Movement Week 1

Kinesiology Concepts

Kinesiology

integration of anatomy and biomechanics studying human movement and occupational performance

Statics

study of bodies at rest or moving at constant velocity in equilibrium

Dynamics

study of moving systems, categorized into kinetics and kinematics

Kinematics

study of motion describing time, space, mass, displacement, velocity, acceleration, and joint angles

Kinetics

study of internal and external forces acting on the body to generate motion

Force

any influence causing an object to change direction, movement, or structure (push or pull)

Internal Force

muscle contractions, passive resistance of ligaments, and elastic tissue properties counteracting external loads

External Force

forces arising outside the body, including gravity, friction, wind, water, and contact objects

Force Vector

quantified force defined by magnitude, direction, point of application, and line of action

Point of Application

specific location where a force acts upon an object (ex. finger touching a book)

Action Line

direction along which a force is exerted towards an object

Newton’s 3 Laws of Motion

1. Inertia

2. Acceleration

3. Action & Reaction

First Law: Inertia

objects remain at rest or uniform motion unless acted upon by unbalanced forces

Inertia

object’s resistance to change in movement; greater mass requires greater force magnitude

Equilibrium Rule

only forces with points of application directly on an object contribute to equilibrium

Momentum Equation

Momentum (p) = mass * velocity

Second Law: Acceleration

acceleration is proportional to force magnitude and inversely proportional to object mass

Acceleration Trigger

occurs when static inertia is overcome and physical movement begins

Force Equation

Force (F) = Mass (m) * Acceleration (a)

Third Law: Action & Reaction

for every action force, an equal and opposite reaction force acts simultaneously

Force Pairing

all forces occur in pairs when two contacting objects exert forces on each other

Friction

force resisting relative motion between two contacting surfaces, parallel to surfaces and opposing shear

Shear Force

external applied force required before friction force develops magnitude between contacting surfaces

Static vs Kinetic Friction

static friction is higher than kinetic friction after surface movement commences

Synovial Fluid

decreases friction within healthy joins during movement

Rheumatoid Arthritis

reduced synovial fluid increases joint friction, accelerating wear and causing pain

Linear Force System

two or more forces acting along identical action lines producing tension or compression

Concurrent Force Systems

forces applied at a common point acting in divergent directions

Parallel Force Systems

parallel forces acting on same plane at varying distances from rotational axis

Torque

force with a twist producing rotational acceleration around a joint axis

Torque Equation

Torque = Force * Moment Arm

Torque Examples

opening doors, turning water faucets, using jar openers, turning wrenches

Lever

simple machine comprising a rigid bar (bone) and axis (joint) converting force to torque

Effort Arm (FA)

perpendicular distance between rotational axis and EFFORT force line of action

Resistance Arm (RA)

perpendicular distance between rotational axis and RESISTANCE force line of action

Mechanical Advantage Equation

MA = Effort Force Effort Arm / Resistance Force * Resistance Arm

Efficiency Threshold

MA > 1 increases lever efficiency; MA < 1 decreases lever efficiency

Mnemonic: 123 ARE

1st Class: Axis in middle

2nd Class: Resistance in middle

3rd Class: Effort in middle

Examples of First Class Lever

neck extension (atlanto-occipital joint); crowbar; seesaw

Examples of Second Class Lever

heel raise (gastrocnemius/metatarsals); wheelbarrow; nutcracker

Examples of Third Class Lever

elbow flexion (biceps); tweezers; chopsticks