Week 1 Lecture Notes Pt. 1

Kinematics

Answers "how an object moves”

Kinetics

Answers “why an object moves”

Translation

All parts of a rigid body move parallel to and in the same direction as every other part of the body (straight or curve line)

Rotation

All points in the body simultaneously rotate in the same angular direction

Osteokinematics

Describes motion of bones relative to the sagittal, frontal, and transverse planes (joint rotations)

Frontal

Sagittal

Horizontal

Three orthogonal planes

• _____ plane motion

– Rotate about A-P axis

• _____ plane motion

– Rotate about M-L axis

• _____ plane motion

A-P axis

M-L axis

– Rotate about S-I (vertical) axis

Axis

convex

_____ of Rotation (AOR): A straight line about which an object rotates

Most joint AOR are through _____ joint partner

Degrees of Freedom

The number of independent movements allowed at a joint

Open

_____ Kinematic Chain:

The distal segment of a kinematic chain (e.g., foot) is NOT FIXED to the earth or other immovable object

Closed

_____ Kinematic Chain:

The distal segment of a kinematic chain (e.g., foot) is FIXED to the earth or other immovable object

Arthrokinematics

Describes motions at the articular surfaces

–Roll

–Glide (Slide) –Spin

Roll

Slide

Spin

Motions between articular surfaces

– _____

• Multiple paired contact points between two surfaces

– _____ (glide)

• One single point of one surface contacts multiple points on another surface

– _____

• Single point of one surface rotates on a single point on another surface

Opposite

Same

Convex-Concave Rule:

• Convex surface movingon a fixed concave surface slides in the _____ direction of roll

• Concavesurfacemoving on a fixed convex surface slides in the _____ direction of roll

fixed

moving

direction

Identifying Movement:

1. Identify the _____ surface

2. Identify the _____ surface

3. Define the _____ of rolling

4. Identify the direction of sliding based on convex- concave rule

Force

A push or a pull that produces, arrests, or modifies a motion.

External

Internal

What are the forces applied to the human body?

1) _____ forces

Gravity: segment weight, body weight

External weight

2) _____ forces

Active: Musculotendinous unit (muscle force)

Passive

• Ligaments, fascia, etc.

– Tension under stretch

Internal forces vs. external : – To perform a task or activity

Vector

Unit with magnitude (length) and direction (arrow)

Head

Tail

Head-to-Tail method

1) Arrange all vectors so that the _____ of the previous vector is connected to the ____ of the next vector

perpendicular

Compressive

Distractive

Compression/Distraction – Normal force

By the force component _____ to the joint surface

• _____ force: ↑force to the joint surface; ↑stability

• _____ force: ↓force to the joint surface; ↓ stability

Shear

parallel

_____

– Tangential force

– By the force component _____ to the joint surface

• ↓ stability

Resultant

_____ Vector:

From the tail of the 1st vector to the head of the last vector

direction

Why resolve a vector?

– To know the effect of a vector on a specific _____

– The total effect of the vector can be replaced by the component vectors

Torque

Is the tendency of a force vector to rotate an object about some axis

= Force x Moment Arm

Moment Arm

_____ _____ (Lever Arm): Perpendicular distance from the line of applied force to the axis of rotation

First

_____ Class Lever:

Axis of rotation positioned between opposing forces

Second

_____ Class Lever:

• Axis of rotation positioned at one end of a bone

• Internal force (muscle force) has greater leverage than the external force

Third

_____ Class Lever:

• Axis of rotation positioned at one end of a bone

• External force has greater leverage than the internal force

Center of Mass

The point at which a body’s mass is equally distributed

Anterior to S2

Center of Gravity

The point at which the entire weight of a body may be considered as concentrated

• If being supported at this point, the body would remain in equilibrium in any position

Ground reaction force

The external forces exerted by the ground on an object in contact with it

Joint reaction force

The combination of all internal and external forces, such as muscle contractions, ligament tension, cartilage contact, and body weight, that are transmitted between bones at a joint

Free body diagram

A "snapshot” that represents the interaction between a system and its environment

• All relevant forces should be drawn