CoM)
Theoretical construct that is defined as a point about which the bodies mass is equally distributed
Center of mass (CoM) =
Center of gravity (CoG)
Center of Gravity (CoG)
The hypothetical point at which all the mass of the object or segment appear to be concentrated
Where does the center of mass lie in anatomical position?
On average, it depends on the proportions
Lies anterior to the second sacral tubercle
Location of CoM is __________
VARIABLE
depends on the body position
- lowering the CoM above the base of support increases the stability
Base of Support (BoS)
The area which supports the mass above
Translational Motion
Linear displacement
Each point on a segment moves in a straight line through the same distance, at the same time, through parallel paths.
Ex. Push or pull a glass
Rotational motion
Angular displacement
Each point on a segment moves in a curved path around a fixed axis through the same angle, at the same time, at a constant distance from the axis
Lift water glass at elbow
General Motion
A combo of transitional and rotational motion
Involves instantaneous center of rotation (ICoR) or instantaneous axis of rotation (IAoR)
In the body, most joint rotation occur across 3 planes (are 3 dimensional) and involve helical or screw axis type motion
Line of support
Falls between the legs when standing in anatomical position
Must fall within the base of support to remain stable
Newton’s First law
law of inertia; an object will remain at rest or in uniform motion unless acted on by an unbalanced force
static equilibrium
remains motionless when acted on by forces
dynamic equilibrium
remains in constant motion when acted on by forces (rare in the human body)
Newton’s 2nd law
law of acceleration - the acceleration of an object is proportional to the net forces acting on it and inversely proportional to its mass; greater the mass, the more force it takes to move it; nfl lineman = more mass, more force to move it
Newton’s 3rd law
the law of reaction - for every action there is an equal and opposite reaction; the force you apply, a part will come back into your body
linear force system
two or more forces act on the same object, in the same plane, and in the same line. lines of force run parallel to each other. not very common in the body
concurrent force system
the lines of force are at angles to each other and converge at some point either internal or external to the object. any two forces can be composed into a single resultant force
tissue slack and line of drive may be used, but the actual procedure is performed using the
resultant vector
resultant vector
putting all lines of drive and tissue slack together
distraction forces
a net force that mvoes an object (bony segment) away from an adjacent object (bony segment). pulling 2 objects away from each other
tensile forces
forces that create opposite pulls on an object; opposite forces are necessary to create tension (ligaments and joint capsules) end feel. create tensile forces by distraction
accessory motions
small, involuntary movements of a joint that are necessary to produce its gross movement
coupled motion
groups of motions that are necessary to produce the gross motion
body works on a ____ system; increases the
pulley; mechanical advantage
gravitational forces
the result of gravity on an object
contact forces
reaction forces resulting from the push of one object against another; aka joint reaction forces when it involves two contiguous joint surfaces. 2 objects touching each other (knee joint while laying down)
compression forces
two forces that cause joint reaction forces. knee while standing: compression in the joint
close packed position
clase packing a joint - the rotation of 1 segment of a joint relative to the adjacent segment (twisting), drawing the adjacent articular surces into contact (compression). This is caused by creating tension in the caspuloligamentous structure. this is when the joint is at its most stable
spondylolisthesis
L5 slips forward. grade 5: completely off base of the sacrum
when there is trauma, ___ rushes to help stabilize and reinforce resulting in ___ ___
calcium; bone spurs
shear forces
any forces that are parallel to contacting surfaces, attempting to move one object on another. ex: hands together
friction forces
potentially exist whenever there is contact force and is opposite the direction of the shear force.
must have a ____ force to produce a friction force
shear
the friction force is trying to ___ glide
resist
____ is the opposite of shear forces
friction
shear and friction forces play a significant role in
vertebrae
torque/moment force
the strenth of rotation produced in an object when an isolated force does not pass through the CoM. A combo of rotatory and translatory motion. there is always torque in the body.
parallel force systems
two or more forces applied to the same object that are parallel to each other
torsional moment
occurs when torque forces produce a rotation of a segment around its long axis. Most muscles produce torques/moments around two or more axes because they attach at the periphery of the bones
torsional forces create a “______” motion between two objects
twisting
total muscle forces
the resultant vector of the concurrent force system is produced by the fibers of a muscle contracting. vector is from the point of application or muscle attachment and parallel to the muscle fibers and tend. the direction of pull is always towards the center of the muscle.
every muscle pulls on each of its attachments every time it exerts a ____
force
muscle pulls along a
tendon
anatomical pulleys
bones that alter the direction of pull of a muscle. They deflect the action line of a muscle away from the joint axis, thus increasing the moment arm (MA) and torque produced by a muscle force
MA of a force and torque are greatest when at ___ degrees to the segment and minimal at ___ degrees
90; 0
first class lever
rare in the body; the axis lies between the effort force and the resistance force
second class lever
the resistance force lies between the axis and the effort force
eccentric contraction
2nd class lever; muscle lengthening as it contracts
concentric contraction
3rd class lever; muscle shortens as it contracts
3rd class lever
the effort force lies between the axis and the resistance force
when the muscle is the effort force=
concentric contraction
when the muscle is resistant force=
eccentric contraction
when effort force=resistance force (no net torque) =
isometric contraction
weight ___ mass (on earth)
equals
weight = / mass (on the moon)
1/6
weight = ___ in space
0
weight = ____ x ___ ___ ___
mass
force of gravity
force = ___ x _____
acceleration
