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
