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Chapter 1 – Common Measurements in Exercise Physiology
SI units
- Force – Newton (N)
- work – joule (J)
- energy – joule (J)
- power – watt (W)
- velocity – m/s
- torque – Newton-meter
Work and Power Defined
Work – product of force and the distance through which that force acts
Work (J) = Force (N) x Distance (m)
Power – how much work is accomplished per unit of time; rate at which work is performed
Power (W) = work (J) / time (s)
power and work require that a force is moved against some resistance
Types of Ergometers
ergometry – measurement of work output
ergometer – device used to measure a specific type of work
bench step, cycle ergometer, arm ergometer, treadmill
Measurement of Work and Power
cycle ergometer: work = resistance x (6m/rev x # of revs); power = work/time
treadmill: work = treadmill speed x (% grade / 100) x exercise time
Measurement of Energy Expenditure
2 techniques to measure human energy expenditure: direct and indirect calorimetry
Direct calorimetry: measuring heat production of a person provides a direct measurement of
metabolic rate, J or kcal
Indirect calorimetry: measuring O2 consumption provides an estimate of metabolic rate, open-
circuit spirometry
Common Expressions of Oxygen Consumption and Energy Expenditure
- absolute or relative to body weight
- VO2 (L/min)
oL/min x (inspired – expired)
- kcal/min
- VO2 (ml/kg/min)
- METs
oVO2ml/kg/min / 3.5ml/kg/min
o1 MET = 3.5ml/kg/min
- METs are a tool to define both intensity and volume of exercise
o1 MET = resting
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Ch 1 - notes from the ch 1 of the book; common measurements in exercise …
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omoderate PA = 3-6 METS
ovigorous PA = more than 6 METS
owidely used to describe how much moderate intensity PA is performed each
week
Estimation of Energy Expenditure
- O2 cost = VO2 at steady state
- the relationship between speed and VO2 cost is linear for both walking and running
- the energy cost of a horizontal treadmill walking or running and cycling can be estimated
with reasonable accuracy because the O2 requirements increase as a linear function of
speed and power
Calculation of Exercise Efficiency
- exercise efficiency: ratio of work output to energy input during PA
- more efficient individual uses less energy to do the same amount of work
- net efficiency – ratio of work output divided by the energy expended above rest
Factors that influence exercise efficiency
1) the exercise work rate
a. efficiency decreases as work rate increases
2) the speed of movement
a. there is an optimum speed of movement for any given work rate
3) the fiber composition of the muscles performing the exercise
a. exercise efficiency is greater in subjects who possess a high percentage of slow
muscle fibers compared to subjects with a high percentage of fast fibers
b. slow muscle fibers are more efficient than fast fibers
Running Economy
- the measurement of O2 at any given speed offers a measure of running economy
- running economy is better in elite runners compared to those with less ability or
untrained runners
- considerable variation in running economy between individuals, independent of running
ability
