kines midterm intro concepts and motor control

Kinesiology

study of human movement

kinematics

concepts that allow us to describe movement without regard to the forces that the movement

osteokinematics

motion of bones relative to cardinal planes

ex:flex,extend

arthrokinematics

motion occurring between articular joint surfaces

ex: roll, spin, glide

Kinetics

allows us to describe why a segment moves

(FORCES CAUSING MOTION)

rotary (angular) motion

movement around a fixed axis in a curved path

translatory (linear) motion

movement of a segment in a straight line

rectilinear

Each point of the segment moves through the same distance at the same time (in a straight line)

curvilinear (planar)

Combination of rotation and translation

• Axis of rotation is not fixed (instantaneous center of rotation-ICoR)

planes of motion

sagittal, frontal, transverse

sagital plane motions

Flexion/extension

Dorsiflexion/plantar flexion

Forward/Backward bending

frontal plane motions

Abduction/Adduction

Lateral Flexion

Ulnar/radial deviation

Eversion/inversion

transverse plane motions

Internal (medial)/External (lateral)

rotation

Axial rotation

Transverse plane axis of rotation

vertical axis

frontal plane axis of rotation

anterior-posterior axis

saggital plane axis of rotation

mediolateral (ML) axis

axis of rotation

an imaginary line about which a turning body such as earth rotates

degrees of freedom

Number of independent directions of movements allowed at a joint;A joint can have up to 3 degrees of angular freedom

kinematic chain

series of articulated segmented links

open chain

the distal end of the chain is free to move,

one it can move independent of the others

closed chain

distal end is fixed, movement at one joint

automatically creates movement in other joints

roll movement

Multiple points along one rotating

articular surface contact multiple points

on another articular surface

slide(glide) movement

A single point on one articulating surface

contacts multiple points on another

articular surface

spin movement

A single point on one articulating surface

contacts a single point on another

articulating surface

Convex on Concave

the convex member tends to roll and glide in opposite directions

Concave on Convex

the concave member tends to roll and glide in the same direction

Close pack position

Joint, soft tissue are maximally tensed, maximal contact between joint surfaces. Joint play and mobilization cannot be properly performed in this position

open pack position

Loose; least amount of joint congruency and the joint capsule and ligaments are most loose.

force

A push or a pull that results from physical contact between two objects

external force

- Gravity- 9.8m/s2

- External load

- Physical contact (i.e., therapist generated)

internal force

- Active=muscle

- Passive=tension

magnitude of displacement

equals the straight-line distance between the starting and ending positions, without regard to direction

ROM

magnitude a segment can (or does) move through

speed

displacement per unit time

regardless of direction

velocity

displacement per unit time

in a given direction

acceleration

velocity per unit time, velocity is changing over time

vectors

An arrow representing both magnitude and direction of a force

- Length is proportional to magnitude

- Direction is indicative of the direction of the movement

• Commonly used in biomechanical analyses to represent forces (i.e., muscle, joint reaction or resistance forces)

Force vectors

Arrows representing magnitude and direction of forces.

LoG (line of gravity)

always towards the Earth

CoG (center of gravity)

the hypothetical point at

the center of an object's

mass; when considering several it combines and moves to heaviest mass

CoM (center of mass)

Located anterior to S2

• With rearrangement of the

segments of the body, CoM moves

- Amount of movement depends on

how disproportionately segments are

arranged

Newton's First Law: inertia

A body remains at rest or in uniform motion (moving with a given speed and direction) unless acted on by an external

force to change its state

static equillibrium

when velocity is zero (motionless)

dynamic equillibrium

when velocity is not zero but is constant

(in motion)

inertia

amount of energy required to alter the velocity of body

- Directly proportional to mass

Newton's Second Law: acceleration

Acceleration of an object is proportional to the F causing accel & inversely proportional to the mass of the object

- Acceleration = F/m (F=ma)

- Direction will be in the direction of unbalanced force

Newton's Third Law: reaction

For every action there is an equal and

opposite reaction

i.e., Ground reaction force

linear force system

two or more forces act on the same segment, same plane and same line

concurrent forces

Two or more forces acting on a common point but pulling or pushing in different directions.

resultant forces

overall force acting on something after you combine all the forces pushing or pulling on it.

tensile force

pulling an object in opposite directions

distraction force

a net force that moves a bony segment away from its adjacent bony segment

joint reaction force

two segments of a joint are pushed together and press back against each other

compression force

two forces that cause the joint reaction force

shear force

any force that has an action parallel to contacting surfaces and creates or limits movement between surfaces

friction force

potentially exists on an object whenever there is a contact force on that object

stress

force generated (internal resistance) per cross sectional unit of material (F/unit area) as the tissue resists

deformation

strain

percentage of change in the length or cross-section of a structure

stress-strain curve

Graph showing relationship between stress and strain.

Toe region of stress-strain curve

Non-linear because collagen fibers need to be drawn taut before significant tension can be measured

elastic region of stress-strain curve

When the force is released, there is no permanent change (deformation) in shape

yield point of stress-strain curve

Transition point between elastic

& plastic region

plastic region of stress-strain curve

increasing in strain with little

change in stress. Force results

in permanent deformation

ultimate failure point of stress-strain curve

Final rupture of the material

Visoelasticity

combination of elastic and plastic properties, which allows soft tissues in the body to return to their original shape after stretching (elasticity) and to adapt to sustained periods of stretch (plasticity)

creep force

Force remains constant, length changes over time (continued deformation of material over time with constantload)

- Eg. Hold hamstring stretch for 2' causes it to gradually

lengthen

stress-relaxation

Force decreases over time; length remains the same

- Eg. Stretch shoulder capsule and hold it into place, the force that you need to hold the stretch decreases

If a force is applied through an object's

CoM

linear displacement will occur

force couples

2+ muscles simultaneously produce forces in different linear directions with torques that act in the same rotary direction

moment arm/lever arm

the perpendicular distance between

a force and the axis of movement

torque

the strength of the rotation (also

called moment of force)

The shorter the moment arm

the greater the amount of force needed to create movement

moment arm is greatest when

the force is perpendicular to the

lever

lever

functions to produce rotatory torque out of a linear force; consists of rigid body with two applied forces and a point of

rotation

first class lever

A first-class lever is a lever where the fulcrum is in the middle between the effort and the load.

rare

MA >,

second class lever

the load is in the middle between the fulcrum and the effort.

rare

MA >1

third class lever

A third-class lever is when the effort is in the middle between the fulcrum and the load.

MA < 1

mechanical advantage

Mechanical advantage is how much a lever or machine increases the force you apply, making it easier to move a load.

synarthroses joint

immovable joint, reinforced by fibrous and cartilage connective tissue

diarthroses joint

synovial fluid filled cavity that is freely movable

ex: GH joint

fibrous joint

immoveable and held together by ligaments only

ex. teeth in socket

cartilaginous joint

two or more bones joined by cartilage

uniaxial joint

type of diarthrosis; joint that allows for motion within only one plane (one axis)

hinge or pivot

biaxial joint

type of diarthrosis; a joint that allows for movements within two planes (two axes)

condyloid, ellipsoid, saddle

triaxial joint

moves in more than two planes, such as flexion/extension, abduction/adduction, and rotation. Ball and socket joints and plane

connective tissue

capsule, ligament, tendon, articular and fibrocartilage, bone

fusiform muscle

fibers run parallel to one another and to the central tendon ex: biceps

pennate muscle

fibers that approach their central tendon obliquely

• most muscles

• generate large force

• unipennate, bipennate or multipennate

Physiologic cross-sectional area

reflects the amount of

active proteins available to generate contraction force

• maximal force potential is proportional to the sum of the cross-sectional area of all of its fibers

• thicker muscle generates more force than thinner

Pennation angle

angle of orientation between muscle fibers and tendon; less force from each fiber goes straight to the tendon.

passive tension curve

- caused by the elasticity of the muscle (it is made of stretchy proteins)

- does not involve actin/myosin interaction

active length tension curve

how much force a muscle can make depends on how long or short it is when it contracts.

- A muscle makes its most force near its normal/resting length.

-If the muscle is too stretched or too shortened, it makes less force.

- That happens because there are fewer cross-bridges between actin and myosin.

total length tension curve

-passive and active together

-as muscle fiber is further stretched, passive tension dominates curve (lengthened and weak)

isometric contractions

length of muscle

unchanged, internal and external forces matched

concentric contractions

muscle contracts,

internal torque exceeds external torque

eccentric contraction

muscle lengthens,

external torque exceeds internal torque

force-velocity curve

how the speed of a muscle contraction affects how much force the muscle can produce

concentric conctraction + force

muscle shortens. The faster it shortens, the less force it can produce

eccentric contraction+ force

muscle lengthens while resisting. The faster it lengthens, the more force it can handle.

muscles are stronger

eccentric