Chapter 4: Linear Force and Motion

law of inertia: if a person is not attached to a moving structure and the structure *suddenly stops*, the person will ________ _______

continue forward

*Newton's Second Law of Motion* is the ___ __ ____________

law of acceleration

*Newton's Third Law of Motion* is the ___ __ _______________

law of action-reaction

______ _____ is force produced by *muscle contraction*

muscle force

inertia must be ________ in order to cause a change in the body's position

overcome

*linear forces* that have the same *point of application* but *opposite directions* are __________ ____ ____ _____

subtracted from each other

a *muscle* can *contract* approximately ___ of its *resting length*

50%

____________ is the *rate* of *change* of *velocity* per unit of *time*

acceleration

______ _____________: -when a *multi-joint muscle* contracts and simultaneous movement occurs at 2 or more joints that it crosses -cannot allow full *ROM* at all the joints it crosses

active insufficiency

*linear forces* that have the same *point of origin* and *same direction* are _____ ________

added together

*active insufficiency* occurs to the _______

agonist

__________ __________ alter their *shapes* in response to *forces* placed upon them

anatomical structures

*passive insufficiency* occurs to the __________

antagonist

the *length* of the fibers within a *muscle* is a function of the ____________ of that *muscle* rather than of the *muscle's total length*

architecture

_______ _____ causes *asymmetric loading*

bending force

_______ _____ produces *tension* on one side of the *longitudinal axis* and *compression* on the other side

bending force

a _______ ______ is what usually causes a long bone *fracture*

bending force

___________ _____ pushes 2 surfaces *closer together*

compressive force

__________ ______: -2 or more forces that meet at the *same point* but in *different directions* -do not lie along the same *line of action*, but *form* an *angle* with each other

concurrent forces

a *balanced force* keeps an object *moving* at a ________ ________

constant velocity (Newton's 1st Law of Motion)

the *force generated* by a muscle depends on the number of _____ _______ attached

cross bridges

during a contraction, the faster the *actin* and *myosin* filaments slide past each other, fewer _____ _____ formed, less *force* is produced

cross links

as the *mass* of an object is *increased* the *acceleration* of the object is _________

decreased

forces cause objects to ______ __ ____

deform or move

*active insufficiency* involves *sufficient shortening* ability in the _______ _________

desired direction

force: _________ is the *path* a *force travels*

direction

when *forces* are *balanced*, there is *no change* in the _________ __ ______ of an *object*

direction or motion

*law of acceleration*: the *acceleration* of an object is ________ ____________ to the *net force* acting on it

directly proportional

there is a ________ ____________ relationship between number of *motor units stimulated* and *muscle force generated*

directly proportional

on the *opposite side* of a joint, the *antagonist muscle* must have *adequate* ______________ to allow the joint to move through its full *range of motion*

distensibility

an *anatomical structure's* tendency to return to its *original* shape after an applied force is removed is due to the _______ __________ of the *tissue*

elastic properties

__________ is the ability of a structure to *return* to its *original shape*

elasticity

_______ is a *protein* in connective tissue that allows tissue to return to form after *stretching* or *twisting*

elastin

usually, a *muscle* has *sufficient excursion* to allow the joint it crosses to move through its ______ _____ __ ______

entire range of motion

*law of action-reaction*: for every *action*, there is a(n) _____ ___ ________ ________

equal and opposite reaction (equilibrium)

the *resultant magnitude* of *concurrent forces* is not *halfway* between the *forces* unless the *forces* are of _____ _________

equal magnitude

the *resultant magnitude* of *concurrent forces* is not the *sum* of the *forces* unless the *forces* are of _____ _________

equal magnitude

when *external* and *internal forces* are *balanced*, the object is in ___________

equilibrium

the *3rd* law of motion is concerned with how objects push on each other and ________ ________ when they *interact*

exchange momentum

________ ______ are *forces* that are *outside* the body

external forces

*force* can be classified as either ________ __ ________

external or internal

a *multi-joint muscle* is most *effective* when *one joint* is _____, while *movement* occurs at the *other joint*

fixed

a push or pull is a _____

force

________ is between *contact surfaces*; a *force* that *opposes movement* of one object over another

friction

________ is the *resistance* to *movement* when 2 structures are in *contact* with each other

friction

movement occurs because of *differences* in ________ ___ ____ between the objects

friction and mass

the *ability* of a *muscle* to move a *joint* through its ____ _____ __ ______ depends on *muscle fiber length* and *moment arm of the muscle*

full range of motion

by *positioning* the *patient's limb* so that the *contracting muscles* are *functioning* in the *stretched position*, the *clinician* enhances the *muscle's* ability to ________ _______

generate tension

*Sir Isaac Newton* identified and described the laws that ______ ______

govern motion

_____________ _____ tends to *pull* the body *downwards*

gravitational force

provided that everything is *equal*, it will require a _______ _____ to move an object of *greater mass*

greater force

______ ________ _____ is the *forces* that act on the body as a result of *interaction* with the *ground*

ground reaction force

*sarcomeres* __ ________ are side by side, like plates stacked on top of each other

in parallel

*sarcomeres* __ ______ are end to end, like plates next to each other

in series

both *active and passive insufficiency* result in __________ ________ of *some* or *all* of the *joints* crossed by the *muscles involved*

incomplete movement

as the *force acting* upon an object is *increased*, the *acceleration* of the object is _________

increased

_______ is the *resistance* of any body to *change* its *current state* of *rest* or *motion*

inertia

________ ______ are generated by *body tissues*

internal forces

there is a(n) _______ ____________ between the *speed* of *contraction* and amount of *force* the muscle can generate concentrically

inverse relationship

*law of acceleration*: the *acceleration* of an object is _________ ____________ to its *mass*

inversely proportional

the amount of *torque* required to create *movement* at a *joint* varies with the _____ _____

joint angle

the *muscle's ability* to produce force varies with the _____ ________

joint position

_____ ________ _____ is the force between the *articular surfaces* of a *joint*

joint reaction force

*Newton's First Law of Motion* is the ___ __ _______

law of inertia

the ___ __ _______ helps us to better understand why objects *move, change direction, slow down, and stop*

law of inertia

in a __________ position, *too little* overlap occurs, reducing the number of *cross-bridge* connections that can occur

lengthened

________ _____ is force produced by a *ligament* when *stretched*

ligament force

force: a ____ __ ___________ is a *line* passing through the *point of application* in the direction of the *applied force*

line of application

______ ______: -2 or more forces acting along the *same line* -the *point of application* lies in a *straight line*

linear forces

muscle contractions create ______ ______

linear forces

*parallel muscles* tend to be ______ than *pennate muscle fibers*

longer

*tensile forces* cause *joint structures* to become ______ ___ ________

longer and narrower

*parallel muscles* are located in positions requiring ______ _________ ____ ____ _____

longer movements with less power

force: _________ is the *size* or *amount* of *force exerted*

magnitude

*resultant force* depends on the _________ ___ _____ of each *force*

magnitude and angle

____ is the amount of *matter* a body contains

mass

force = ____ _ ____________

mass x acceleration

______ is anything that has *mass* and takes up *space*

matter

*pennate muscle fibers* generate ____ _____ than *parallel muscles*

more force

a _____ _____ ______ produces *movement* at more than one *joint*

multi joint muscle

________ ______ may act on a structure *simultaneously*

multiple forces

______ _________: -the *distance* a muscle can *shorten* -the *difference* between a *muscle's maximum elongation* and *maximum shortening*

muscle excursion

the ______ ______ _______ ____________ states that the amount of *force* a muscle generates depends on the length of the muscle at the *beginning* of the contraction

muscle length tension relationship

the *direction* of a *muscular force* is the *direction* of the ______ ____ __ ____

muscle line of pull

a ______ ______ ___ is the *perpendicular distance* between the *axis* of a *joint* and the *muscle's line of force*

muscle moment arm

______ ________ is the *maximal* amount of *tension* or *force* a *muscle* or *muscle group* can generate in one *maximal* effort (1RM) at a *specific velocity*

muscle strength

_______ produce force

muscles

*compressive forces* cause *joint structures* to become ________ ___ _____

narrower and wider

the _______ ______ controls: -which and how many *motor units* are *stimulated* -the rate motor units are *fired*

nervous system

*passive insufficiency* involves *insufficient passive lengthening/stretching* in the ________ _________

opposite direction

_______ ___________ allows for *optimal overlap* such that the *optimal cross-bridge connections* can occur between *actin* and *myosin*

optimal positioning

a body at rest remains at rest, and body in motion remains in motion, unless acted upon by an _______ _____

outside force

________ ______ are 2 or more forces that: -act *parallel* to each other -act in the the *same plane* -act at *2 different points* -can act in the *same or different directions*

parallel forces

most *muscles* of the body are ________ _______

parallel muscles

_______ _____________: -the *inability* of a *multi-joint muscle* to *elongate sufficiently* to allow full *ROM* at *both joints* when movement occurs at *both joints simultaneously* -the *full elongation* of a *2 joint muscle (antagonist)* prevents the *full shortening* of the *opposing muscle (agonist)*

passive insufficiency

in ________ ______ ______, *fascicles* form an *angle* with the *tendon*

pennate muscle fibers

*pennate muscle fibers* contain more *muscle fibers* per _____________ _____ _________ ____ than *parallel muscles*

physiological cross sectional area

the greater the _____________ _____ _________ ____ of the *muscle*, the greater the *force* of *contraction*

physiological cross sectional area

force: a _____ __ ___________ is the the exact *location* on an object where a *force* is *applied*

point of application

repeated *shearing forces* can cause ________ _____

pressure sores

*parallel muscles* have a *greater potential* for producing more _____ __ ______

range of motion

*pennate muscle fibers* produce less _____ __ ______

range of motion

a *muscle moment arm* changes throughout the _____ __ ______

range of motion

*weakness* is a common *impairment* in *individuals* participating in ______________

rehabilitation

if *stabilization* does not occur at one of the *joints* crossed by the *muscle*, the *muscle* will shorten through its *full excursion* but the *ROM* in the various *joints* _______ __________

remains incomplete

__________, such as *water* or *wind*

resistance

when *forces* are *not balanced*, there is a change in an object's ____ ______ __ _________

rest motion or direction

when *external* and *internal forces* are *balanced*, there is a *change* in an object's ____ __ ______

rest or motion

_________ _____ is the *overall effect* of 2 or more forces acting on a *body or segment*

resultant force

when *linear forces* are associated with an *articulation*, a ______ ______ will occur

rotary motion

*resistance training* can increase the number of __________ __ ________

sarcomeres in parallel

________ _____ acts *parallel* to the *surface area*

shearing force

a *multi-joint muscle* cannot move all of the related *joints simultaneously* through complete *ROM* because the muscle would have to _______ ____ ____ ________

shorten more than possible

in a _________ position, *too much* overlap occurs, resulting in *fewer* available *cross-bridge* sites

shortened

*parallel muscles* have a *greater potential* for __________

shortening

*muscles* with _______ ______ ____ are capable of producing greater *ROM*

shorter moment arms

an *OT* must consider the *law of action-reaction* when __________ ________

supporting patients

_______ _____ pulls 2 surfaces *apart*

tensile force

_______ _____ tends to *elongate* the soft tissue structures in the *direction* of the *applied forces*

tensile force

_______ _____ tends to cause *damage* to the *ligaments* and/or *tendons*

tensile force

*tissue damage* occurs when the *applied force* exceed the ________ __________

tissue's elasticity

______ is the tendency of a *force* to produce *rotation* around an *axis*

torque

_________ _____ causes a *rotation* or *twisting* action

torsional force

_________ _____ occurs when a structure is *twisted* about its *longitudinal axis* while one end of the structure is *fixed*

torsional force

*unbalanced forces* _____ ___________

upset equilibrium

when *movement* is occurring at *both joints* , only ____ ____________ can occur

weak contractions