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Chapter 3
Lecture Slides
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Measures of Energy
What is energy?
• Forms of energy
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Mechanical
Chemical
Heat
Electrical
Light
Nuclear
• For sport purposes, mechanical, chemical and heat
energy are most important.
Figure 3.1
Human energy
• Mechanical energy
– Capacity to do metabolic work
• Chemical energy
– Storage form of energy
• Heat energy
– Product of metabolism
How do we measure work, physical
activity, and energy expenditure
• Work and power
– Work = force x distance
– Power = work/time
• Measurement systems
– English
– Metric
– International (SI)
Energy measurement systems
Work and power measurement
Measurement of work and physical activity
• Ergometer to measure work output
– Cycle
– Arm
• Devices to measure physical activity
– Pedometer
– Accelerometer
– Intelligent Device for Energy Expenditure and
Activity
– Global Positioning Systems
Measurement of energy expenditure
• Measurement of work is not the same as
measurement of energy expenditure
– Isometric muscle contraction; no work produced
• Calorimetry measures energy expenditure
– Direct calorimetry
– Indirect calorimetry
Direct calorimetry
Direct calorimetry
Indirect calorimetry
Indirect calorimetry
• Laboratory conditions
– Measurement of oxygen uptake and carbon dioxide
production
• Real life conditions
– Doubly labeled water technique
• Stable isotopes of hydrogen and oxygen are ingested
• Analysis of urine and blood for hydrogen and oxygen to measure
carbon dioxide fluctuation
What is the most commonly used
measure of energy?
• In the United States, the Calorie. In most of the
world, the joule.
• 1 gram calorie will increase the temperature of 1
gram of water 1 degree Celsius
• 1000 gram calories = 1 kilocalorie
• We shall use the kilocalorie, capitalized as Calorie or
as C, as the most common measure of energy in this
text.
Calories in food
The Calories in 8 ounces of orange juice provides
enough energy for the average male to run a mile.
Human Energy Systems
• Energy systems for muscular activity in the
human body are designed to produce energy
for work at varying rates.
How is energy stored in the body?
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Adenosinetriphosphate (ATP)
Phosphocreatine (PCr)
Carbohydrate
Fat
Protein
Energy for metabolic activity
• ATP is the immediate source of energy for metabolic
activity, including muscle contraction
• PCr can regenerate ATP rapidly
• Both ATP and PCr are in very short supply
• Carbohydrate, fat and protein can be metabolized to
produce ATP and PCr
Figure 3.6
Major energy stores in the human body
What are the human energy systems?
Predominant energy systems in runners
Anaerobic power (ATP-PCr)
60-200 meters (6-20 seconds)
Anaerobic capacity (anaerobic glycolysis; lactic acid)
400-800 meters (43-103 seconds)
Aerobic power (aerobic glycolysis)
5,000-10,000 meters (12-26 minutes)
Aerobic capacity (aerobic lipolysis)
42.2-100 kilometers (125-360 minutes)
The ATP-PCr energy system
The ATP-PCr energy system
The lactic acid energy system
(anaerobic glycolysis)
Glycolysis
The oxygen energy system
• Aerobic glycolysis
– Oxidation of glycogen or glucose
• Aerobic lipolysis
– Oxidation of fatty acids
• Aerobic proteolysis (limited energy production)
– Oxidation of glucogenic or ketogenic amino acids
Figure 3.10
Figure 3.11
Figure 3.12
Conversion of pyruvate to acetyl CoA
Mitochondria oxidation
Energy pathways for fatty acids
Amino acids and the Krebs cycle
What nutrients are necessary for the
operation of the human energy systems?
• Water
– Hydrolysis
• Vitamins
– B vitamins, as coenzymes, are involved in many energy
processes
• Minerals
– Minerals, as metalloenzymes, are also involved in energy
processes; iron is part of hemoglobin to transport oxygen
• Dietary supplements
– Carnitine, coenzyme Q10 and others marketed to athletes
Human Energy Metabolism during Rest
What is metabolism?
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ENERGY TERMINOLOGY
Basal Metabolic Rate (BMR) – Resting; post-absorptive
Maintain basal metabolism
Only sleeping metabolism is lower
Basal Energy Expenditure (BEE)
BMR extrapolated over 24 hours
Resting Metabolic Rate (RMR)
BMR + small amounts due to prior activity
Resting Energy Expenditure (REE)
RMR extrapolated over 24 hours
Thermic Effect of food (TEF)
Also known as Dietary Induced Thermogenesis (DIT)
Post-meal elevation in RMR due to digestive processes
Thermic Effect of Exercise (TEE)
Also known as Exercise Metabolic Rate (EMR)
Increase in metabolic rate associated with exercise
Metabolic aftereffects of exercise
Total Daily Energy Expenditure (TDEE)
Sum of BEE (REE), TEE, and TDEE
Human Energy Metabolism during Rest
What is metabolism?
• Metabolism represents the sum total of all physical
and chemical changes that take place within the
body.
• Anabolic metabolism (anabolism)
– Constructive processes
• Catabolic metabolism (catabolism)
– Disintegration processes
Metabolism
• Total Daily Energy Expenditure (TDEE)
– Basal and resting energy expenditure
– Thermic effect of food
– Thermic effect of exercise
What factors account for the amount of energy
expended during rest?
• Basal metabolism
– Basal metabolic rate (BMR)
• Energy needed to stay alive when awake
• Only sleeping metabolic rate is lower
– Basal energy expenditure (BEE)
• Basal metabolism over 24-hour period
• Resting metabolism
– Resting metabolic rate (RMR)
• BMR plus small amounts associated with eating, prior activity
• About 10 percent higher than BMR
– Resting energy expenditure (REE)
• Resting metabolism over 24 hour period
What effect does eating a meal have on
the metabolic rate?
• Metabolic rate is elevated after a meal
– Specific dynamic action’
– Dietary-induced thermogenesis
– Thermic effect of food (TEF)
• TEF is expressed as the % of meal energy content
– 5-10% for a mixed meal
– TEF may be a consideration in some weight-control diets
How can I estimate my
daily resting energy expenditure
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Estimate not as accurate as BMR test
May be useful for weight control programs
Other methods include effects of daily activity
Simple methods to estimate RMR
– 1 Calorie/kilogram body weight per hour
– Various formulae
Estimation of RMR
Estimation of RMR
Estimation of RMR
What genetic factors affect my REE?
• Age
– Infancy through adulthood
• Gender
– Females REE about 10-15% lower
• Natural hormonal activity
• Body surface area
– Genetically lean versus stout
How does body composition
affect my REE?
• Body composition
– Muscle versus fat
• Losing body weight, both fat and muscle, lower REE
• Maintaining normal body weight while reducing
body fat and increasing muscle mass may raise REE
• Decline in REE with aging may be associated with
loss of muscle mass
What environmental factors may also
influence the REE?
• Exposure to cold weather
– Thermogenesis
• Exposure to warm or hot weather
– Sweating and cardiovascular demands
• Exposure to altitude
– Increased ventilation
• Cigarette smoking
– Nicotine
• Caffeine
– One study found increases of 10 percent
What energy sources are used during rest?
• The oxygen energy system prevails during rest
1. About 60 percent of energy from fat
– About 40 percent of energy from carbohydrate
– Small amount of energy from protein
• The diet may affect the energy source during rest
– Eating a diet rich in carbohydrate or fat will,
respectively, increase energy production from
carbohydrate and fat
Human Energy Metabolism during Exercise
• Exercise stresses most body systems
• Neuromuscular system determines the energy
system to be used during exercise
How do my muscles influence the amount
of energy I can produce during exercise
Muscle fiber types
• Three main types of muscle fibers
– Type I: Slow twitch red fiber
• Slow oxidative (SO)
– Type IIa: Fast twitch red fiber
• Fast oxidative-glycolytic (FOG)
– Type IIb (IIx): Fast twitch white fiber
• Fast glycolytic (FG)
Muscle fiber types
What effect does muscular exercise have
on the metabolic rate?
• All physical activity increases the metabolic rate
• Activities of daily living (ADL)
– NonExercise Activity Thermogenesis (NEAT)
• Planned exercise activity
– Exercise metabolic rate (EMR)
– Thermic effect of exercise (TEE)
Exercise intensity and metabolic rate
How is exercise intensity measured?
• Actual work output
– Ergometer (watts)
• Physiological cost of the activity
– ATP-PCr energy system
• Muscle biopsy
• Computerized imaging procedures
– Lactic acid energy system
• Onset of blood lactic acid (OBLA); steady-state threshold
– Oxygen energy system
• Oxygen uptake; maximal oxygen uptake (VO2max)
Figure 3.13
Figure 3.14
How is the energy expenditure of exercise
metabolism expressed?
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Calories
Kilojoules
Oxygen uptake
METS
– Multiples of the RMR
Energy expenditure
MET
1 MET = 3.5 ml O2/kg body weight/minute
CALORIE (KILOCALORIE)
Heat to raise 1 kg of water 1
1 Calorie = 4.2 kilojoules (kJ)
Energy expenditure
OXYGEN
1 MET resting oxygen uptake
3.5 ml O2 x 70 kg = 245 ml O2 per minute
1 Liter Oxygen = c. 5 Calories (kilocalories)
1 Liter Oxygen = 1000 milliliters
245/1000 = 0.245 liter oxygen per minute @ 1 MET
0.245 L x 5 Calories/L = 1.225 Calories/minute
Exercise energy equivalencies
How can I tell what my metabolic rate is
during exercise?
• Oxygen consumption is precise, but not very
practical
• Other physiological measures
– Heart rate
– Respiratory rate
Figure 3.16
How can I determine the energy cost of
exercise?
• Consult appendix B.
What are the best types of activities to
increase energy expenditure?
• Activities involving large muscle groups
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Walking
Running
Cycling
Aerobic dance
Home exercise equipment
Resistance or strength training (lower than aerobic)
• Intensity and duration
Physical activities to increase
energy expenditure
Walking and running
• Walking:
– About 1 Calorie/kg body weight/mile or 0.45
Calorie/lb/mile @ 2-4 mph
• Running:
– About 1.6 Calories/kg bodyweight/mile or 0.73
Calorie/lb/mile
Cool Website
www.MyPyramid.gov
• Go to MyTracker to calculate the energy cost of your
daily physical activities.
Does exercise affect my resting energy
expenditure (REE)?
• Metabolic aftereffects of exercise
– Excess postexercise oxygen consumption (EPOC)
• RMR remains elevated after intense exercise
– % increase in RMR varies, but normally about 4-16%
– Time of elevated RMR varies
– Total number of Calories is relatively low; < 30
Does exercise affect the thermic effect of
food (TEF).
• Research finding are ambiguous
• An effect, if any, is believed to be minor
How much energy do I need to consume
daily?
• Estimated Energy Expenditure (EER)
– Total Daily Energy Expenditure (TDEE)
• Basal energy expenditure (BEE)
• Thermic effect of food (TEF)
• Thermic effect of exercise (TEE)
Total Daily Energy Expenditure
Estimated Energy Requirement (EER)
• Defined as the dietary energy intake needed to
maintain weight in a healthy adult
• A key factor is the Physical Activity Level (PAL),
which is the TDEE divided by the BEE. The PAL is
used to determine the Physical Activity (PA)
coefficient
Estimated Energy Requirement
Males (19 years and older)
662 – 9.53 x age + [PA x (15.91 x weight + 539.6 x height)
Females (19 years and older)
354 – 6.91 x age + [PA x (9.361 x weight + 726 x height)
Age:
Weight:
Height:
PA:
In years
In kilograms
(Conversion: Multiply pounds by 0.454
In meters
(Conversion: Multiple inches by 0.0254)
Based on the Physical Activity Level (PAL)
Physical Activity Level (PAL)
Institute of Medicine bases the PAL on the amount of
daily physical activity that is the equivalent of
walking at a pace of 3-4 MPH, or 15-20 minutes per
mile
– Low Active (PAL 1.5): Walk 2.2 miles
– Active (PAL 1.75): Walk 7 miles
– Very Active (PAL 2.2): Walk 17 miles
You need not actually walk this amount, but do other
physical activities that are the equivalent of walking
a mile, such as using an elliptical trainer for 12-15
minutes
Sedentary and very active females
22 years old; 132 lbs (60 kg); 55 inches (1.4 m)
Human Energy Systems and
Fatigue during Exercise
What energy systems are
used during exercise?
• Intensity is the most important factor determining
which energy system is used during exercise
• Most exercise tasks use a blend of the three major
human energy systems, but use of one system will
predominate depending on exercise intensity
Predominant energy systems in runners
Anaerobic power (ATP-PCr)
60-200 meters (6-20 seconds)
Anaerobic endurance (anaerobic glycolysis; lactic acid)
400-800 meters (43-103 seconds)
Aerobic power (aerobic glycolysis)
5,000-10,000 meters (12-26 minutes)
Aerobic endurance (aerobic lipolysis)
42.2-100 kilometers (125-360 minutes)
Major characteristics of the
human energy systems
Percentage contribution from aerobic and anaerobic
energy sources during different time periods of
maximal work
Aerobic energy system
29% of energy in 200-meter dash
84% of energy in 1500-meter run
Spencer and Gastin
What energy sources are used
during exercise?
• ATP-PCr energy system
– Adenosinetriphosphate
– Phosphocreatine
• Lactic acid energy system
– Muscle glycogen (carbohydrate)
• Oxygen energy system
– Muscle glycogen and blood glucose (carbohydrate)
– Muscle triglycerides and blood FFA (fat)
– Protein (amino acids); minor source of energy
Energy sources during exercise
• Carbohydrate versus fat
– Blood glucose and blood FFA during mild exercise; less
than 50% VO2max
– Muscle glycogen and muscle triglycerides at higher
intensity
• The crossover concept
– Fat is major energy source at low-intensity exercise
– Carbohydrate becomes major energy source at higherintensity levels
• Training increases ability to use both fat and carbohydrate
• Elite marathon runners may need 4-5 grams per minute
What is fatigue?
• Fatigue may be chronic or acute
Chronic fatigue
• Overreaching
– May impair performance
– Planned phase of training
• Overtraining
– Prolonged periods of fatigue
• Chronic fatigue syndrome
– Genuine medical condition
• Disturbances of immune system
• Infections
• Mental stress
Acute fatigue
• Acute fatigue may be defined as the inability to
continue exercising at a desired level of intensity.
• The site of fatigue
– Peripheral
– Central
Possible sites of fatigue
What causes fatigue in athletes?
• Peripheral versus central fatigue
• The current thinking is that acute fatigue during
exercise is associated with an interaction between
peripheral and central factors
• Central factors (brain) make the decision to reduce
power output
• Peripheral factors (muscles, blood) may influence
the brain
How can I delay the onset of fatigue?
• Proper sport training is the most effective means to
delay the onset of fatigue
– Physiological training
• Train specific energy systems
– Psychological training
• Train for mental strength
– Biomechanical training
• Improve biomechanical skills for energy economy
• Nutrition is also important to help delay fatigue
How is nutrition related
to fatigue processes?
• Nutritional strategies have been used to help
delay or prevent the development of fatigue
during exercise using all human energy
systems
Examples of some nutritional strategies and,
theoretically, how they delay fatigue
Examples of some nutritional strategies and,
theoretically, how they delay fatigue
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