OT503: Biomechanic Basics

Force

A push or pull of matter

Tensile force

pulling

Compressive force

pushing

Moment

Turning effect of force (torque)

Action

Specific motion a muscle can generate at a joint

Another term for lever arm

Moment arm

Moment arm

Distance from the joint axis to the muscle

Mechanical advantage

leverage

The moment arm is perpendicular to _____

the line of pull of the muscle

What is the order of the forces and axes of a first-class lever?

EAR

What is an example of a first-class lever on the human body?

Human neck

What is the order of the forces and axes of a second-class lever?

ARE

What is an example of a second-class lever in the human body?

The ankle

What is the order of the forces and axes of a third-class lever?

AER

What is an example of a third class lever in the human body?

Elbow

What is the most common lever in the human body?

Third-class lever

Joint reaction force

force generated within the joint in response to external forces acting upon it

Stress

Amount of applied force per area

Strain

Amount of material displacement under a specific amount of stress

Elasticity

The ability to stretch and return to the original shape

Elastic deformation

Ability to return to normal shape after strain

Yield point

The maximum amount of stress that can be sustained before tissue failure

Plastic deformation

Permanent deformation of tissue but retains continuity

What two things are bones mostly made from?

Collagen and calcium

Cortical/cancellous bone has greater mineral content?

Cortical

Cortical/cancellous bone makes up the shaft of long bones

Cortical

Cortical/cancellous bones have higher collagen content

Cancellous

Cortical/cancellous bones are found in the marrow cavity and at the end of long bones

Cancellous

What covers the ends of long bone along with the cancellous bone?

Articular cartilage

Articular cartilage is mostly ______

hyaline

What is the purpose of articular cartilage on the bone?

Absorbs forces between bones

True/False: Articular cartilage is one layer of CT on the ends of long bones

False; it’s multilayered

Osteoarthritis

Degeneration of cartilage within a joint

What do ligaments connect?

Bone to bone

What do tendons connect?

Muscle to bone

Ligaments/tendons contribute to joint stability

Ligaments

Ligaments/tendons help transfer forces

tendons

Joint capsule

Dense fibrous sleeve around the synovial joint

The joint capsule offers active/passive stability

passive

Aponeurosis

Fibrous insertion that connects adjacent muscles

The aponeurosis of the abdonimal muscles forms which structure?

Rectus sheath

What provides force for a fucntional movement?

Muscle

Myofibrils

Long cylindrical strands of contractile proteins

Sarcomere

Contractile units of a muscle

The thin filaments of a muscle are ____

actin

The thick filaments of a muscle are

myosin

Actin/myosin forms the central shaft of each sarcomere

Myosin

Motor Unit

A single motor neuron and the muscle fiber it innervates

The muscle is strongest in ______ position

midrange

True/false: The commands of a motor neuron are all-or- none

True

Fascia

Noncontractile tissues within the muscle

Flaccid muscle

Floppy results from loss of innervation to a muscle

Hypertonia

Muscle with increased tone

Muscle spindles

Elongated and encapsulated structures within muscle fibers that signal changes in muscle length and protect muscles

Which type of muscle fibers have a low force over a long period of time

Slow-twitch

Which muscles fibers allow for a powerful contraction

Fast-twitch

Type 1 fibers are _____

Slow-twitch

Type 2 are _____ fibers

Fast-twitch

_______ are located at the junction of muscle and tendon and are more sensitive than spindles

Golgi Tendon Organs

What does the GTO do?

Senses how much tension a muscle is exerting and causes the muscle to relax when necessary

The GTO is the opposite of the ______ ______

muscle spindle

Resistive force

resistance, usually from the weight of body or from carrying an object

Exerted force

The effort or internal force from muscles

The farther the muscle position and its generated force from the axis/joint, the smaller/larger the mechanical advantage and the faster/slower the speed of motion

Larger; slower

Adaptive shortening occurs when the muscles increase/decrease in length because of a/no force

decrease; no