body mechanics.ppt

7/27/2019 Body Mechanics.ppt

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BODY MECHANICS



Body mechanics

• the efficient use of the body as a

machine and as a means of locomotion

• concepts most helpful to the

understanding of body mechanics:

– body alignment,

– balance,

– coordinated body movement, and

– joint mobility



Body Alignment

• the geometric arrangement of body parts inrelation to each other;

• synonymous with good posture

•benefits of good body alignment:

– optimal musculoskeletal balance and operation

– healthy physiologic functioning without undue

strain on the joints, muscles, tendons, or

ligaments in any position, e.g.:• standing

• sitting

• lying



application of correct body

alignment when standing

• the head is held erect

• the face is in the forward position, in thesame direction as the feet

• the chest is held upward and forward

• the spinal column is upright, and thecurves of the spine are within normal

limits• the abdominal muscles are held upward

and the buttocks downward



application of correct body

alignment when standing

• the knees are extended - not bent or hyperextended in the knee-locked position

• the feet are at right angles to the lower

legs• the line of gravity goes through the center

of the knees and in front of the ankle joint

• the base of support is on the soles of thefeet, and weight is distributed through the

soles and heels



balance

• the state of equilibrium in which opposing

forces counteract each other

• concepts most helpful to understanding

balance:

– base of support,

– center of gravity, and

– line of gravity



Balance

– base of suppor t

• the foundation on which an object rests

– center of gravi ty

• the point at which all of the mass of an object iscentered

• located in the center of the pelvis about midway

between the umbilicus and symphysis pubis

– l ine of gravi ty

• an imaginary vertical line drawn through an

object's center of gravity and base of support



Balance

• good balance is accomplished by:

– a wide base of support

• to widen the base of support, spread the feet

further apart

– a low center of gravity

• to lower the center of gravity, flex the hips and

knees until a squatting position is achieved

– a line of gravity through the center of gravity

and base of support



Balance

• conversely, poor balance is

accomplished by:

–

a narrow base of support –a high center of gravity

–a line of gravity which falls near the

edge of or outside of the base of supportor is constantly changing



coordinated body movement

• the production of balanced, smooth, and

purposeful movement

– coordinated body movements are

accomplished through the following:

• use of major muscle groups rather than weaker

ones, e.g.:

– flexors, extensors, and abductors of the thighs

– flexors and extensors of the knees

– flexors and extensors of the upper and lower arms



coordinated body movement

• use of the arm bones as levers and the elbows

as fulcrums to facilitate lifting a weight against

resistance (force of gravity)

• use of a pull sheet and smooth, dry, firm bedfoundation to decrease the effect of friction

which increases the amount of effort required

to move an object

• working close to the object to be moved to

decrease the effort involved



coordinated body movements•

coordinated body movements are alsoaccomplished through the integrativefunction of antagonistic, synergistic, andantigravity muscle groups

– antagonistic muscle groups • muscle group that brings about movement at a

joint by contraction of a prime mover andrelaxation of its antagonist, e.g.:

– to flex the arm, the prime mover (biceps brachii)contracts while its antagonist (triceps brachii) relaxes

– to extend the arm, the new prime mover (triceps brachii)contracts while its new antagonist (biceps brachii)

relaxes



coordinated body movements

• synergistic muscle groups

– muscle group that brings about movement at

a joint by strengthening the contraction of

the prime mover, e.g.:

• to flex the arm, the contraction of the

prime mover (biceps brachii) is

strengthened by contraction of itssynergist (brachialis)



coordinated body movements

– antigravity muscle groups

• bring about and maintain an upright or

sitting posture by contracting and/or

relaxing to oppose the effect of gravity onthe body

• e.g., extensors of the leg, gluteus

maximus, quadriceps femoris, muscles of the back



postural reflexes

• coordinated body movements are also

accomplished through the integrative

functioning of postural reflexes, e.g.:

– labyrinthine sense

• assists in producing coordinated body movement

by alerting an individual to movement of the head

in relation to gravity through stimulation of

receptors in the semicircular canals in the inner

ear



postural reflexes

• visual or optic reflex

– assists in producing coordinated body

movement by alerting the brain of thespatial relationships within the

environment (e.g., nearness of

ceilings, walls, furniture, condition of

floor) through stimulation of receptorsin the visual special sense



postural reflexes

• proprioceptive or kinesthetic

sense

–

assists in producing coordinated bodymovements by alerting the brain of the

location of a limb or body part in space

through stimulation of proprioceptive

receptors in muscles, tendons, and

fascia



joint mobility

• the complete extent of

movement of which a joint

(area when bone surfacescome into close contact with

another or articulate) isnormally capable



types o f jo in ts

• synarthroidal

– immovable joints

–

examples:• skull sutures,

• epiphyseal plates,

• joint between first rib and manubrium of

sternum



types o f jo in ts

• diarthroidial

– freely movable joints

• consistent features of diarthroidial joints

– ability to move freely

– a fibrous joint capsule

– a joint cavity

– a synovial membrane that lines the inner surface of the

joint capsule

– lubricating synovial fluid secreted by the synovial

membrane

– articular cartilage that covers the bony surfaces



types of diarthroidial joints

• ball-and-socket

• ball-shaped head fits into

concave socket of another bone• examples:

– hip joint between the femur and

pelvis




• condyloid

– oval-shaped condyle

(protuberance at the end of abone) fits into elliptical (oval, egg-

shaped) cavity of another bone

• examples: – wrist joint between the radius and

carpals




• hinge

– spool-like surface fits into

concave surface of another bone

•

examples: – elbow joint between the humerus

and ulna and radius




• pivot

– arch-shaped structure rotates

about rounded, or peg-like,pivot

•

example:» joint between the atlas and axis




– saddle

• saddle-shaped bone fits into a

socket that is convex on oneside and concave on the other

– example:

» thumb joint between thetrapezium and metacarpal



types of diarthroidal joint

movements

• flexion

– decreasing the angle of the joint

• e.g., bending the elbow

• extension

–

increasing the angle of the joint• e.g., straightening the elbow




movements

• hyperextension

– further extension or straightening of

the joint

• e.g., bending the head backward

• abduction

–movement of the bone away from themidline of the body

• e.g., moving the leg out to the side




movements

• adduction

– movement of bone toward the midline

of the body

• e.g., moving the leg back to the other leg

• rotation

–movement of the bone around itscentral axis

• e.g., turning the head




movements

• circumduction

– movement of the distal part of the bone in a

circle while the proximal end stays fixed

• e.g., moving each leg up, to the side, and downin a circle

• eversion

–

turning the sole of the foot outward bymoving the ankle joint



• circumduction

– movement of the distal part of the bonein a circle while the proximal end stays

fixed• e.g., moving each leg up, to the side, and

down in a circle

•

eversion – turning the sole of the foot outward by

moving the ankle joint



• supination

– moving the bones of the forearm so

that the palm of the hand faces upward

when held in front of the body

• protraction

–

moving a part of the body forward inthe same plane parallel to the ground

• e.g., jutting chin out



• retraction

– moving a part of the body

backward in the same planeparallel to the ground

• e.g., tucking chin in



principles of body mechanics

• the wider the base of support, the greater the

stability of the nurse

• the lower the center of gravity, the greater the

stability of the nurse• the equilibrium of an object is maintained as

long as the line of gravity passes through its

base of support

• the stronger the muscle group, the greater

amount of work that can be safely done by it



• facing the direction of movement prevents

abnormal twisting of the spine

• dividing balanced activity between arms

and legs reduces the risk of back injury

• leverage, rolling, turning, or pivoting

requires less work than lifting



• when friction is reduced between the object to

be moved and surface on which it is moved,

less force is required to move it

•reducing the force of work reduces the risk of injury

• maintaining good body mechanics reduces

fatigue of the muscle groups

• alternating periods of rest and activity helps to

reduce fatigue



application of the principles of

body mechanics• develop a habit of erect posture (correct alignment)

• use the longest and the strongest muscles of the armsand the legs to help provide the power needed instrenuous activities

• use the internal girdle and a long midriff to stabilize thepelvis and to protect the abdominal viscera whenstooping, reaching, lifting, or pulling

• work as closely at possible to an object that is to belifted or moved

• use the weight of the body as a force for pulling or pushing



• slide, roll, push, or pull an object rather than lift itto reduce the energy needed to lift the weightagainst gravity

• use the weight of the body to push an object by

falling or rocking forward and to pull an object byfalling or rocking backward

• spread the feet apart to provide a wider base of support when increased stability of the body isnecessary

• flex the knees, put on the internal girdle, andcome down close to an object that is to be lifted

body mechanics.ppt

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