Tufts DPT Movement Science Exam 1 Biomechanics (Weeks 1-3)

Kinesiology

study of human movement

Biomechanics

the application of physics principles to biological systems

Kinematics

branch of mechanics that describes the motion of a body without regard to the forces or torques which produce this motion

*movement*

Kinetics

branch of mechanics that describes the effect of forces on the body

*force*

Axis of rotation of a joint

varies based on the position of the joint

Rectilinear translation

when all points on a body move in a straight line, the same distance, and with no change in direction

Curvilinear translation

occurs when all points on a body move the same distance but the paths followed by the points on the object are curved

Osteokinemetics

Rotational movement of one bone on another

-measured w goniometer

Arthrokinematics

Gliding motions of the joint surfaces that may accompanythe joint rotations to allow for normal joint motion

-measured w joint play or arthrometers

open chain

distal segment is free to move

closed chain

distal segment is fixed

Convex on concave

roll and slide in opposite directions

Concave on convex

roll and slide in same direction

Closed pack position

-joint position wherethere is maximal congruency of the joint surfaces

-Joint position which places maximal tension on the joint capsule and ligaments

Open pack position

-any position which is not closed pack

-Joint position which has minimal joint congruency of the joint surfaces

-accessory movements allowed

Strain

measure of the amount of deformation of an object

Stress

internal force generated as a tissue resists deformation, divided by its cross-sectional area

Types:

-compression

-tension

-shear

Bone vs stress

good at compression

bad with shear

Zone A

A: the toe region. Slight stretch produces minimaltension in a nonlinear relationship.

Zone B

Zone B—the elastic zone. Increasing stress and strain are present in a linear relationship. Tissue can return to its original shape when the force is removed.

Zone C

Zone C—the plastic zone. The tissue continues to elongate while thereare only slight increases intension. It is at this point there is microscopic tissue failure. The tissuedoes not return to its original shape when the force is removed—it ispermanently deformed

Zone D

Point D—initial point of failure, yield point

Zone E

Point E—Complete failure

elastic region

should not cause tissue damage

plastic region

may cause tissue damage

Creep

Type of tissue elongation: constant loading

Stress Relaxation

Type of tissue elongation: constant deformation

isometric contraction

same length while contracting

concentric contraction

muscle shortens while contracting

eccentric contraction

muscle lengthens while contracting

Agonist muscles

muscle or muscle group that contracts to cause movement during an isotonic exercise

Antagonist muscles

muscles that oppose or reverse a particular movement

Synergist muscles

assist prime movers during movement

Force couples

when two or more musclessimultaneously produce forces indifferent linear directions, although theresulting torques act in the same rotarydirection

Productive antagonist

model of 2 antagonistic muscleswhich when acting on a specific task provideactive and passive assistance to the task

Plyometric

-Specific muscle contraction where an eccentric contraction is immediately followed by a concentric contraction

-Plyometric contraction can produce greater than concentric, isometric, or eccentric contraction due to• Utilization of elastic energy within the soft tissues• Stretch (myotatic) reflex assistance with concentric contraction

Force (Load) equation

F=ma

Force

Mass

Acceln

Rotation equation

T = I α

T = torque;

I = mass moment of inertia

α = angular acceleration

Newton's first law

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Newton's second law

Force = mass x acceleration

Center of mass

the point in an object that moves as if all the object's mass were concentrated at that point

Newtons third law

For every action there is an equal and opposite reaction

Joint Reaction Force

force that exists at a joint, developed in reaction to the net effect of internal and external forces

Torque can also be called ............

moment

External Moment Arm

Steps to determine EMA

1. Determine center of mass/gravity of segment of interest

2. Draw gravitational force acting at center of mass; you may need to extend the line above to help determine moment arm

3. Find the perpendicular between the joint of interest

internal moment arm

perpendicular distance between the axis of rotation and the internal (muscle) force

Posture

Relative arrangement of the parts of the body

Balance Requirement

Requirement - maintain the body's center of gravity within the object's base of support (BoS)

Ideal standing posture center of gravity

Line of gravity falls posterior to the hip and creates external extension moment

Line of gravity falls anterior to the knee and creates external extension moment

Line of gravity falls anterior to the ankle and creates external dorsiflexion moment

First class lever

fulcrum in the middle

second class lever

the axis of rotation is at one end of a system with the load and effort at increasing distances away

Third Class lever

axis of rotation is at one end of a system with the effortand load at increasing distances away

First class lever anatomic example

The axis of rotation is between the muscle force and external load

Second class lever anatomic example

The external force, the effect of gravity, on the system is closer to the axis of rotation than the muscle force

third class lever anatomic example

The muscle force is closer to the axis of rotation than the external force, effect of gravity, on the system

Mechanical Advantage

Mechanical Advantage (MA) of a musculoskeletal lever is the ratio of its internal and external moment arms: IMA/EMA

MA=IMA/EMA

MA > 1 higher force potential

MA < 1 lower force potential

Scalars

quantities that have only a magnitude (do not include direction)

Vector Construction

quantities that have both a magnitude and a direction

Vector Resolution

vectors

quantities that have both a magnitude and a direction

Anatomical pulleys

Types of pulleys

fixed

moveable

Equation for internal and external torque

Torque = magnitude of the resultant force x perpendicular moment arm

Diarthrosis Joints (7 characteristics + examples)

-synovial joint, free moving joints

-moderate to extensive movement

1. Synovial fluid 2. Articular cartilage 3. Joint capsule 4. Synovial membrane 5. Ligaments 6. Blood vessels 7. Sensory nerves

Examples:

Knee, Ankle, Shoulder, Apophyseal (facet spine)

Synarthroses Joints characteristics (2 types+examples)

Little to no movement

Fibrous Joints: Stabilized by specialized dense connective tissues, usually with a high concentration of collagen

Ex: Skull Sutures, tibiofibular

Cartilaginous Joints: Stabilized by varying forms of flexible fibrocartilage or hyaline cartilage, often mixed with collagen

Ex: Pubic Symphysis, spinal interbody joint

types of synovial joints

plane, hinge, pivot, condyloid, saddle, ball and socket, ellypsoid

Synovial Joint TypesPrimary Angular Motions

tissue types

epithelial, connective, muscle, nervous

Types of collagen

Type I thick, rugged fibers that elongate little when stretched; comprise ligaments, tendons, fascia, and fibrous joint capsules

Type II thinner than type I fibers; provide a framework for maintaining the general shape and consistency of structures, such as hyaline cartilage

Elastin

Netlike interweaving of small fibrils that resist tensile (stretching) forces but have more "give"when elongated

Ground Substance Glycosaminoglycans (GAGs)

-GAGs are a family of polysaccharides

-Negative charged to repel each other

Fibroblasts

Primary cells within ligaments, tendons, andother supportive periarticular connective tissues

Chondrocytes

Primary cells within hyaline articular cartilage and fibrocartilage

dense connective tissue

dense regular (tension), dense irregular (multiple planes), elastic

Most of the non-muscular soft tissues surrounding a joint

a. Fibrous layer of the joint capsule

b. Ligaments

c. Tendons

low healing capacity bc of bloodflow

Dense ConnectiveTissue Remodeling and Repair

Loading tissue - healing

immobilization - decrease load tolerance- weaker

Articular cartilage

hyaline cartilage

decrease compressive load and friction

minimal blood + nerves

Cyclic loading promote tissue health and remodeling

Fibrocartilage

1. Mixture of dense connective tissue and articular cartilage

2. Support and stabilize joints, guide arthrokinematics, dissipate forces

3. Limited vascular and neural supply

4. Combines properties of both dense connective tissue and articular cartilage

a. Intervertebral discs

b. Labrum; shoulder and hip

Compact bone

Hard, dense bone tissue that is beneath the outer membrane of a bone

Cancellous Bone

spongy, porous, bone tissue in the inner part of a bone

Wolff's law of bone

architecture of bone determined by mechanical stresses placed on it and bones adapt to withstand those stresses

Bone healing capabilities

high; rich blood supply

Clinical implications (What forces can be used for tendon, capsules, bone, cartilage)

a. Tendon = tension

b. Capsule = tensions

c. Bone = compression

d. Cartilage = compression

prolonged muscle lengthening

increase sarcomeres, may lead to stretch weakness

prolonged shortening

Decrease in number of sarcomeres secondary to lack of tension

Slower velocity contractions during a concentric contraction allows more time to:

1. remove slack in the muscle

2. increase electrical signaling

3. increase muscle fiber recruitment

Faster velocity contractions during an eccentric contraction take advantage of the:

1. passive elastic properties of the musculotendinous unit and

2. requires less energy, ie, ATP, since less energy require; result of mechanical breakage of actin/myosin cross bridge

Internal Torque (Moment) vs Joint Angle Curve (Picture)

Muscle Force Generation

Muscle force is created as a combination of both active and passive component contributions

Active: contraction

Passive: Stretch of non contractile elements - non contractile proteins, tendons -mysiums

Linear decline in maximum tension vs angle curve

A parabola shaped curve ^

Linear decline: the dominant factor determining the strength of the muscle is the length-tension relationship

Parabola: the moment arm impacts the overall strength of the muscle, typically in midrange

Ex: biceps, quadriceps

Force potential of contractions

Eccentric > isometric > concentric

Concentric: ↑ velocity = ↓ force

Eccentric: ↑ velocity = ↑ force