OCC 501 Occupational Therapy Exam 1: Biomechanics Mastery – Kinematics, Kinetics, and Therapeutic Movement Analysis | 69 Expert-Curated Q&A with Detailed Rationales, Clinical Applications, and Functional Outcome Strategies

Line of Gravity (LOG)

Imaginary vertical line through head, torso, COG & ground

direction of gravity on body

force of direction

Center of Gravity (COG)

point in the upright body where the mass is evenly distributed

anterior to S2

Base of Support (BOS)

region bounded by body parts in contact with a support surface

exerts a counterforce again bodies applied force

larger BOS= more stability

Transverse Plane + movements in plane

Divides body into top & bottom

rotational movements- spinning in ice skating

Frontal Plane + movements in plane

Divides body into front and back

abduction/adduction movements- jumping jacks, arm abduction

Saggital plane + movements in plane

Divides body into left and right

flexion & extension movements- throwing ball, squat

Vertical axis

divides body into top and bottom

Mediolateral axis

divides body into left and right

Anterior Posterior Axis

divides body into front and back

posture

position of your body parts in relation to each other

postural control

Person's ability to maintain stability of the body and body segments in response to forces that threaten to disturb the body's equilibrium

anticipatory posture

set of postural strategies that prepare an individual for different types of voluntary movement

can be learned or automatic

feedforward

CNS sends signals ahead of time regarding muscles and force required for movement (anticipatory)

compensatory

strategies used in response to external force causing instability or perturbation

feedback

CNS responses during or after movement, responds to postural disturbances (compensatory

orientation

maintain appropriate relationships between body, body segments and environment

stability

ability to maintains one's COG within the base of support

depends on task and environment

purposes of posture (4)

1. control bodies orientation in space

2. stabilize the head with respect to vertical plane

3. maintain body's COG over its BOS

4. facilitate vitals & organ function

Components of posture (4)

1. Base of support

2. line of gravity

3. center of gravity

4. pelvic tilt

anterior pelvic tilt

decreases angle of hip joint

ASIS moves forward

pubic symphysis moves back

"pouring water out of bowl"

posterior pelvic tilt

ASIS moves backwards

hamstrings tighten

"scooping up"

lateral pelvic tilt

sideways movement

pelvis shifts up on one side

Kyphosis-Lordosis

kyphosis- rounding of spine

lordosis- curving in of spine

kyphosis in thoracic spine

lordosis in lumbar spine

anterior pelvic tilt

exaggerated form of normal spinal curve

Sway Back

kyphosis in thoracic spine

lumbar spine begins to flatten out

posterior pelvic tilt

leg hyperextension

Flat Back

entire spine begins to flatten

hips are extended

posterior pelvic tilt

Body Mechanics

the art of distributing work over several sets of muscles and using the most efficient ones

Purposes of body mechanics (3)

1. Conserve energy

2. Preserve equilibrium

3. Minimize forces on joints

statics

aspects of non-moving joints

dynamics

aspects of moving system

kinetics

studies forces that create motion

gravity, friction, pressure

kinematics

analyzes mechanical elements of movement

time, space, mass

force

Any influence that tends to accelerate an object; a push or pull; measured in newtons. A vector quantity.

inertia

objects resistance to change in a state of rest or motion

torque

a force with a twist, force that involves rotation of an object around an axis

Newton's 1st Law

Law of Inertia

An object in motion tends to stay in motion. An object at rest tends to stay at rest

Newton's 2nd Law

Law of Acceleration

the acceleration of an object will be directly proportional to the force and inversely proportional to the mass of the object

Newton's 3rd Law

Law of Action- Reaction

for every action, there will be an equal and opposite reaction

linear forces

occurs when all forces occur along the same line of action

can act in same or opposite direction

can create tension or compression

parallel forces

act on the same plane and are aligned with each other

can move in the same or opposite direction

concurrent forces

when 2 or more forces connect to a common point, but pull in divergent directions

ex. tug of war between two teams

Lumbar disc slip

occurs due to pelvic tilts

with ant. pelvic tilt, will create pressure posteriorly, spinal parts will come together, pushing disc forward and creating an anterior disc bulge

post. is same principles, will create posterior disc bulge

Principles of good body mechanics

1. maintain proper pelvic tilt for position and task

2. maintain good alignment of head and neck

3. maintain stable BOS- feet shoulder-width apart

4. change positions frequently

5. bend from knees & hips together

6. keep hips & shoulders parallel

7. push before pulling, pull before lifting

8. use proper work heights: elbow height when seated, 2-4 in below elbow when standing

9. when lifting or carrying a heavy object, tighten abdominals

10. keep objects close to work surface to body

11. pivot instead of twisting

momentum

property of a moving body which determines length of time to ring it to rest when under action of constant force or motion

moving WITH gravity

if we are standing, reach down to do something

moving AGAINST gravity

if we are reaching up, moving away from the earth

moving ACROSS gravity

movement across horizontal plane, gravity isn't helping or resisting us

torque

force that produces rotation of an object about an axis

can be internal or external

critical factors for torque (2)

1. amount of force exerted

2. distance from the force to the axis (moment arm)

torque equation

torque = force x moment arm

stabilizing force

when arm is fully extended

exertion directed back at joint; stabilizing muscles and pulling them together

angular force

90° flexion, muscles are pulling away and generating the most torque

dislocating force

Past 90 degrees, force is directed away from the joint and moving joints away from each other.

lever

rigid structure that moves around fixed point (axis) to gain mechanic advantage

effort

force you are putting in work

effort arm

moment arm of effort, distance

resistance

the load that is moved by the lever

resistance arm

the span between the resistance and axis

mechanical advantage

effectiveness of the machine

MA= EA/RA

the longer either arm or the more force of either arm will increase the torque

first class levers

axis is in between effort and resistance

variable distance of effort and resistance arm, situational based

poor range of motion and speed

small exertion used to mobilize larger load

can manage heavier loads with less effort

ex. seesaw

second class lever

resistance between the axis and the effort

effort arm is always longer than resistance

less range of motion & speed

due to longer effort arm, requires less effort to move larger amounts of weight

always > 1 (effort longer than resistance)

ex. wheelbarrow

third class lever

effort is between resistance and axis

resistance arm is always longer than effort

most common in body

is able to move loads with shorter distances

always < 1 (resistance longer than effort)

ex. broom, tweezers

Pulley systems

changes direction of pull or force

can increase or decrease the magnitude of force

simple fixed pulley- only changes direction, no mechanical advantage

moveable pulley- transmits power to resistor, assists motion; working using moveable pulleys

agonist

primary mover in an action

antagonist

muscle opposing movement

antagonist

muscles working in opposition of each other

isometric contraction

muscle contracts but there is no change in length

concentric contraction

muscle shortens during contraction

eccentric contraction

muscle lengthens during contraction

isotonic contraction

muscle changes length; includes eccentric and concentric contraction