Chapter 1: Common Measurements

Metric System

• Standard system of measurement used by scientists

• Used to express mass, length, and volume

System International (SI) Units

• Standardized units of measurement

Common metric system prefixes

• Kilo - one thousand

• Centi - one hundredth

• Milli - one thousandth

Important SI Units

• Kilogram, meter, seconds, Newtons, joule, watt, meters per scan, newton-meter

Definition of Work

• Work = force x distance

• SI Unit is Newtons

• J = N x m

Common Units used to Express Work and Energy

Definition of Power

• How much work is accomplished per unit of time

• Work / Time

• Force x Velocity

• SI Unit is Watt

Common Terms and Units Used to Express Power

Measurement of Work and Power

Ergometry

• Measurement of work output

Ergometer

• Device sued to measure work

• Ex. Bench step ergometer, cycle ergometer, arm ergometer, treadmill

Cycle Ergometer-Calculation of Work and Power

Stationary cycle that allows accurate measurement of work performed

Treadmill-Calculation of Work

• Calculation of work performed while a subject runs or walks on a treadmill is not generally possible when the treadmill is horizontal

• Calculation or work performed while a subject runs or walks on a treadmill is difficult

• It is technically challenging to measure cuticle distance traveled when treadmill belt is horizontal

• Solution: increase the incline slope of treadmill

Direct Calorimetry

• Measurement of heat production as an indication of metabolic rate

• Energy expenditure commonly measure in calories

Indirect Calorimetry

• Measurement of oxygen consumption as an estimate or resting metabolic rate

• Foodstuffs + O2 -> Heat + CO2 + H2O

• Open-Circuit Spirometry: Determines VO2 by measuring amount of O2 consumed

Metabolic Equivalent (MET)

• Resting metabolic rate

• Taken as 3.5 ml•kg•min-1

• Ex. 2 MET = 7.0 ml•kg•min-1

• Expressed in the units of MET

Estimation of Energy expenditure

• Can be estimated using many types of physical activity using METS

Relationship between walking or running speed and VO2

Estimation of the O2 Requirement of Treadmill Walking

• y=mx+b

• y=0.1

Estimation of the O2 Requirement of Treadmill Running

• y=mx+b

• y=0.2

Relationship between work rate and VO2 for cycling

Comprised of 3 Components

• Resting VO2: 3.5 ml•kg•min-1

• VO2 for unloaded cycling: 3.5 ml•kg•min-1

• VO2 of cycling against external load: 1.8 ml•kg•min-1

ALWAYS GOING TO HAVE RESING AND UNLOADED

Definition of Exercise Efficiency

• Exercise efficiency = ratio of work output to energy input

• A more efficient individual uses less energy to perform the same amount of work

• Several methods to compute exercise efficiency

Calculation of net efficiency

• Net Efficiency: Ratio of work output divided by energy expended above rest

• % Net Efficiency = Work output/Energy expended (above rest) x 100

• Net efficiency of cycle ergometry often ranges form 15 - 27%

Factors that Impact efficiency

Exercise Intensity

• Curvilinear relationship between work rate and energy expenditure

• Therefore, efficiency decreases at high exercise intensities because of the higher energy cost of very heavy exercise

Speed of Movement

• There is an optimum speed of movement and any deviation reduce efficiency

Muscle Fiber Type

• Slow muscle fibers are more efficient in using ATP compared to fast muscle fibers

Definition of Running Economy and what affects it

• Oxygen cost (that is energy expenditure) of running at a specific speed.

• Lower VO2 (ml kg-1 min-1) at same speed indicates better running economy.

• Slow muscle fibers are more efficient in using ATP compared to fast

• Individual differences