Kinematics and Kinetics

kinematics

motion of the body without regard to force

types of kinematics

osteokinematics and arthrokinematics

motions of osteokinematics

rotation and translation

motion of arthrokinematics

roll, slide, spin

example of osteokinematics and arthrokinematics during knee extension

osteo: knee extension, arthro: clockwise roll and posterior slide

when convex is moving on concave roll and slide are ____

opposite

when concave is movi roll ng on convex roll and slide are ____

same

roll is always in the _____ direction as the osteokinematic movement

same

consequence if roll is impaired

impingement

consequence if slide is impaired

dislocation

loose-packed joint position

point in the RoM where the capsule and ligaments provide the least amount of restraint

clinical implication of the loose-packed joint position

assess movement and joint play during evaluation

close-packed joint position

ligaments and capsule are strengthened and tight so there is max joint congruency

joint play

also called accessory motions; freedom of one joint surface to move on another

kinetics

forces involved in motion

center of mass at anatomical position

anterior to S2

center of mass and stability

center of mass must be inside the base of support to be stable

what influences the perpendicular and parallel components of vectors

position of body segment and weight

pathway of signal to a muscle

begins in upper motor neurons in precentral gyrus → goes to alpha motor neurons in the spinal cord → each neuron innervates a group of fibers

motor unit

one alpha motor neuron and all of the fibers it innervates

types of sensory organs in muscles

golgi tendon organ and muscle spindle

function of golgi tendon organ

detects the tensile force created when muscle contraction/stretch pulls on the tendon

function of muscle spindle

monitors the length and rate of the change of length

sarcolemma

outer covering of a muscle fiber

sarcoplasm

inside the cell (cytoplasm)

sarcoplasmic reticulum

surrounds the myofibrils

terminal cisternae

enlarged SR tubules

t-tubule

opening in the sarcolemma that extends into the cell

components of the triad

terminal cisternae and t-tubules

z disc

anchor for actin molecules

a band

dark band with actin and myosin

m line

center of a band where myosin anchors

h zone

part within the a band where actin and myosin do not overlap

i band

light band with only actin

function of titin

contributes to muscle passive force when the muscle is stretched

components of neuromuscular junction

axon terminal, motor end plate, synaptic cleft

activity at the neuromuscular junction

vesicles in the axon terminal release Ach that binds to receptors on the motor end plate

muscle force couple

muscles that act in different directions on the same object to produce the same motion

anatomical and biomechanical factors of force production

fiber type, fascicle arrangement, PCSA, length-tension relationship, force-velocity relationship

twitch response

how long it takes the muscle to respond to stimulation

twitch response relationship to fatigue

faster twitch response → larger motor unti → greater force → quicker to fatigue

structure and function of fusiform fiber arrangement

long fibers run parallel to each other to produce large movements

structure and function of pennate fiber arrangement

shorter oblique fibers that produce large force

PCSA

cross-sectional area of muscle perpendicular to the orientation of muscle fibers that is directly proportional to the muscles ability to generate force

length-tension relationship during active force generation

there is an optimal sarcomere length required to produce the peak force

length-tension relationship during passive force generation

as the muscle gets longer, the active force drops and titin/CT takes over

parallel elastic components of muscle force

layers of CT on the muscle

series elastic components of muscle force

titin and tendons

force-velocity relationship

increase concentric force → slower velocity

why is isometric force used in MMT

it takes the velocity variable out of the measurement

neurophysical factors of force production

recruitment principle, rate coding/firing frequency, active insufficiency

recruitment principle

fibers are recruited sequentially based on the force required

rate coding

increase the rate of firing → increase force production

active insufficiency

decreased force output of muscle secondary to the that muscle being placed in a non-optimal length related to the length-tension relationship

effect of forces on tissues

different forces causes different loads and pain levels, too much load causes pain and impairment

effect of forces on joints

joint reaction forces are created between articular surfaces from internal and external forces

what is created by the perpendicular component of muscle force

joint rotation (muscular torque)

what is created by the parallel component of muscle force

joint reaction force

equation for torque

torque = force x moment arm

static equilibrium

point where the internal forces equal the external forces and nothing moves