This document discusses different methods of measuring work, power, and energy expenditure during exercise. It describes common units of measurement like joules and watts. Examples are provided for calculating work and power output during activities like weight lifting, stepping on a bench, and cycling. Measuring work and power can provide important information for coaches, athletes, and exercise specialists.

1. Measurment Of work,
Power, Energy,
Expenditure

2. • Measurement of energy expenditure and power
output has many applications in exercise science.
• For example, adequate knowledge of the energy
requirements of physical activities (e.g., running)
is important to a coach in planning a training and
dietary program for athletes.

3. • This same information can be used by an exercise
specialist to prescribe exercise for adults entering
a fitness program.
• Therefore, an understanding of human energy
expenditure, how it is measured, and its practical
significance is critical for the physical therapist,
coach, physical educator, exercise specialist, or
exercise physiologist.

4. UNITS OF MEASURE
MATRIC SYSTEM:
•Is the standard system of measurement for
scientists and is used by almost all scientific
journals .
•In the metric system, the basic units of length,
volume, and mass are the meter, the liter, and the
gram, respectively

6. S.I UNITS:
•A uniform system of reporting scientific
measurement has been developed through
international cooperation.
•This system, known as System International units,
or SI units, has been endorsed by almost all
exercise and sports medicine journals for the
publication of research data

8. WORK AND POWER
• Work:
• Work is defined as the product of force multiplied
by distance.
Work = force X distance
• The SI unit for force is …….. (N), whereas
• The SI unit for distance is …………….(m)

9. • Consider the following example to compute
work during a weight-lifting exercise.
• If you lifted a 10-kilogram (Kg) weight
upward over the distance of two meters (m),
the work performed would be:
Work = 97.9 N X 2 m
= 195.8 Joules

10. • The computation of work in SI units required
a conversion of Kg to N.
• To obtain the force in N, we converted the 10
Kg to N using the conversion factor
contained in table
(ie, I Kg =9.79 N so 10 Kg = 97.9 N)

12. • Therefore. the work performed was
computed by : multiplying the force
(expressed in N) times the distance traveled
(expressed in m) with the resulting work
being expressed in Joules, which is the SI
unit for work (where I joule = I Nm; table )

13. Power
• Power is the term used to describe how much
work is accomplished per unit of time .
• The SI unit for power is the watt (W) and is defined
as I Joule per second
Power can be calculated as: Power = Work -;- time

14. • The concept of power is important because it
describes the rate at which work is being
performed (work rate).
• It is the work rate or power output that
describes the intensity of exercise.

15. • Any healthy adult could perform a total work
output of 20,000 joules.
• However, only a few highly trained athletes could
perform this amount of work in sixty seconds (s).
• Calculation of power output using this example
can be done as follows
Power = 20.000 Joules/60 seconds
= 333.33 watts

17. (a) A bench step.
(b) Friction-braked
cycle ergometer.
(c) Motor-driven
treadmill.
(d) Arm crank
ergometer. Arm
crank ergometry can
be used to measure
work output with the
arms.

18. MEASUREMENT OF WORK AND POWER
• The term ergometry refers to ????
• The word ergometer refers to the apparatus
or device used to measure a specific type of
work
• Many types of ergometers are in use today in
exercise physiology laboratories.

19. BENCH STEP
• One of the earliest ergometers used to measure
work capacity in humans was the bench step.
• This ergometer is still in use today and simply
involves the subject stepping up and down on a
bench at a specified rate.

21. Calculation of the work performed during bench:
•Suppose a 70-kg man steps up and down on a 50-
centimeter (05 meter) bench for ten minutes at a
rate of thirty steps per minute.
•The amount of work performed during this ten-
minute task can be computed as follows:
•Force = 685.3 N (ie, 70 Kg X 9.79 N/Kg)
•Distance = 0.5 m . step-l X 30 steps· min-1 X 10
min
= 150 m

22. • Therefore, the total work performed is
685.3 N X 150 m = 102,795 Joules
or
102.8 kilojoules

23. • The power output during this exercise can be
calculated as:
• Power can be calculated as:
Power = Work -;- time
Power = 102,795 Joules/600 seconds
171.3 watts

24. Cycle Ergometer
• The cycle ergometer was developed more than
100 years ago and remains a popular ergometer in
exercise physiology laboratories today

25. • This type of ergometer is a stationary exercise
bicycle that permits accurate measurement of the
amount of work performed.
• Distance traveled can be determined by
computing the distance covered per revolution of
the pedals (6 meters per revolution on a standard
Monark cycle) times the number of pedal
revolutions.

26. • Consider the following example for the
computation of work and power using
the cycle ergometer Calculate work
given:

27. • Duration of exercise = 10 min
• Resistance against flywheel = 1.5 kg or 14.7 N
• Distance traveled per pedal revolution = 6 m
• Pedalling speed = 60 rev' min-I
Therefore, the total revolutions in 10m in
= 10 min X 60 rev' min-I

28. • Hence,
Work = force X distance
work = 14.7 N X (6 m . rev-I X 600 rev)
= 52 ,920 Joules or 52 .9 kilojoules

29. • The power output in this example is computed by:
Power = Work -;- time
dividing the total work performed by time
Power = 52 ,920 Joules -'- 600 seconds
= 88.2 watts