Basic Biomechanics ch.2 Flashcards by shawna shinody

function of the musculoskeletal system is described by a branch of physics termed ?

mechanics

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structure

anatomy

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function

physiology

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mechanics

study of forces & the effect of application of forces on stability & motion of the body

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2 main areas of dynamics

static
dynamic

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factors associated w/ non-moving systems

tasks; sitting, laying down

static

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2 factors associated w/ moving systems: kinetics & kinematics

ex; walking, rolling in bed

dynamics

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forces producing stabilization or movement in a system

kinetics

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motion created by forces & incorporates time, space, and mass

ex: running & walking

kinematics

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kinematics is divided into 2 types

osteokinematics
arthrokinematics

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quantity describing only magnitude

speed (M/H), length, area, vol, & mass

scalar

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the amount/aggregate of matter in an object
(human body)

mass

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magnitude & direction. common measures force, velocity, and acceleration

vector

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indication of amount of measurement

magnitude

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the direction in which the magnitude is applied
(flexion/extension)

direction

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amount & direction of push/pull applied to objects or body segments

force

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push creates?

compression

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pull creates?

traction (pulling apart)

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2 types of forces?

internal
external

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mutual attraction bt. earth & an object?

gravity

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external forces include?

gravity
external pressure (weights or friction)

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internal forces include?

muscle contraction
ligamentous restrained
& bony support

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the force exerted on an object/person as a result of gravity

gravitational force

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result of gravitational force & mass of an object always pushing down

weight

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the upwards force supporting surface exerts on an object (person) when a person pushes down on it

ground reaction - no ground reaction = fall into eternity

force bt. 2 surfaces that increase resistance to motion of 1 surface across another increased by compression (rubbing) decreased by traction

friction

types of different configurations of force

linear - 2+ forces act along the same line parallel - same plane & in the same/opposite direction concurrent - push/pull in different directions - goes diagonally

occurs when 2 or + forces act in different directions, producing a rotation. ex: scapula

force couple

sum of the magnitudes & directions of each individual force vector ex: deltoid muscles

resultant force

5 mechanical effects of force application to body

traction compression shear bending rotation (twisting)

joint surfaces pull apart

traction why? reduce compression to decrease pain. too much = dislocation

joint surfaces push closer together? ex: running, squats, jumping

compression why? stability and strength. too much = cartilage problems & compression fx

gliding motion of joint surfaces parallel to 1 another ex: knee extension

shear Why? reduce pain alleviate movement. too much = tissue strain/rupture

2 opposing forces twisting within an object in opposite directions ex: ACL injuries

torsion excessive torsional forces = ligament tear or spiral fx of bone.

force is not applied at the central axis. causes compression to one side and traction to the opposite side ex: spinal trunk bending/flexion

bending

tendency of a force to produce rotation about an axis

torque

is muscle more efficient at 90 degrees for creating rotary motion?

yes! it is less efficient if jt angle is near the beginning or end of the jt's ROM

the perpendicular distance bt. the line of application of force & the axis of motion

moment arm

newtons 1st law object stays at rest or in motion unless acted upon by an external force

law of inertia

amount of torque generated depends on

amount of force applied distance from axis that force is applied ex; pt seated, my hand @ the ankle vs knee as resistance

what is the angle at which force is applied ?

the angle of application of force -force can be applied perpendicular = torque or at an angle to the limb

lower extremity in swinging phase of gait force required to start: hip flexors force required to stop leg: hamstrings

newtons 1st law, law of inertia

newtons 2nd law: acceleration depends on the strength of the force applied to the object

law of acceleration

adding ankle weights for a greater muscle force needed to start & stop a leg swing

newtons 2nd law, law of acceleration

acceleration is inversely proportional to the ___ of an object and directly proportional to the amount of ___

mass, force

trampoline, the harder you jump the higher you rebound

newtons 3rd law, law of action-reaction

newtons 3rd law: force applied creates an equal & opposite reaction

law of action-reaction

sum of the mass of all body segments is located

Center of mass (COM)

when the sum of all forces acting on an object = 0

equilibrium - no motion occurs - also dependent on COM, COG, & BOS of the object

the area encompassed by the body's contact w the supporting surface

Bas of supports (BOS)

point at which gravity acts on the COM slightly anterior to S2

Center of gravity (COG)

imaginary vertical line passing though the COG to the center of the earth

Line of gravity (LOG)

types of motion

linear motions (translatory) curvilinear motion angular motion (rotary)

all parts of an object move the same distance at the same time ex: kid sledding down a hill

linear motion

motion occurring in a curved path, not circular ex: skier takes curved path coming down a slope

curvilinear motion

movement of an object around a fixed point (axis) ex: knee joint for flex/extension

angular motion

types of simple machines

levers pully inclined planes

axes

joint

levers

bone

force

muscle & weights

rigid "plank" rotating about a fulcrum with application of force

lever

what class lever is the skull on the 1st vertebrae?

1st class force = ant/post muscle axes = skull and vertebrae resistance = weight of head

what class lever is a person rising on their tippytoes?

2nd class lever favor force axis = metatarsophalangeal (MTP) foot resistance = body weight pushing down force = plantar flexor muscles

what class lever is the biceps brachii muscle flexing the elbow ?

3rd class lever axis = elbow jt force = biceps brachii muscle resistance = weight of arm/forearm

whats the most common lever in the body?

3rd class level - favor distance

force is gravity

2nd lever

what lever results in resistance is gravity, force is a muscle

3rd

a grooved wheel that turns about an axis w a rope/cable tie ridding in the groove provides attachment for an applied force & a load

pulley - used to change the direction of a force or change the magnitude the "wheel" is the bone "rope" is tendon or muscles

2 types of pulley's?

fixed pully moveable pully

a single pulley attached to a fixed point, creating a 1st class lever configuration

fixed pully ex: lateral malleolus & fibularis longus or patella w the quad or overhead and wall pulley in clinical setting

T/F: there is no moveable pully in the human body

TRUE

combines a fixed pully to change direction & a moving pulley to change magnitude of force applied to lift a load

movable pully

inclined ramp?

a flat surface that slants from one level to another

federal requirement for slope of wheelchair ramp?

1inch rise & 1foot run