Lectures 31: Metabolism and Breathing

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Lectures 31 Metabolism and Breathing
Readings Chapanis (1996, chapter 5)
Acknowledgement In addition to the Chapanis
text, portions of this lecture were extracted
from Other Ergonomics texts
09/10/99
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Questions to be addressed

• What is the relationship between oxygen uptake,
  burning of energy
• (digestion and use of the energy in food),
• and blood flow
• (heart rate)?
• What factors affect the energy balance of the
  body?

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Introduction

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

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Nervous System

• Central Nervous System
• Peripheral Nervous System
• Autonomic Nervous System

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Central Nervous System

• includes the brain and spinal cord
• receives information from our various senses,
• transmits it to the central nervous system for
  control and decision-making

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Peripheral Nervous System

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

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Respiratory System

• It provides oxygen for energy metabolism
• It dissipates the by-products of metabolic action
  

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Circulatory Systems

• 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.

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Energy Balance Equation

• I M W S
• where
• I energy supplied to the body by food or
  drink
• M metabolic energy
• W work performance
• S energy store in the body

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Significance of work physiology

• Safety health
• Methods evaluation
• Job evaluation
• Rest scheduling
• Job specification
• Employee selection

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Metabolism

• Definition
• Transformation chemical energy
  work
• Units of Measurement
• kilocalorie (kcal)
• 1 kcal 1000 cal 1 Cal
• heat required to raise 1 liter H2O
• 15 C 16 C

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Metabolism (1)
glycolysis
glucose
pyruvic acid
carbohydrates
oxidation
fatty acids
acetic acid
fats
deamination
amino acids
deaminated AAs
proteins
digestion
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Metabolism (2)
glycolysis
glucose
pyruvic acid
carbohydrates
oxidation
fatty acids
acetic acid
fats
deamination
amino acids
deaminated AAs
proteins
digestion
CO2
energy
H2O
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Metabolism (3)
glycolysis
glucose
pyruvic acid
carbohydrates
oxidation
fatty acids
acetic acid
fats
deamination
amino acids
deaminated AAs
proteins
digestion
CO2
energy
adenosine triphosphate
H2O
adenosine diphosphate PO4
creatine phosphate
creatine PO4
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Metabolism - Components

• Total Metabolism
• Basal Metabolism (life support)
• Activity Metabolism (work, leisure)

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Basal Metabolism

• Male ( 70 kg ) 1700 kcal/day _at_ 1.2 kcal/min
• Female ( 60 kg ) 1400 kcal/day _at_ 1.0 kcal/min
• Factors
• Sex
• Size
• Age

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Maximum Aerobic Power (MAP)

• Factors affecting MAP
• Age
• Sex
• Heredity
• Physical conditioning

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Factors Affecting Energy Expenditure

• Rate of work
• Posture of body
• Method of work

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Measurement

• O2 uptake
• Respiration rate ( vital capacity)
• Heart rate
• Activity standards

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Oxygen Usage

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

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Applications of Work Physiology

• Calculate rough energy balance
• Measure physical workload
• Adjust physical demands of work as necessary

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Questions and Exercises

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