Kinese exam 1 BIOMECHANICS Lessons

Kinematics

Description of body movement (WHAT moves).

Static Kinematics

Body is still.

Dynamic Kinematics

Motion caused by unbalanced forces.

Kinetics

Study of forces causing movement (WHY movement occurs).

Static Kinetics

Net force on body equals zero.

Dynamic Kinetics

Net force on body does not equal zero.

Simple Machines

Devices that alter force or movement.

Simple Machines Types

Levers, wheels and axles, pulleys.

Simple Machines Purposes

Balance forces, increase force, increase ROM/speed, change direction of force.

Mechanical Advantage (MA)

Body posture that allows optimal joint function.

Mechanical Advantage Benefits

Increased strength, endurance, power, speed, ROM, and recovery.

Posture (Mechanical Advantage)

Balance between flexibility and strength.

Static Control

Strength required to gain and maintain posture.

IMA (Ideal Mechanical Advantage)

Theoretical measure of force multiplication by a machine.

Lever

Rigid bar rotating around an axis (fulcrum).

Axis/Fulcrum

The joint where movement occurs.

Resistance Arm

Distance from axis to resistance.

Force/Effort Arm

Distance from axis to applied effort.

First Class Lever (FAR)

Axis between force and resistance; balance or alter force/ROM. Example: seesaw.

Second Class Lever (ARF)

Resistance between axis and force; increases force. Example: wheelbarrow.

Third Class Lever (AFR)

Force between axis and resistance; increases speed and ROM; most common in body. Example: biceps curl.

Wheels and Axles

Modified levers that increase efficiency. Example: door knob, wheelbarrow.

Fixed Pulley

Mechanical advantage = 1; changes direction of force.

Movable Pulley

Mechanical advantage equals number of supporting rope segments.

Pulley System

Combination pulleys increasing mechanical advantage.

Human Motion

Human joint rotations combine to create linear movement from point A to B.

Rectilinear Motion

Straight-line movement.

Curvilinear Motion

Movement along a curved path.

Rotary Motion

Movement around an axis.

Oscillatory Motion

Back-and-forth swinging motion.

Newton’s First Law (Inertia)

Objects remain at rest or in motion unless acted on by an external force.

Newton’s Second Law (Force)

Force = mass × acceleration.

Newton’s Third Law (Action-Reaction)

Every action force has an equal and opposite reaction.

Gravity

Force pulling objects toward earth.

Force

Any push or pull applied to an object.

Torque

Rotational or twisting force around an axis.

Friction

Resistance between surfaces in contact.

Anthropometry

Body measurements and proportions affecting movement.

Buoyancy

Upward force from a fluid opposing weight.

Drag

Resistance opposing motion through a fluid.

Lift

Upward force produced by movement through fluid.

Balance

All forces equal; no directional movement.

Base of Support

Area under body supporting balance.

Center of Gravity

Point where body mass is balanced.

Scalar

Quantity with magnitude only (speed, distance).

Vector

Quantity with magnitude and direction (velocity, acceleration).

Mechanical Loading Forces

External forces acting on tissues.

Unloaded

Minimal or no external force.

Tension

Pulling force along length of structure.

Compression (Axial Load)

Pushing force that shortens structure.

Shear

Opposing parallel forces.

Bending

Combination of tension and compression.

Torsion

Twisting force around an axis.

Combined Loading

Multiple forces acting together (often torsion + compression).

All or None Principle

Muscle fibers contract fully or not at all.

All or None Application 1

One nerve can serve many muscle fibers (innervation ratio).

All or None Application 2

Force increases by recruiting more motor units.

All or None Application 3

Endurance increases by longer motor unit activation.

Ideal Mechanical Advantage

Perfect force efficiency; limited in reality by gravity and friction.