Work/Power/Energy

force times displacement

what is work?

N*m or Joule

units of work (2)

true

true/false: have to move a distance (displacement) for there to be work done

force, length change

work of muscle = muscle ________________ x muscle __________________

concentric

___________________ contractions are positive

eccentric

_____________________ contractions are negative

positive (work)

does a concentric contraction indicate positive or negative work?

negative (work)

does an eccentric contraction indicate positive or negative work?

recruitment, synchronization

2 methods of increasing strength with regards to motor units

true

true/false: you have to use weight/external load to improve strength

positive

in the flexion portion of a biceps curl, the biceps are doing ________________ work on the load

negative

in the extension portion of a biceps curl, the biceps are doing __________________ work on the load

shortening

in concentric contractions, the muscle is doing what?

lengthening

in eccentric contractions, the muscle is doing what?

biceps curl (biceps), calf raises (triceps surae), lat pulldown (lats)

3 examples of positive/concentric work

lateral raises (deltoids), lowering from shoulder press (deltoids), extending from biceps curl (triceps)

3 examples of negative/eccentric work

agonists and antagonists

what do you have to keep in mind when figuring out if exercises are concentric or eccentric?

eccentric, better muscle activation due to gravity

are eccentric or concentric exercises better? why?

length-tension relationship

the relationship of muscle length to its ability to generate strong contractions

initial contact: force increases rapidly without a change in length, then length increases as force decreases

describe the length-tension relationship for the gastroc during the support phase of running

concentrically, positive

the quadriceps muscles are active _____________________ when one ascends stairs and lifts the weight of the body, which is considered net __________________ work

negative, eccentric

net ____________________ work is performed by the quadriceps muscles as they lower the body down the stairs in a controlled fashion, during __________________ activation

motor, concentric

when standing up, biceps femoris acts as a __________________. is this concentric or eccentric?

brake, eccentric

when sitting down, biceps femoris acts as a ___________________. is this concentric or eccentric?

power

the rate of work production

rate of work production

define power

work/time

equation for average power

force x velocity

equation for instantaneous power

false

true/false: equations for average and instantaneous power are the same

linear

is instantaneous power linear or angular?

watts

units for power

more, less

_____________ work in _____________ time = efficient

Fd/t (work = Fd)

breakdown of average power equation

inverse

there is a __________________ relation between a muscle's max force potential and its shortening velocity

power

the inverse relationship between a muscle's max force potential and its shortening velocity is related to the concept of what?

as the velocity of a contraction increases, concentric force decreases and eccentric force increases

describe the force-velocity curve

decreases, increases

force-velocity curve: as the velocity of a contraction increases, concentric force _________________ and eccentric force _________________

(see slide 8)

what does the force velocity curve look like?

false

true/false: power exercises are bad for older adults

the capacity to do work

what is energy?

Joules

unit for energy

3, kinetic (energy), potential (energy), strain (energy)

there are ______ forms of energy. name them

positive

if force and velocity have the same direction, you have _____________ (+ or -) power

negative

if force and velocity have the opposite direction, you have _____________ (+ or -) power

positive

if power is ________________, energy is generated --> concentric contraction

generated

if power is positive, energy is __________________ --> concentric contraction

concentric

if power is positive, energy is generated --> __________________ contraction

negative

if power is ________________, energy is absorbed --> eccentric contraction

absorbed

if power is negative, energy is _________________ --> eccentric contraction

eccentric

if power is negative, energy is absorbed --> ___________________ contraction

energy of motion

what is kinetic energy?

KE=1/2mv^2

equation for kinetic energy

energy of position (stored energy)

what is potential energy?

PE=mgh

equation for potential energy

height

what does potential energy depend on that kinetic energy does not?

energy cannot be created or destroyed, only transformed (between kinetic, potential, strain)

law of conservation of energy

=

KEmax ________ PEmax

strain

deformation of materials in response to stress

dimension, L/L

strain is expressed as change in __________________ (delta ________/_________)

none (units cancel)

units for strain

stress

internal force that resists strain

internal, strain

stress is an ________________ force that resists ____________

simple, complex

there are ______________ and _______________ stresses

compression, tension, shear

simple stresses (3)

review pictures on slide 15 for types of stresses

perpendicular

compression is __________________ to plane

perpendicular

tension is ________________ to plane

parallel

shear stress is ____________________ to plane

bending, torsion, complex loading

complex stresses (3)

tension convex, compression concave

describe bending stress

twisting (compression, tension, and shear)

describe torsion

all combinations of stress

what is complex loading?

true

true/false: each material has its own unique stress-strain curve

force/area

equation for stress

pascal(s)

unit for stress

percentage

strain is expressed as a ____________________

elastic

the ________________ region is the linear region of the stress strain curve

yield point

elastic limit of tissue

plastic region

non-linear response of the material after the yield point. some degree of deformation will persist after removal of the stress

elastic region

The area of a stress-strain curve before the yield point. The area in which the material will return to its resting length when the applied force is removed.

elastic (region)

will a material return to its resting length in the elastic or plastic region?

yield point

threshold at which permanent damage begins on a stress strain curve

toe region

stress strain curve: the area from initiation of the force to the beginning of fibril stretch

non linear

is the toe region of the stress strain curve linear or non linear?

microfailure (to) macrofailure

plastic region can range from ________________ to ________________

macrofailure

the point of ultimate stress and strain where the tissue fails completely and the stress in the tissue drops to zero

toe region

initial stress that results in the wavy collagen fibers becoming straight and aligning with one another

collagenous

the toe region is more pronounced in ____________________ tissue

ultimate stress, ultimate strain

macrofailure is the intersection of what two things?

hysteresis loop

a loop-shaped plot obtained when loading and unloading a material produce different deformations

loading, deformation

hysteresis loop occurs with elastic __________________ and plastic _________________

energy, lost, loading, internal friction

the difference between the two curves in the hysteresis loop represents the amount of _____________ that is ___________ during _________________ due to _________________

(see slide 18)

what does the hysteresis loop look like?

hysteresis

characteristic of viscoelastic materials where the loading curve does not follow the unloading curve because of energy loss

stress relaxation

a decrease in stress (force) when the strain is held constant (fixed deformation) for a given period of time

adapting

stress relaxation is about the tissue __________________

review stress relaxation graph on slide 19

length, time

stress relaxation deals with change of _______________ of tissue over ______________

creep

increasing deformation under constant load

slow deformation, time, fixed load

creep is a __________ __________________ over ____________ as a result of a _______________ ___________