This lecture discusses metabolism and breathing. It addresses the relationship between oxygen uptake, energy from food, and blood flow. The lecture introduces metabolism and the respiratory, circulatory, nervous systems. It covers factors that affect energy balance and expenditure like rate of work, posture, and method of work. Measurement of oxygen usage, heart rate and applications to work physiology are also summarized.

1. 09/10/99
LLeeccttuurreess 3311:: MMeettaabboolliissmm aanndd
BBrreeaatthhiinngg
Readings: Chapanis (1996, chapter 5)
Acknowledgement: In addition to the Chapanis text,
portions of this lecture were extracted from
Other Ergonomics texts

2. QQuueessttiioonnss ttoo bbee aaddddrreesssseedd
l What is the relationship between oxygen
uptake, burning of energy
– (digestion and use of the energy in food),
l and blood flow
– (heart rate)?
l What factors affect the energy balance of the
body?

3. IInnttrroodduuccttiioonn
l Breathing and Metabolism are basic functions
that allow us to survive.
l We need to design tasks that are not too
physically demanding, and that have enough
rest breaks built into them.
l Biochemistry of metabolism is well understood,
but beyond the scope of this course (addressed
in third year)

4. NNeerrvvoouuss SSyysstteemm
l Central Nervous System
l Peripheral Nervous System
l Autonomic Nervous System

5. CCeennttrraall NNeerrvvoouuss SSyysstteemm
l includes the brain and spinal cord
l receives information from our various senses,
l transmits it to the central nervous system for
control and decision-making

6. PPeerriipphheerraall NNeerrvvoouuss SSyysstteemm
l includes the cranial and spinal nerves
l regulates involuntary functions of
– cardiac muscles, blood vessels, digestion, and
glucose release by the liver
l is responsible for the "flight, fright, or fight”
reactions that we experience in emergency or
dangerous situations

7. RReessppiirraattoorryy SSyysstteemm
l It provides oxygen for energy metabolism
l It dissipates the by-products of metabolic action

8. CCiirrccuullaattoorryy SSyysstteemmss
l The main circulatory system
– consists of the blood vessels and capillaries that
are richly distributed throughout the human body.
– provides the means by which these products are
transported between lungs, hearts, muscles, and
other body cells.

9. EEnneerrggyy BBaallaannccee EEqquuaattiioonn
l I = M + W + S
l where
l
l I = energy supplied to the body by food or drink
l M = metabolic energy
l W = work performance
l S = energy store in the body

10. SSiiggnniiffiiccaannccee ooff ““wwoorrkk pphhyyssiioollooggyy
l Safety & health
l Methods evaluation
l Job evaluation
l Rest scheduling
l Job specification
l Employee selection

11. MMeettaabboolliissmm
l Definition
– Transformation: chemical energy work
l
– kilocalorie (kcal)
– 1 kcal = 1000 cal = 1 Cal
= heat required to raise 1 liter H2O
15 °C 16 °C

12. MMeettaabboolliissmm ((1))
carbohydrates
fats
proteins
glucose
fatty acids
amino acids
pyruvic acid
acetic acid
deaminated AAs
glycolysis
oxidation
deamination
digestion

13. MMeettaabboolliissmm ((22))
carbohydrates
fats
proteins
glucose
fatty acids
amino acids
pyruvic acid
acetic acid
deaminated AAs
glycolysis
oxidation
deamination
digestion
CO2
H2O
energy

14. MMeettaabboolliissmm ((33))
carbohydrates
fats
proteins
glucose
fatty acids
amino acids
pyruvic acid
acetic acid
deaminated AAs
glycolysis
oxidation
deamination
digestion
CO2
H2O
energy
adenosine triphosphate
adenosine diphosphate + PO4
creatine + PO4 creatine phosphate

15. MMeettaabboolliissmm -- CCoommppoonneennttss
Total Metabolism =
Basal Metabolism (life support)
+
Activity Metabolism (work, leisure)

16. BBaassaall MMeettaabboolliissmm
l Male ( 70 kg ): 1700 kcal/day @ 1.2 kcal/min
l Female ( 60 kg ): 1400 kcal/day @ 1.0 kcal/min
l Factors:
– Sex
– Size
– Age

17. MMaaxxiimmuumm AAeerroobbiicc PPoowweerr ((MMAAPP))
Factors affecting
MAP
l Age
l Sex
l Heredity
l Physical
conditioning

18. FFaaccttoorrss AAffffeeccttiinngg EEnneerrggyy
EExxppeennddiittuurree
l Rate of work
l Posture of body
l Method of work

19. MMeeaassuurreemmeenntt
l O2 uptake
l Respiration rate (+ vital capacity)
l Heart rate
l Activity standards

20. OOxxyyggeenn UUssaaggee
l People are biologically adapted to breathing air
that contain 21% oxygen by volume at sea
level.
l Too little oxygen (hypoxia) induces sleepiness,
headache, inability to perform simple tasks
l In the extreme lack of oxygen leads to loss of
consciousness and death.

21. AApppplliiccaattiioonnss ooff WWoorrkk PPhhyyssiioollooggyy
l Calculate rough energy balance
l Measure physical workload
l Adjust physical demands of work as necessary

22. QQuueessttiioonnss aanndd EExxeerrcciisseess
l Why does oxygen uptake tend to increase
when heart rate increases?
l Why does the body need oxygen?
l Why does dieting sometimes make it more
difficult to lose weight in the future?
l What is a comfort zone and why should we be
designing for it?