Basic Biomechanical Factors and Concepts Anatomy and Physiology

Basic Biomechanical Factors and Concepts Anatomy and Physiology of Human Movement 420: 050 1

Outline l l Levers Anatomical Levers 2

Outline l l Levers Anatomical Levers 3

Introduction to Levers l l Lever: Simple machine that operates according to principle of torques Torque: The turning effect of a force T = Fd 4

d How can you change torque? 1. Change F 2. Change d 3. Change direction of F F 5

d Optimal direction = 90 degrees F 6

Function of Levers l Two functions: 1. Force 2. Speed/ROM 7

Function of Levers l Force l l Examples? Common traits? l l l Rigid bar Fixed point Lever movement vs. resistance movement 8

F R 9

Function of Levers l Speed/ROM l l Examples? Common traits? l l l Rigid bar Fixed point Lever movement vs. resistance movement 10

F R 11

Components of a Lever System l l l Lever: Rigid bar Fulcrum: Axis of rotation/fixed point Force: l l l Applied force (F) Resistance force (R) Moment arm: d l l Applied force Resistance 12

More Concepts l Mechanical advantage l l Levers designed force Mechanical disadvantage l Levers designed for speed/ROM 13

F R Mechanical advantage or disadvantage? How does mechanical advantage affect movement of the lever? 14

Advantage: Small effort moves big resistance Disadvantage: Big movement required to move resistance a small distance 15

Human Application? l l Lever? Bones (Not always a bar) Fulcrum? Joints Applied force? Muscles Resistance force? Weight of limb, external resistance 16

Classification of Levers l Lever classification based on the relative location of: 1. Axis of rotation/fulcrum (A) 2. Resistance force (R) 3. Applied force (F) ARF 17

First Class Lever l l Center: (A) – Axis of rotation/fulcrum Mechanical advantage Mechanical disadvantage Examples Crow bar Seesaw 18

19 Advantage or disadvantage?

Second Class Lever l l Center: (R) – Resistance force Mechanical advantage l l Mechanical disadvantage l l Always Never Examples Wheelbarrow Nutcracker 20

21

Third Class Lever l l Center: (F) – Applied force Mechanical advantage l l Mechanical disadvantage l l Never Always Examples Rowing Shoveling Bat, tennis racket 22

Baseball, tennis? 23

Human Application l First class lever l Elbow extension against a resistance 24

Mechanical advantage or disadvantage (R) – Resistance force (F) – Applied force (A) – Axis of rotation/fulcrum 25

Human Application l Second class lever l Ankle plantar flexion 26

Mechanical advantage or disadvantage? Not many in the body 27

Human Application l Third class lever l Elbow flexion 28

Mechanical advantage or disadvantage? Many of these in body 29

In general, is the human body built force application or speed/ROM? 30