Transcript Part B: Energy for Movement

Metabolic System Unit
Metabolism, Energy and
the Basic Energy Systems
Chapters 2, 3, and 4
Metabolism
 1. Metabolism
 energy transfer
 1st Law of Thermodynamics
 ATP
 2. By-products of metabolism
 Heat, CO2 and biologic work
Energy
1. 60% to 70% of the energy in the human body is degraded to
heat.
 The remainder is used for mechanical work and cellular
activities.
Energy
2. The energy we derive from food is stored in a high-energy
compound - ATP.
Energy
3. CHO provides about 4.1 kcal of energy per gram, compared
to about 9 kcal per gram for fat.
 CHO energy is most accessible.
We use CHO in the form of glucose.
CHO
grams
 Liver glycogen
 Muscle glycogen
 Glucose in body fluids
Total
110
500
15
625
kcal
451
2,050
62___
2,563
We use fat in the form of triglyceride
(3 fatty acids and 1 glycerol).
Fat
 Subcutaneous
 Intramuscular
Total
grams
kcal
7,800
161
7,961
70,980
1,465
72,445
Protein
 Protein can also provide energy (4.1 kcal per gram).
We use protein in the form of amino
acids.
Energy
5. One kcal equals the amount of heat energy needed to raise 1
kg of water 1 degree C from 14.5 to 15.5 degrees C.
Predominant Energy Pathways
 We expend
approximately 100 kCal
per mile walked or
jogged
Definitions
 Anaerobic – literally means “without oxygen”
 On a local level this might be true
 Might be better to think in terms of “hypoxic” which means “too
little oxygen”.
Definitions
 Aerobic – means “with oxygen”
 Both terms relate to energy metabolism or how we transfer
and use energy
Practically Speaking
 Anaerobic refers to activities that are high in intensity, but
short in duration
Practically Speaking
 Aerobic refers to activities that are low-to-moderate in
intensity and longer in duration.
Difference
 The key factor that
differentiates the two is
how quickly you are able to
circulate oxygen to your
muscles (cardiorespiratory
fitness) versus how quickly
you are transferring energy
Difference
 If energy demand exceeds
oxygen delivery, you are
performing anaerobic
exercise
 If oxygen delivery meets or
exceeds energy demand,
you are performing aerobic
exercise
Energy Transfer
 The ATP-CP system relying on the “Phosphogens”.
 Anaerobic
 The glycolytic (lactic acid) system relying on anaerobic
breakdown of CHO.
 The oxidative system relying on the aerobic breakdown of
 CHO, Fat, and Protein.
Energy Pathways
minutes
Source: Insel, P., Turner, R.E., and Ross, D. (2006). Discovering Nutrition. Second
edition. Sudbury, MA: Jones and Bartlett Publishers.
Anaerobic Metabolism
 Anaerobic metabolism refers to the transfer of energy when
there is a limited amount of oxygen available.
 This occurs when we are first starting to move and also when
we are active at high intensity.
 At these times, the need for energy is greater than the speed
at which the blood can deliver oxygen.
Anaerobic Activities
 The ATP-CP and glycolytic systems are major contributors of
energy during the early minutes of high-intensity exercise.
Intramuscular ATP
 ATP
ADP + P and release of E
 ATPase
 7.6 kcal per mole.
 Phosphorylation - process of storing energy by forming ATP
from other chemical sources.
Creatine Phosphate
 In the ATP-CP system, Pi is separated from CP through the
action of creatine kinase.
 The Pi can then combine with ADP to reform ATP.
Creatine Phosphate
 This system is anaerobic.
 Main function is to maintain ATP levels.
 Lasts for only 3 - 15 seconds.
 Energy yield is 1 mole of ATP per 1 mole of CP.
Glycolysis
 The glycolytic system involves the process of glycolysis,
through which glucose is broken down to pyruvic acid via
glycolytic enzymes.
 When conducted without oxygen, the pyruvic acid is
converted to lactic acid.
 One mole of glucose yields 2 moles of ATP, but 1 mole of
glycogen yields 3 moles of ATP.
High-intensity Exercise
 The ATP-CP and glycolytic systems are major contributors of
energy during the early minutes of high-intensity exercise.
Key Processes
 Gluconeogenesis:
 The process by which protein or fat is converted into glucose.
 Glycogenesis:
 The process by which glycogen is synthesized from glucose.
 Glycogenolysis:
 Breakdown of glycogen for ATP production.
Energy Pathways
minutes
Source: Insel, P., Turner, R.E., and Ross, D. (2006). Discovering Nutrition. Second
edition. Sudbury, MA: Jones and Bartlett Publishers.
Aerobic Activities
 The oxidative system
involves breakdown of fuels
with the aid of oxygen
 This system yields much
more energy that the ATPCP (phosphogens) or
glycolytic systems
Aerobic Metabolism
 Aerobic metabolism refers to the process whereby energy is
transferred in the presence of oxygen.
 In aerobic metabolism, energy demand does not outpace
oxygen delivery.
Aerobic Metabolism
 Your heart and circulatory system are able to deliver oxygen
in sufficient quantities to meet the body’s needs for energy
transfer.
 In this circumstance, you initially use carbohydrate as a fuel
source and then shift to fat as the primary source.
Aerobic Metabolism
 If the intensity remains relatively low, this type of activity can
go on indefinitely.
 The only limiting factors will be orthopedic stress and low
levels of carbohydrate (fat burns in a CHO flame).
Aerobic Metabolism
 Oxidation of CHO involves glycolysis, the Kreb’s cycle, and
the electron transport system.
 The end result is water, CO2 and 36 or 38 ATP per molecule
of glucose (38 or 39 per molecule of glycogen).
Aerobic Metabolism
 Fat oxidation begins with oxidation of free fatty acids, then
follows the same path as CHO oxidation:
 the Kreb’s cycle
 and the electron transfer system.
 The energy yield for fat oxidation is much higher than for
CHO oxidation, and it varies with the free fatty acid being
oxidized.
 Example:You can get up to 463 kCals per fat molecule
 (stearic acid)
Electron Transfer System
 Final metabolic pathway in the production of ATP
 Series of chemical reactions in the mitochondria that transfer
electrons from the hydrogen atom carriers NAD and FAD to
oxygen
 Accounts for the majority of the ATP formation
Ketone Bodies and Ketosis
 Ketone Bodies:
 Strong acids
 Give breath fruity smell
 Produced when CHO is not available during fat metabolism
 Ketosis
 When ketone bodies accumulate, ketosis occurs
 Upsets acid-base balance
 Most likely caused by anorexia or diabetes
Aerobic Metabolism
 Protein oxidation is more complex because protein (amino
acids) contains nitrogen, which cannot be oxidized.
 Protein contributes relatively little to energy production, so
its metabolism is often overlooked.
Protein
 Protein can supply up to 5% to 10% of the energy needed to
sustain prolonged exercise.
 Only the most basic units of protein - amino acids can be
used for energy.
Protein
 Alternatively, protein can be converted through a series of
reactions into fatty acids in a process called lipogenesis.
Fuel Summary
 CHO
 Used anaerobically and aerobically
 Low amount stored in body
 Fats
 Used only aerobically
 Large amounts stored in body
 Can only be used if CHO is available
 Protein
 Only used in starvation states
Aerobic Metabolism
 Your muscles’ oxidative capacity (QO2) depends on its
oxidative enzyme levels, its fiber-type composition, and
oxygen availability.
 The greater the QO2 the more fit the muscle.
Energy Measurement
 Direct calorimetry involves using a calorimeter to directly
measure heat produced by the body.
Energy Measurement
 Indirect calorimetry involves measuring O2 consumption and
CO2 release, calculating the RER (or RQ) value (the ratio of
these two gas measurements), comparing it to standard
values to determine the foods being oxidized, then
calculating the energy expended per liter of oxygen
consumed.
RQ
 RQ = VCO2/VO2
Energy Measurement
 For CHO
 6O2 + C6H12O6 = 6CO2 + 6H2O + energy
 RQ
= 6CO2/6O2 = 1.0
Energy Measurement
 The RQ value at rest is usually 0.78 to 0.80.
Respiratory
Quotient
 0.71
 0.75
 0.80
 0.85
 0.90
 0.95
 1.00
Energy
kcal. L-1O2
4.69
4.74
4.80
4.86
4.92
4.99
5.05
%kcal %kcal
CHO Fats
0
100.0
15.6
84.4
33.4
66.6
50.7
49.3
67.5
32.5
84.0
16
100.0
0
Myth
 Only low intensity exercise causes you to burn fat and lose
weight
 Corollary – avoid high intensity exercise if you want to lose
fat
FALSE
Truth
 While fat is the predominant energy source during low-to-
moderate intensity exercise, it is also the predominant
energy source when recovering from all forms of exercise.
 Energy out > energy in
 Use more total energy to lose more total weight
Energy Measurement
 Isotopes can be used to determine metabolic rate.
 They are ingested into the body or injected then traced as
they move through it.
 The rates at which they are cleared can be used to calculate
CO2 production and then caloric expenditure.
EPOC
(Excess Post Exercise Oxygen Consumption)
 When we start exercise, we initially have difficulty getting
enough oxygen to our muscles
 Therefore, when we start exercise, we are performing
anaerobic exercise
EPOC
 Eventually, if the intensity is not too high, we are able to get
the necessary amount of oxygen to the muscles
 This is why the initial moments of exercise feel
uncomfortable and why within a few moments we get our
“second wind”
 Our fitness level determines how quickly this occurs
EPOC
 However, the energy used anaerobically at the start needs to
be eventually replaced
 This is why we breathe hard after exercise
EPOC
 Excess post-exercise oxygen consumption (EPOC) is the
elevation above resting oxygen consumption that occurs after
exercise.
Anaerobic Metabolism
 Traditionally, EPOC was thought to reflect the anaerobic
effort of exercise, but this is too simplistic.
 Several factors contribute to cause this increased post-
exercise need for oxygen.
 See list (next slide).
Role of O2 Consumption During Recovery
 Replenish phosphogens
 ~25% replenishment of glycogen from LA (main source is








post exercise CHO)
Meet physiological demands of recovery
Meet demands of increased temperature and metabolism
Reload blood oxygen
Reload intramuscular oxygen
Serve respiratory muscles
Serve heart
Restock electrolytes and minerals
Restore hormonal balance
Anaerobic Metabolism
 When we use carbohydrate anaerobically, one of the by-
products is an accumulation of lactic acid.
 The hydrogen ions released during the formation of lactic
acid upset the acid-base balance in the body, leading to
muscle fatigue.
OBLA
 OBLA, or the onset of
blood lactic acid, occurs
when oxygen delivery does
not catch up with energy
demand (intensity too
high)
Anaerobic Metabolism
 Lactate threshold is the point at which blood lactate begins to
rapidly accumulate above resting levels during exercise.
 The onset of blood lactate accumulation (OBLA) is a
standard value set at either 2.0 or 4.0 mmol lactate .L-1O2
and is used as a common reference point.
Anaerobic Metabolism
 This explains why we can only be active at high intensities for
short periods of time.
 As the intensity of the activity diminishes, adequate amounts
of oxygen are delivered and the lactic acid is reconverted to
pyruvic acid, which can then be used as a fuel
source.
Anaerobic Metabolism
 Individuals with higher lactate thresholds or OBLA values,
expressed as a percent of their VO2max, are capable of the best
endurance performance.
Myth
 The accumulation of lactic acid is responsible for the muscle
soreness we feel 24 to 48 hours (and longer) after exercise.
FALSE
Truth
 Lactic acid is removed from your body as oxygen is delivered
to your muscles
 During recovery, lactic acid levels drop immediately and do
not contribute to muscle soreness
Truth
 Delayed onset muscle soreness (DOMS) is caused by an
inflammation response triggered by microscopic damage to
muscles caused by stressing them beyond their capabilities
 The inflammation response causes swelling, tenderness, heat
production, and pain.
Factors Influencing Metabolism
 Daily Energy Expenditure
 Endocrine Function
 Nutrition
 Age
 Genetics
 Drugs
 Health
 Sex (male/female)
 Organ Function
 Body Composition
Daily Energy Expenditure.
 Resting metabolic rate (RMR).
 Thermic effect of activity (TEA).
 Thermic effect of feeding (TEF).
 Thermic effect of a meal is the energy that is expended to digest,
metabolize, and store ingested macronutrients.
Resting Metabolic Rate
 This is the rate of energy expenditure when you are in an
awake, resting state.
 Differs from Basal Metabolic Rate
BMR vs. RMR
 The major difference between basal (BMR) and resting
metabolic rate (RMR) is the slightly higher energy expended
during resting metabolic rate (approximately 3%) as a result
of subject arousal.
Resting Metabolic Rate
 In the average adult human, resting metabolic rate is
approximately 1 kcal/min.
 Resting metabolic rate is highly variable between individuals
(+ 25%), but is consistent within individuals (+ 5%).
Resting Metabolic Rate
 Because RMR occurs predominantly in muscle and the major
organs, the main source of individual variability in RMR is
organ and muscle mass.
Resting Metabolic Rate
 RMR is also influenced by sex in that males have a higher
value than females by approximately 50 kcal/d.
Sex
 Absolute energy expenditure is significantly higher in males
compared to females by 741 kcal/d (2440 + 502 kcal/d in
females; 3158 + 742 kcal/d in males), and non-resting
energy expenditure is also higher in men by about 263
kcal/d.
Resting Metabolic Rate
 Collectively, fat-free mass, fat mass, age, sex, and physical
activity explain 80% to 90% of the variance in RMR.
Resting Metabolic Rate
 In addition, a portion of the unique variance in RMR across
individuals has been ascribed to genetic factors, although the
specific source of this genetic variation is not yet identified.
Impact of Exercise on Metabolism (TEA)
 During exercise.
 After exercise.
 Resistance training.
Metabolic Rate
 Basal metabolic rate (BMR) is the minimum amount of
energy required by your body to sustain basic cellular
functions.
 It is measured under rigid testing conditions.
Metabolic Rate
 BMR is highly related to fat-free body mass and body surface area,
though many other factors can affect it.
 Resting Metabolic Rate (RMR)
Metabolic Rate
 BMR is typically in the range of 1,200 to 2,400 kcal . day-1.
 But, when daily activity is added in, the typical daily caloric
expenditure is 1,800 to 3,000 kcal . day-1.
 Energy expenditure for very large athletes in intense daily
training can exceed 10,000 kcals per day.
VO2max
 Metabolism increases with increased exercise intensity, but
oxygen consumption is limited.
 Its peak value is called your VO2max.
VO2max
 Individuals with higher lactate thresholds or OBLA values,
expressed as a percent of their VO2max, are capable of the best
endurance performance.
Training
 Performance improvements often mean the individual can
perform for longer periods at a higher percentage of his or
her VO2max.
VO2max
 Aerobic capacities of 80 to 84 ml.kg-1.min-1 have been
observed among elite male long-distance runners and crosscountry skiers.
VO2max
 The highest VO2max value
recorded for a male is
from an Olympic
champion cross-country
skier who had a VO2max of
94 ml.kg-1.min-1.
VO2max
 The highest recorded for a
female is 82 ml.kg-1.min-1
in a Russian cross-country
skier.
 In contrast, poorly
conditioned adults (couch
potatoes) may have values
below 20 ml.kg-1.min-1.
Training
 To improve anaerobic capabilities
 Perform high intensity activities
 Sprinting
 Jumping
 Lifting
 Plyometrics
 Take minimal rest breaks
Training
 To improve aerobic capabilities
 Perform endurance type activities
 Walking
 Jogging
 Distance cycling
 Distance swimming
 Perform continuous activity for long durations
Training
 To improve both
 Perform combination activities
 Circuit training
 Interval training
 Intersperse high intensity activities with low-to-moderate
intensity activities
 Sprint – jog – sprint
 Lift heavy load – lift light load – lift heavy load
Economy of Effort
 Performance capacity can also be improved by increasing the
economy of effort.
 Low VO2 value for the same rate of work.
Summary
 Success in anaerobic activities depends upon
 High percentage of fast twitch fibers
 High lactate threshold
 High lean weight to body weight ratio
 Good biomechanics
Summary
 Success in aerobic activities depends on the following:
 High VO2max
 High lactate threshold or OBLA
 High economy of effort
 High percentage of ST muscle fibers.
Fatigue
 Fatigue may result from depletion of CP or glycogen.
 Either of these situations impairs ATP production.
Fatigue
 Lactic acid has often been blamed for fatigue, but it is actually
the H+ generated by lactic acid that leads to fatigue.
 The accumulation of H+ decreases muscle pH, which impairs
the cellular processes that produce energy and muscle
contraction.
Fatigue
 Failure of neural transmission may be a cause of some fatigue.
 Many mechanisms can lead to such failure, and all need
further research.
Fatigue
 The CNS may also cause fatigue, perhaps as a protective
mechanism.
 Perceived fatigue usually precedes physiological fatigue, and
athletes who feel exhausted can often be psychologically
encouraged to continue.
Fatigue
 Failure of the fiber’s contractile mechanism.