Basic Biomechanical Factors and ConceptsAnatomy and Physiology of Human Movement420:050

OutlineIntroductionLeversAnatomical LeversLaws of Motion

BiomechanicsBiomechanics - study of the mechanics as it relates to the functional and anatomical analysis of biological systems and especially humansNecessary to study the bodys mechanical characteristics & principles to understand its movements

BiomechanicsMechanics - study of physical actions of forcesMechanics is divided into:Statics Dynamics

BiomechanicsStatics - study of systems that are in a constant state of motion, whether at rest with no motion or moving at a constant velocity without accelerationStatics involves all forces acting on the body being in balance resulting in the body being in equilibriumDynamics - study of systems in motion with accelerationA system in acceleration is unbalanced due to unequal forces acting on the body

BiomechanicsKinematics & kineticsKinematics - description of motion and includes consideration of time, displacement, velocity, acceleration, and space factors of a systems motionKinetics - study of forces associated with the motion of a bodyMechanical advantageLoad/effort or load divided by effortIdeally using a relatively small force, or effort to move a much greater resistance

OutlineIntroductionLeversAnatomical LeversLaws of Motion

Introduction to LeversLever: Simple machine that operates according to principle of torquesTorque: The turning effect of a forceT = Fd

FdHow can you change torque?1. Change F2. Change d3. Change direction of F

FdOptimal direction = 90 degrees

Function of LeversTwo functions:1. Force2. Speed/ROM

Function of LeversForceExamples?Common traits?Rigid barFixed pointLever movement vs. resistance movement

FR

Function of LeversSpeed/ROMExamples?Common traits?Rigid barFixed pointLever movement vs. resistance movement

FR

Components of a Lever SystemLever: Rigid barFulcrum: Axis of rotation/fixed pointForce:Applied force (F)Resistance force (R)Moment arm: dApplied forceResistance

More ConceptsMechanical advantageLevers designed for forceMechanical disadvantageLevers designed for speed/ROM

FRMechanical advantage or disadvantage?How does mechanical advantage affect movement of the lever?

Advantage: Small effort moves big resistanceDisadvantage: Big movement required to move resistance a small distance

Human Application?Lever?Bones (Not always a bar)Fulcrum?JointsApplied force?MusclesResistance force?Weight of limb, external resistance

Classification of LeversLever classification based on the relative location of:1. Axis of rotation/fulcrum (A)2. Resistance force (R)3. Applied force (F)

A R F

First Class LeverCenter: (A) Axis of rotation/fulcrumMechanical advantageMechanical disadvantageExamplesCrow barSeesaw

Advantage or disadvantage?

Second Class LeverCenter: (R) Resistance forceMechanical advantageAlwaysMechanical disadvantageNeverExamplesWheelbarrowNutcracker

Third Class LeverCenter: (F) Applied forceMechanical advantageNeverMechanical disadvantageAlwaysExamplesRowingShovelingBat, tennis racket

Baseball, tennis?

Human ApplicationFirst class leverElbow extension against a resistance

(A) Axis of rotation/fulcrum(F) Applied force(R) Resistance forceMechanical advantage or disadvantage

Human ApplicationSecond class leverAnkle plantar flexion

Mechanical advantage or disadvantage?Not many in the body

Human ApplicationThird class leverElbow flexion

Mechanical advantage or disadvantage?Many of these in body

In general, is the human body built for force application or speed/ROM?