Exercise Physiology Exam 1

homeostasis

Maintenance of a constant internal environment
Rest

steady state

Balance between the demands placed on a body and the physiological response to those demands
Variables are constant and unchanging

biological control system

To regulate some physiological variable at or near constant value
Cells and organ systems
Series of interconnected components that serve to maintain a physical or chemical parameter at or near constant

receptor

Sensor (Receptor)
Capable of detecting changes

effector

Corrects changes to internal environment

integrating center

Assesses input and initiates response

negative feedback

Most biological control systems
Response reverses the initial disturbance in homeostasis

What is meant by "Gain of a control system"?

Degree and precision to which the control system maintains homeostasis
System with large gain is more capable of maintaining homeostasis
Regulation of body temperature, breathing, delivery of blood

How does homeostasis differ from steady state?

Exercise disrupts homeostasis by changes in pH, O2, CO2, and temperature
Control systems are capable of maintaining steady state during submaximal exercise in a cool environment

ADP

...

ATP

ATP - adenosine triphosphate
stores energy in the high-energy phosphate bonds
takes energy from food and transfers to energy requiring processes
Ex: Muscle contraction
only ~ 85g of ATP stored in body so must continually re-synthesize

Aerobic

ATP production-->
Mitochondria
1: Krebs Cycle
Complete oxidation of CHO, fats, proteins
2: Electron Transport Chain
ATP formed from ADP + Pi
Required for aerobic resynthesis of ATP:
donor electrons from NADH and FADH
adequate oxygen
adequate enzymes, co-e

Anaerobic

creating ATP without O2

NAD

Nicotinamide adenine dinucleotide

FAD

Flavin adenine dinucleotide

Oxidation

removing electron

Reduction

adding electron

Endergonic rxn

Require energy to be added

Exergonic rxn

release energy

ATP-PC

...

glycolysis

...

enzyme

...

mitochondria

...

coupled rxn

Liberation of energy in an exergonic reaction drives an endergonic reaction

glucose

blood sugar

glycogen

storage form of glucose in liver

oxidative phosphorylation

aerobic method of making ATP

Krebs cycle

Krebs cycle (citric acid cycle)
Pyruvic acid (3 C) is converted to acetyl-CoA (2 C)
CO2 is given off
Acetyl-CoA combines with oxaloacetate (4 C) to form citrate (6 C)
Citrate is metabolized to oxaloacetate
Two CO2 molecules given off
Produces three molecu

electron transport chain

...

triglycerides

Fatty acids
Primary type of fat used by the muscle
Triglycerides
Storage form of fat in muscle and adipose tissue
Breaks down into glycerol and fatty acids
Phospholipids
Not used as an energy source
Steroids
Derived from cholesterol
Needed to synthesize s

chemiosmotic hypothesis

Electron transport chain results in pumping of H+ ions (protons) across inner mitochondrial membrane
Results in greater H+ gradient across membrane
Energy released to form ATP as H+ ions diffuse back across the membrane
3 different pumps move H+ to inter-

bioenergentics

converting foodstuffs into usable CHO, fats, proteins

beta oxidation

...

glycogenolysis

Breakdown of glycogen to glucose

metabolism

Sum of all chemical reactions that occur in the body
Anabolic reactions
Synthesis of molecules
Catabolic reactions
Breakdown of molecules

What is an oxidation-reduction rxn?

Oxidation and reduction are always coupled reactions
Often involves the transfer of hydrogen atoms rather than free electrons
Hydrogen atom contains one electron
A molecule that loses a hydrogen also loses an electron and therefore is oxidized
Importance

How do temp. and pH effect enzyme activity?
Why is this important during exercise?

Catalysts that regulate the speed of reactions
Lower the energy of activation
Factors that regulate enzyme activity
Temperature
pH
Interact with specific substrates
Lock and key model
Many enzymes have higher activity at slightly above normal temperature

What are the different classes of enzymes that we will encounter in HPS 4300?

Oxidoreductases
Catalyze O-R reactions
Lactate dehydrogenase
Transferases
Catalyze transfer of elements between molecules
Hexokinase
Hydrolases
Bonds are broken by adding water
Lipase
Lyases
Affects formation of double bonds
Carbonic anhydrase
Isomerases

What are some characteristics of the substrate CHO?

Glucose
Blood sugar
Glycogen
Storage form of glucose in liver and muscle
Synthesized by enzyme glycogen synthase
Glycogenolysis
Breakdown of glycogen to glucose

What are some of the characteristics of the substrate fat?

triglycerides are the primary storage form of fats (glycerol + 3 fatty acids)
lipolysis necessary to remove energy
hormone sensitive lipase
TG + 3H2O <-----> glycerol + 3FA
FA broken down into 2-C fragments during beta () oxidation
2-C fragments join w/ C

Describe adenosine triphosphate

...

What are the characteristics of the ATP-PC system?

PHOSPHOCREATINE - PC
a high energy phosphate stored in the body
PC + ADP ----------> ATP + Creatine

Where does glycolysis occur?

First step: glucose to glucose-6-phosphate
catalyzed by hexokinase
requires ATP
traps the molecule w/in the cytoplasm
G-6-P can also be formed from glycogen (no ATP req. so net gain from glycogen 3 ATP):

How many ATP are required as an initial investment in glycolysis?

...

How many ATP are produced from glycolysis (gross and net)?

Breakdown of glucose or glycogen to yield energy
Anaerobic
Net yield from 1 glucose molecule
2 pyruvic acid
2 ATP
2 NADH

What is different about glycolysis when glycogen is the substrate we start with?

G-6-P can also be formed from glycogen (no ATP req. so net gain from glycogen 3 ATP):

What is the role of hexokinase?

Transfers a phosphate group from ATP to glucose

What is the role of Phosphfructokinase?

Transfers a phosphate group from ATP to form fructose 1, 6-biphosphate

At which steps of glycolysis are NAD and ATP formed?

Step 6, beginning of energy generation phase and step 7, step 10 pyruvate kinase mediates transfer of phosphates from phophoenolpyruvate to ADP

How and when is lactic acid formed?

Lactate dehydrogenase transfers H+ to pyruvic acid from NADH, formation of lactate occurs, anaerobic
formation of lactic acid occurs when NADH gives up H+ to pyruvic acid:
lactate dehydrogenase
pyruvic acid + NADH ----> lactic acid + NAD
NOTE: process can

We get 2 NADH and 4 ATP from the energy generation phase of glycolysis, explain why we don't get just 1 NADH and 2 ATP?

steps 7 and 10 release 2 ATP each, and 2 NADH are made in first step of energy gen phase

Summarize the steps in the energy investment phase of glycolysis

...

Summarize the steps in the energy generation phase of glycolysis

...

What are 3 things required for the aerobic production of ATP?

...

What is the 3 stage process of aerobic ATP formation?

Krebs cycle (citric acid cycle)
Pyruvic acid (3 C) is converted to acetyl-CoA (2 C)
CO2 is given off
Acetyl-CoA combines with oxaloacetate (4 C) to form citrate (6 C)
Citrate is metabolized to oxaloacetate
Two CO2 molecules given off
Produces three molecu

What are the by products of aerobic metabolism?

Two CO2 molecules given off
Produces three molecules of NADH and one FADH2
Also forms one molecule of GTP
Produces one ATP

How is pyruvate converted to acetyl-coA?

pyruvate + NAD+ + CoA ------->Acetyl CoA + CO2 + NADH
pyruvate dehydrogenase

What are NADH and FADH worth in terms of ATP production?

Each NADH yields approx 2.5 ATP
Each FADH yields approx 1.5 ATP

How do we end up with 32 ATP from 1 glucose molecule?

Glycolysis--> 2ATP=2 ATP (anaerobic) 2 NADH+5 ATP from OP=
7 ATP (anaerobic)
Pyruvic Acid-Acetyl CoA--> 2 NADH + 5ATP from OP=12 ATP
Krebs-->2GTP=14 ATP
6 NADH + 15 from OP=29 ATP
2 FADH + 3 ATP from OP=32ATP

Why is B-oxidation important?

Breakdown of triglycerides releases fatty acids
Fatty acids must be converted to acetyl-CoA to be used as a fuel
Activated fatty acid (fatty acyl-CoA) into mitochondrion
Fatty acid "chopped" into 2 carbon fragments forming acetyl-CoA
Acetyl-CoA enters Kre

What stimulates/inhibits ATP-PC?

Stimulates: ADP
Inhibits:ATP

What stimulates/inhibits glycolysis?

Stimulates: AMP, ADP, P, pH^
Inhibits: ATP, CP, citrate, pHv

What stimulates/inhibits Krebs cycle?

S:ADP, Ca, NAD
I: ATP, NADH

What stimulates/inhibits ETC?

S: ADP, P
I: ATP

What are the rate limiting enzymes for glycolysis and Krebs cycle?

An enzyme that regulates the rate of a metabolic pathway
Glycolysis-->phosphofructokinase
Krebs-->Isocitrate dehydrogenase
Levels of ATP and ADP+Pi
High levels of ATP inhibit ATP production
Low levels of ATP and high levels of ADP+Pi stimulate ATP product

Cori cycle

The cycle whereby glucose is broken down into lactate,
Transported to the liver,
Turned back into glucose,
Then transported back to the muscles

EPOC

Excess post-exercise oxygen consumption (EPOC)
Terminology reflects that only ~20% elevated O2 consumption used to "repay" O2 deficit
EPOC is greater following higher intensity exercise-->
Higher body temperature
Greater depletion of PC
Greater blood conc

free fatty acid

...

gluconeogenisis

convert lactate to glucose (gluconeogenesis),

glycerol

...

lactate/lactate threshold

Lactate is the form in which lactic acid is measured
both terms can be used
Produced in many of the cells of the body but particularly in muscle cells during exercise
From these cells lactate diffuses out into the blood where it can be measured
Accumulati

lipase

...

lipolysis

Lipolysis: breakdown of TG to ffa and glycerol by lipases
In the adipocyte: hormone-sensitive lipase
Lipases are inactive until stimulated by epi, nor-epi, and glucagon
Inhibited by insulin and high levels of BL

maximal oxygen uptake

maximal oxygen consumption or maximal oxygen uptake (aka: aerobic capacity)
reflects physical fitness of a person
Expressed either as an absolute rate in litres of oxygen per minute (l/min) or as a relative rate in milliliters of oxygen per kilogram of bo

oxygen debt

The oxygen debt (also called excess post-exercise oxygen consumption [EPOC]) is the O2 consumption above rest following exercise

oxygen deficit

Lag in oxygen uptake at the beginning of exercise
Suggests ATP-PC and glycolysis major contributors to total ATP production

respiratory exchange ratio

...

triglyceride

...

Difference between absolute and relative VO2?

VO2max is the maximum capacity to transport and utilize oxygen during incremental exercise
VO2max is the maximum capacity to transport and utilize oxygen during incremental exercise
maximal oxygen consumption or maximal oxygen uptake (aka: aerobic capacit

Under which conditions the different energy systems are most utilized?

Nearly 100% of energy required at rest is produced from oxidative phosphorylation
Resting blood lactate levels are low and steady (~1-2 mmol/L)
Measurement of O2 consumption at rest gives us a baseline of energy requirements.
Ex: 70kg adult has resting VO

What effect does training have on oxygen deficit?

ATP production increases immediately
Oxygen uptake increases rapidly
Reaches steady state within 1-4 minutes
Oxygen deficit
Lag in oxygen uptake at the beginning of exercise
Suggests ATP-PC and glycolysis major contributors to total ATP production
Trained

What constitutes the fast portion of EPOC?

Resynthesis of stored PC
Replacing muscle and blood O2 stores

What constitutes the slow portion of EPOC?

Elevated heart rate and breathing, due to energy need
Elevated body temperature, due to metabolic rate
Elevated epinephrine & norepinephrine, due to metabolic rate
Conversion of lactate to glucose (gluconeogenesis)

What effects the removal of lactate?

The process of lactate removal takes approx. one hour, but can be accelerated by a cool down at 30-40% VO2max which ensures a continuous supply of oxygen to the muscles.
Classic theory
Majority of lactate converted to glucose in liver
Recent evidence
70%

What contributes the upward drift in O2 uptake?

Room air is approx = 20.93% O2, 0.03% CO2, and the rest is N
Humans use O2 and therefore expired air contains 16-18.5% O2 (less O2 than room air)
The difference represents the O2 extracted by the lungs and transported throughout the body for aerobic metab

What is meant by the "metabolic fork in the road"?

At this fork, glucose has been converted pyruvate (glycolysis).
Pyruvate:
-Acetyl Co A
-Lactate
-Oxaloacetate
-Alanine
Pyruvate has no say in this, the conditions in the muscle determine its fate

What uses does the body have for lactate?

Lactate diffuses out of cell and delivered to:
Liver
Heart
Other skeletal muscles
USES-->
-Oxidize it (use it as a fuel source)
Convert back to pyruvate by reversing the reaction that occurred in the muscle
-Gluconeogenesis
mostly confined to the liver
Ca

What causes the lactate threshold to occur?

The normal pH of the muscle cell is 7.1 but if the build up of H+ continues and pH is reduced to around 6.5 then muscle contraction may be impaired and the low pH will stimulate the free nerve endings in the muscle resulting in the perception of pain (the

What effect does training have on lactate threshold?

Training Status of Active Muscles
If you train for endurance:
Higher mitochondrial volume
Improved fatty acid oxidation capacity
Fat metabolism proceeds via a different pathway than glucose
High capillary density
Effect of Training
Untrained individuals u

Explain the "mitochondrial hydrogen shuttle" and what factors might effect it?

Failure of the mitochondrial hydrogen shuttle to keep pace with glycolysis
Excess NADH in sarcoplasm favors conversion of pyruvate to lactate
Type of LDH
Enzyme that converts pyruvate to lactate
LDH in fast-twitch fibers favors formation of lactate
Hydrog

How do we estimate fuel utilization during exercise?

Respiratory exchange ratio (RER or R)
Non-invasive method of estimating % contribution of CHO and fat
R = VCO2 / VO2
Values between 0.70 and 1.0
Values >1.0 indicate hyperventilation
"R" or "RER" indicates fuel utilization
0.70 = 100% fat
0.85 = 50% fat,

How does intensity, duration, and training influence fuel utilization?

Intensity-->
Low-intensity exercise (<30% VO2max)
Fats are primary fuel
High-intensity exercise (>70% VO2max)
CHO are primary fuel
"Crossover" concept
Describes the shift from fat to CHO metabolism as exercise intensity increases
Due to:
Recruitment of fa

Why is it so "hard" to utilize fat as the energy source (7 steps)?

1) Mobilization (in adipocyte)
Lipolysis by hormone sensitive lipase
2) Circulation
Glycerol and FFA transported in blood
3) Uptake
Proteins move FFA into muscle cells
4) Activation
Co-enzyme A involved, fatty acyl-CoA is product
5) Translocation
Fatty ac

Fats burn in a CHO flame" Why?

hint: Krebs cycle is important here, particularly the intermediate oxaloacetate, which binds with acetyl coA to form citrate at the beginning of Krebs cycle
Short-term exercise
Unlikely to deplete glycogen/blood glucose
Prolonged exercise
Muscle and liver

Sources of fuel during exercise

-Muscle glycogen
Primary source of carbohydrate during high-intensity exercise
Supplies much of the carbohydrate in the first hour of exercise
-Blood glucose
From liver glycogenolysis
Primary source of carbohydrate during low-intensity exercise
Important

fatigue

In the cell:
pH is lowered
If enough lactate is produced, the pH goes down far enough to affect the tertiary structure of every enzyme in the cell, decreasing their function.
This causes a loss of performance that we call fatigue

Factors contributing to EPOC

Resynthesis of PC in muscle
Lactate conversion to glucose
Restoration of muscle and blood oxygen stores
Elevated body temp
post-exercise elevation of HR and breathing
Elevated hormones

homeostasis

Maintenance of a constant internal environment
Rest

steady state

Balance between the demands placed on a body and the physiological response to those demands
Variables are constant and unchanging

biological control system

To regulate some physiological variable at or near constant value
Cells and organ systems
Series of interconnected components that serve to maintain a physical or chemical parameter at or near constant

receptor

Sensor (Receptor)
Capable of detecting changes

effector

Corrects changes to internal environment

integrating center

Assesses input and initiates response

negative feedback

Most biological control systems
Response reverses the initial disturbance in homeostasis

What is meant by "Gain of a control system"?

Degree and precision to which the control system maintains homeostasis
System with large gain is more capable of maintaining homeostasis
Regulation of body temperature, breathing, delivery of blood

How does homeostasis differ from steady state?

Exercise disrupts homeostasis by changes in pH, O2, CO2, and temperature
Control systems are capable of maintaining steady state during submaximal exercise in a cool environment

ADP

...

ATP

ATP - adenosine triphosphate
stores energy in the high-energy phosphate bonds
takes energy from food and transfers to energy requiring processes
Ex: Muscle contraction
only ~ 85g of ATP stored in body so must continually re-synthesize

Aerobic

ATP production-->
Mitochondria
1: Krebs Cycle
Complete oxidation of CHO, fats, proteins
2: Electron Transport Chain
ATP formed from ADP + Pi
Required for aerobic resynthesis of ATP:
donor electrons from NADH and FADH
adequate oxygen
adequate enzymes, co-e

Anaerobic

creating ATP without O2

NAD

Nicotinamide adenine dinucleotide

FAD

Flavin adenine dinucleotide

Oxidation

removing electron

Reduction

adding electron

Endergonic rxn

Require energy to be added

Exergonic rxn

release energy

ATP-PC

...

glycolysis

...

enzyme

...

mitochondria

...

coupled rxn

Liberation of energy in an exergonic reaction drives an endergonic reaction

glucose

blood sugar

glycogen

storage form of glucose in liver

oxidative phosphorylation

aerobic method of making ATP

Krebs cycle

Krebs cycle (citric acid cycle)
Pyruvic acid (3 C) is converted to acetyl-CoA (2 C)
CO2 is given off
Acetyl-CoA combines with oxaloacetate (4 C) to form citrate (6 C)
Citrate is metabolized to oxaloacetate
Two CO2 molecules given off
Produces three molecu

electron transport chain

...

triglycerides

Fatty acids
Primary type of fat used by the muscle
Triglycerides
Storage form of fat in muscle and adipose tissue
Breaks down into glycerol and fatty acids
Phospholipids
Not used as an energy source
Steroids
Derived from cholesterol
Needed to synthesize s

chemiosmotic hypothesis

Electron transport chain results in pumping of H+ ions (protons) across inner mitochondrial membrane
Results in greater H+ gradient across membrane
Energy released to form ATP as H+ ions diffuse back across the membrane
3 different pumps move H+ to inter-

bioenergentics

converting foodstuffs into usable CHO, fats, proteins

beta oxidation

...

glycogenolysis

Breakdown of glycogen to glucose

metabolism

Sum of all chemical reactions that occur in the body
Anabolic reactions
Synthesis of molecules
Catabolic reactions
Breakdown of molecules

What is an oxidation-reduction rxn?

Oxidation and reduction are always coupled reactions
Often involves the transfer of hydrogen atoms rather than free electrons
Hydrogen atom contains one electron
A molecule that loses a hydrogen also loses an electron and therefore is oxidized
Importance

How do temp. and pH effect enzyme activity?
Why is this important during exercise?

Catalysts that regulate the speed of reactions
Lower the energy of activation
Factors that regulate enzyme activity
Temperature
pH
Interact with specific substrates
Lock and key model
Many enzymes have higher activity at slightly above normal temperature

What are the different classes of enzymes that we will encounter in HPS 4300?

Oxidoreductases
Catalyze O-R reactions
Lactate dehydrogenase
Transferases
Catalyze transfer of elements between molecules
Hexokinase
Hydrolases
Bonds are broken by adding water
Lipase
Lyases
Affects formation of double bonds
Carbonic anhydrase
Isomerases

What are some characteristics of the substrate CHO?

Glucose
Blood sugar
Glycogen
Storage form of glucose in liver and muscle
Synthesized by enzyme glycogen synthase
Glycogenolysis
Breakdown of glycogen to glucose

What are some of the characteristics of the substrate fat?

triglycerides are the primary storage form of fats (glycerol + 3 fatty acids)
lipolysis necessary to remove energy
hormone sensitive lipase
TG + 3H2O <-----> glycerol + 3FA
FA broken down into 2-C fragments during beta () oxidation
2-C fragments join w/ C

Describe adenosine triphosphate

...

What are the characteristics of the ATP-PC system?

PHOSPHOCREATINE - PC
a high energy phosphate stored in the body
PC + ADP ----------> ATP + Creatine

Where does glycolysis occur?

First step: glucose to glucose-6-phosphate
catalyzed by hexokinase
requires ATP
traps the molecule w/in the cytoplasm
G-6-P can also be formed from glycogen (no ATP req. so net gain from glycogen 3 ATP):

How many ATP are required as an initial investment in glycolysis?

...

How many ATP are produced from glycolysis (gross and net)?

Breakdown of glucose or glycogen to yield energy
Anaerobic
Net yield from 1 glucose molecule
2 pyruvic acid
2 ATP
2 NADH

What is different about glycolysis when glycogen is the substrate we start with?

G-6-P can also be formed from glycogen (no ATP req. so net gain from glycogen 3 ATP):

What is the role of hexokinase?

Transfers a phosphate group from ATP to glucose

What is the role of Phosphfructokinase?

Transfers a phosphate group from ATP to form fructose 1, 6-biphosphate

At which steps of glycolysis are NAD and ATP formed?

Step 6, beginning of energy generation phase and step 7, step 10 pyruvate kinase mediates transfer of phosphates from phophoenolpyruvate to ADP

How and when is lactic acid formed?

Lactate dehydrogenase transfers H+ to pyruvic acid from NADH, formation of lactate occurs, anaerobic
formation of lactic acid occurs when NADH gives up H+ to pyruvic acid:
lactate dehydrogenase
pyruvic acid + NADH ----> lactic acid + NAD
NOTE: process can

We get 2 NADH and 4 ATP from the energy generation phase of glycolysis, explain why we don't get just 1 NADH and 2 ATP?

steps 7 and 10 release 2 ATP each, and 2 NADH are made in first step of energy gen phase

Summarize the steps in the energy investment phase of glycolysis

...

Summarize the steps in the energy generation phase of glycolysis

...

What are 3 things required for the aerobic production of ATP?

...

What is the 3 stage process of aerobic ATP formation?

Krebs cycle (citric acid cycle)
Pyruvic acid (3 C) is converted to acetyl-CoA (2 C)
CO2 is given off
Acetyl-CoA combines with oxaloacetate (4 C) to form citrate (6 C)
Citrate is metabolized to oxaloacetate
Two CO2 molecules given off
Produces three molecu

What are the by products of aerobic metabolism?

Two CO2 molecules given off
Produces three molecules of NADH and one FADH2
Also forms one molecule of GTP
Produces one ATP

How is pyruvate converted to acetyl-coA?

pyruvate + NAD+ + CoA ------->Acetyl CoA + CO2 + NADH
pyruvate dehydrogenase

What are NADH and FADH worth in terms of ATP production?

Each NADH yields approx 2.5 ATP
Each FADH yields approx 1.5 ATP

How do we end up with 32 ATP from 1 glucose molecule?

Glycolysis--> 2ATP=2 ATP (anaerobic) 2 NADH+5 ATP from OP=
7 ATP (anaerobic)
Pyruvic Acid-Acetyl CoA--> 2 NADH + 5ATP from OP=12 ATP
Krebs-->2GTP=14 ATP
6 NADH + 15 from OP=29 ATP
2 FADH + 3 ATP from OP=32ATP

Why is B-oxidation important?

Breakdown of triglycerides releases fatty acids
Fatty acids must be converted to acetyl-CoA to be used as a fuel
Activated fatty acid (fatty acyl-CoA) into mitochondrion
Fatty acid "chopped" into 2 carbon fragments forming acetyl-CoA
Acetyl-CoA enters Kre

What stimulates/inhibits ATP-PC?

Stimulates: ADP
Inhibits:ATP

What stimulates/inhibits glycolysis?

Stimulates: AMP, ADP, P, pH^
Inhibits: ATP, CP, citrate, pHv

What stimulates/inhibits Krebs cycle?

S:ADP, Ca, NAD
I: ATP, NADH

What stimulates/inhibits ETC?

S: ADP, P
I: ATP

What are the rate limiting enzymes for glycolysis and Krebs cycle?

An enzyme that regulates the rate of a metabolic pathway
Glycolysis-->phosphofructokinase
Krebs-->Isocitrate dehydrogenase
Levels of ATP and ADP+Pi
High levels of ATP inhibit ATP production
Low levels of ATP and high levels of ADP+Pi stimulate ATP product

Cori cycle

The cycle whereby glucose is broken down into lactate,
Transported to the liver,
Turned back into glucose,
Then transported back to the muscles

EPOC

Excess post-exercise oxygen consumption (EPOC)
Terminology reflects that only ~20% elevated O2 consumption used to "repay" O2 deficit
EPOC is greater following higher intensity exercise-->
Higher body temperature
Greater depletion of PC
Greater blood conc

free fatty acid

...

gluconeogenisis

convert lactate to glucose (gluconeogenesis),

glycerol

...

lactate/lactate threshold

Lactate is the form in which lactic acid is measured
both terms can be used
Produced in many of the cells of the body but particularly in muscle cells during exercise
From these cells lactate diffuses out into the blood where it can be measured
Accumulati

lipase

...

lipolysis

Lipolysis: breakdown of TG to ffa and glycerol by lipases
In the adipocyte: hormone-sensitive lipase
Lipases are inactive until stimulated by epi, nor-epi, and glucagon
Inhibited by insulin and high levels of BL

maximal oxygen uptake

maximal oxygen consumption or maximal oxygen uptake (aka: aerobic capacity)
reflects physical fitness of a person
Expressed either as an absolute rate in litres of oxygen per minute (l/min) or as a relative rate in milliliters of oxygen per kilogram of bo

oxygen debt

The oxygen debt (also called excess post-exercise oxygen consumption [EPOC]) is the O2 consumption above rest following exercise

oxygen deficit

Lag in oxygen uptake at the beginning of exercise
Suggests ATP-PC and glycolysis major contributors to total ATP production

respiratory exchange ratio

...

triglyceride

...

Difference between absolute and relative VO2?

VO2max is the maximum capacity to transport and utilize oxygen during incremental exercise
VO2max is the maximum capacity to transport and utilize oxygen during incremental exercise
maximal oxygen consumption or maximal oxygen uptake (aka: aerobic capacit

Under which conditions the different energy systems are most utilized?

Nearly 100% of energy required at rest is produced from oxidative phosphorylation
Resting blood lactate levels are low and steady (~1-2 mmol/L)
Measurement of O2 consumption at rest gives us a baseline of energy requirements.
Ex: 70kg adult has resting VO

What effect does training have on oxygen deficit?

ATP production increases immediately
Oxygen uptake increases rapidly
Reaches steady state within 1-4 minutes
Oxygen deficit
Lag in oxygen uptake at the beginning of exercise
Suggests ATP-PC and glycolysis major contributors to total ATP production
Trained

What constitutes the fast portion of EPOC?

Resynthesis of stored PC
Replacing muscle and blood O2 stores

What constitutes the slow portion of EPOC?

Elevated heart rate and breathing, due to energy need
Elevated body temperature, due to metabolic rate
Elevated epinephrine & norepinephrine, due to metabolic rate
Conversion of lactate to glucose (gluconeogenesis)

What effects the removal of lactate?

The process of lactate removal takes approx. one hour, but can be accelerated by a cool down at 30-40% VO2max which ensures a continuous supply of oxygen to the muscles.
Classic theory
Majority of lactate converted to glucose in liver
Recent evidence
70%

What contributes the upward drift in O2 uptake?

Room air is approx = 20.93% O2, 0.03% CO2, and the rest is N
Humans use O2 and therefore expired air contains 16-18.5% O2 (less O2 than room air)
The difference represents the O2 extracted by the lungs and transported throughout the body for aerobic metab

What is meant by the "metabolic fork in the road"?

At this fork, glucose has been converted pyruvate (glycolysis).
Pyruvate:
-Acetyl Co A
-Lactate
-Oxaloacetate
-Alanine
Pyruvate has no say in this, the conditions in the muscle determine its fate

What uses does the body have for lactate?

Lactate diffuses out of cell and delivered to:
Liver
Heart
Other skeletal muscles
USES-->
-Oxidize it (use it as a fuel source)
Convert back to pyruvate by reversing the reaction that occurred in the muscle
-Gluconeogenesis
mostly confined to the liver
Ca

What causes the lactate threshold to occur?

The normal pH of the muscle cell is 7.1 but if the build up of H+ continues and pH is reduced to around 6.5 then muscle contraction may be impaired and the low pH will stimulate the free nerve endings in the muscle resulting in the perception of pain (the

What effect does training have on lactate threshold?

Training Status of Active Muscles
If you train for endurance:
Higher mitochondrial volume
Improved fatty acid oxidation capacity
Fat metabolism proceeds via a different pathway than glucose
High capillary density
Effect of Training
Untrained individuals u

Explain the "mitochondrial hydrogen shuttle" and what factors might effect it?

Failure of the mitochondrial hydrogen shuttle to keep pace with glycolysis
Excess NADH in sarcoplasm favors conversion of pyruvate to lactate
Type of LDH
Enzyme that converts pyruvate to lactate
LDH in fast-twitch fibers favors formation of lactate
Hydrog

How do we estimate fuel utilization during exercise?

Respiratory exchange ratio (RER or R)
Non-invasive method of estimating % contribution of CHO and fat
R = VCO2 / VO2
Values between 0.70 and 1.0
Values >1.0 indicate hyperventilation
"R" or "RER" indicates fuel utilization
0.70 = 100% fat
0.85 = 50% fat,

How does intensity, duration, and training influence fuel utilization?

Intensity-->
Low-intensity exercise (<30% VO2max)
Fats are primary fuel
High-intensity exercise (>70% VO2max)
CHO are primary fuel
"Crossover" concept
Describes the shift from fat to CHO metabolism as exercise intensity increases
Due to:
Recruitment of fa

Why is it so "hard" to utilize fat as the energy source (7 steps)?

1) Mobilization (in adipocyte)
Lipolysis by hormone sensitive lipase
2) Circulation
Glycerol and FFA transported in blood
3) Uptake
Proteins move FFA into muscle cells
4) Activation
Co-enzyme A involved, fatty acyl-CoA is product
5) Translocation
Fatty ac

Fats burn in a CHO flame" Why?

hint: Krebs cycle is important here, particularly the intermediate oxaloacetate, which binds with acetyl coA to form citrate at the beginning of Krebs cycle
Short-term exercise
Unlikely to deplete glycogen/blood glucose
Prolonged exercise
Muscle and liver

Sources of fuel during exercise

-Muscle glycogen
Primary source of carbohydrate during high-intensity exercise
Supplies much of the carbohydrate in the first hour of exercise
-Blood glucose
From liver glycogenolysis
Primary source of carbohydrate during low-intensity exercise
Important

fatigue

In the cell:
pH is lowered
If enough lactate is produced, the pH goes down far enough to affect the tertiary structure of every enzyme in the cell, decreasing their function.
This causes a loss of performance that we call fatigue

Factors contributing to EPOC

Resynthesis of PC in muscle
Lactate conversion to glucose
Restoration of muscle and blood oxygen stores
Elevated body temp
post-exercise elevation of HR and breathing
Elevated hormones