Kinetic Concepts for Analyzing Human Motion

Presentation Created by

Dr. Hazrat Bilal Malakandi. PTDPT (IPM&R, KMU)

Objectives

• Identify common units of measurement for mass, force, weight, pressure, volume, density, specific weight, torque, and impulse

• Identify and describe the different types of mechanical loads that act on the human body

• Identify and describe the available instrumentation for measuring kinetic quantities

• Solve quantitative problem involving vector quantities using both graphic and trigonometric procedures

Basic Concepts Related to Kinetics

• Inertia

• Mass

• Force

• Center of Gravity

• Weight

• Pressure

• Volume

• Density

• Specific weight

• Torque

• Impulse

Common Units for Kinetic Quantities

Quantity Symbol Metric Unit English Unit

Mass m kg slug

Force F N lb

Pressure P Pa psi

Volume (solids) V m3 ft3

(liquids) liter gallon

Density kg/m3 lb/ft3

Specific weight N/m3 lb/ft3

Torque T N-m ft-lb

Impulse N • s lb • s

Mechanical Loads on the Human Body

• Compression • Tension• Shear• Stress• Torsion• Bending• Combined loading

The Effects of Loading

• Deformation

When an external force is applied to the human body, several factors influence whether an injury occurs– Magnitude and direction of force– Area over which force is distributed– Load-deformation curve– Yield point (elastic limit)– Failure

Repetitive vs. Acute Loads

• Repetitive loading• Acute loading• Macrotrauma• Microtrauma

Tools for Measuring Kinetic Quantities

• Electromyography (EMG)– To study neuromuscular function

• Dynamography– Primarily employed in gait research– Starts, takeoffs, landings, baseball & golf

swings, and balance

Vector Algebra

• Vector• Kinetic vector quantities

– force weight, pressure, specific weight & torque

• Kinematic vector quantities– Displacement, velocity & acceleration

• Scalar quantities– Mass, volume, length & speed

Vector Resolution

Vertical

Horizontal

Example: A ball is thrown into the air