AHM Exam 1 (Biomechanics)

Biomechanics

the application of the broad term mechanics to the study of human movement

What are the two branches of biomechanics?

Kinematics & Kinetics

Kinematics

Branch of mechanics used to describe movement of the body. (Osteokinematics & Arthrokinematics)

Kinetics

Branch of movement used to describe how forces and torques affect the body. (Force of a muscle acting on a bone)

Anatomical Position

Eyes looking forward

Feel parallel/slightly apart

Arms at side

Palms facing forward

Upright, weight evenly distributed

Rotation/twisting

opposing forces applied on each articulating surface. (can result in spiral fracture or tissue injury)

Anterior(ventral)

The front of the body

Posterior(dorsal)

The back of the body

Medial

Towards midline

Lateral

Away from midline

Distal

farther from the origin of a body part or the point of attachment of a limb to the body trunk

Proximal

Closer to the origin of the body part or the point of attachment of a limb to the body trunk

Superior

Above

Inferior

Below

Ipsilateral

On the same side of the body

Superficial

At the surface

Deep

Way below the surface

Contraladeral

On the opposite side of the body

Supine

Laying face up

Prone

Laying face down

Right lateral recumbent position

Laying on right side

Left lateral recumbent position

Laying on left side

Movement occurs

WITHIN a plane

AROUND an axis

Saggital plane

Passes through body vertically from front to back. (divides body into right & left halves)

Frontal plane

Passes through the body vertically from side to side. (divides body into posterior & anterior)

Transverse plane

Passes through the body horizontally. (divides body into superior & inferior)

Center of gravity

Point where all planes intersect

Degrees of freedom

The number of planes in which the joint can move. (Uniaxial, Biaxial, & Triaxial joints)

Force

The amount of push/pull applied to objects or body segments

Push creates

compression

Pull creates

traction

What are the two types of force that cause the body to move?

Internal & External

Internal Force

muscle contractions

ligamentous restraint

External Force

gravity

external weight

friction

Gravitational Force

Force exerted on an object or person by gravity

Linear force

two forces acting on the same line. (can pull in the same or opposite directions)

Parallel force

two forces acting in the same plane but opposite directions

Concurrent force

Two+ forces acting on a common point but push/pull in different directions

Force Couple

Two+ forced acting on a common point but opposite directions, resulting in a turning effect 🔄

Five possible mechanical effects of force

1. Traction

2. Compression

3. Shear

4. Bending

5. Rotation(twisting)

Traction

joint surfaces pull apart from each other. (ex. carrying a heavy bag)

Compression

joint approximation. (ex. push ups)

Shear

gliding motion where joint surfaces move parallel to each other. (excessive shear forces cause soft tissue injury)

Bending

forces are not applied equally. (compression on one side & elongation on the other)

Linear motion

Occurs more or less in a straight line. (same direction, distance, and time)

Rectilinear motion example

straight line. (ex bowling ball or sled)

Curvilinear motion

curved line. (ex. path of a ball or diving)

What are the two types of movement?

1. Linear motion

2. Angular motion(rotary)

Joints are considered

axes

Muscles and weight can be considered as

force & resistance

Bones are considered

levers

What are the three different types of levers?

First, Second, & Third class levers

First Class Lever

axis is in the middle

Second Class Lever

resistance is in the middle

Third Class Lever

force is in the middle

Muscles

attach to bones by tendons

produce movement at joints

do not know direction, they only contract

What are the two parts of muscles?

Insertion and origin

Insertion

usually on more moveable bone

tends to be more distal

Origin

usually on more stable bone

tends to be more proximal

What determines the action of a muscle?

Line of Pull

What are four characteristics of a muscle fiber?

1. irritability

2. extensibility

3. contractility

4. elasticity

Irritability(excitability) of a muscle

reacts to a stimulus by generating an electrical impulse that leads to contraction

Extensibility of a muscle

stretch or lengthen when force is applied

Contractility of a muscle

contract & generate force

Elasticity of a muscle

recoil or return to its normal resting length when stretching/shortening force is removed

Agonist(prime movers)

Muscle(or group of muscles) most directly involved in causing the motion

Antagonist

Performs opposite motion of agonist ; has capability of slowing/opposing the movement of the prime mover

What is Co-contraction?

When the agonist and antagonist muscles work together to stabilize

Synergist

When two+ muscles work together to perform a motion that cannot be performed by a single muscle

Isometric Muscle Contraction

muscle contracts without changing length of muscle

Isotonic Muscle Contraction

muscle contracts and changes the joint angle

a.) concentric (muscle shortens)

b.) eccentric (muscle lengthens)

Isokinetic Muscle Contraction

occurs when the speed of the motion stays the same for the duration of contraction but resistance varies.

What is tension?

force built up in a muscle due to stretching and/or contracting

What is muscle excursion?

the length difference between a muscle that is fully shortened and the same muscle fully lengthened

What can cross one joint or multiple joints?

Muscles

Active Insufficiency

multi-joint muscle shortens over two joints simultaneously, creating so much slack that tension is completely lost.

(occurs to the agonist)

Passive Insufficiency

multi-joint muscle is lengthened to its fullest extent at both joints, which prevents full ROM of each joint it crosses

(occurs to the antagonist)

What does ROM stand for?

range of motion

What are kinetic chains?

interconnected system of muscles, joints, and tendons that work together to produce movement

What are the two types of kinetic chains?

closed & open kinetic chains

Closed kinetic chain

occurs when distal segment is fixed.

(provides stability distally)

What are some examples of an open kinetic chain?

Reaching into cabinet

Kicking a ball

Brushing your teeth

Throwing a ball

What are some examples of a closed kinetic chain?

Squats

Wall push-up

Sit to stand

Going up stairs

Joint

connection between two bones

(allows movement

helps bear weight

provides stability

contains synovial fluid)

What is the purpose of synovial fluid?

lubricates joint

nourishes cartilage

Stability vs Movement

Increased Stability = decreased mobility

decreased stability = Increased mobility

What are two types of joints?

1. Synarthrodial

2. Diathrodial

Synarthrodial joints

provides shape and stability

allows little to no movement

Diathrodial joints (synovial)

provides mobility

cavity contains synovial joints

no direct union between bone ends

has a joint capsule

Joint capsule

outer layer - strong fibrous tissue(holds joint together & protects)

inner layer - lined with synovial membrane that secretes synovial fluid

Joint capsule also

Reduces friction

source of nutrition for tissues

Articular surface

smooth and covered in hyaline cartilage

more movement =

= less stability

What is the purpose of ligaments?

holds joints together

provides attachment for cartilage

flexible but not elastic

What contains fibrous connective tissue?

Cartilage

What are the three types of cartilage ?

1. Hyaline cartilage

2. Fibrocartilage

3. Elastic cartilage

Hyaline cartilage (articular)

covers ends of bone with a synovial joint.

cannot repair itself

no blood or nerve supply

Fibrocartilage

shock absorber

(ex. menisci of knee, vertebral discs, labrum)

elastic cartilage

helps to maintain shape

allows movement

(ex. ear)

Open kinetic chain

occurs when proximal segment is fixed.

(correcting muscle imbalances or rehab after injury)