At rest:
the VO2 is approximately 3.5 ml/kg/min.
Which of the following groups of activities use energy derived predominantly from the ATP-PC system?
gymnastics vault, softball pitch, high jump
The upward drift of VO2 during steady state exercise is primarily due to
increasing body temperature.
The physiological factors that influence VO2max are
A) the delivery of oxygen to the muscle.
B) the uptake and use of oxygen by the muscle.
C) genetics and exercise training.
A factor that contributes to excess post exercise oxygen consumption is
resynthesis of creatine phosphate in muscle.
The rise in blood lactic acid concentration above the lactate threshold can occur due to
A) an increase in lactic acid production.
B) a decrease in lactic acid removal.
During low intensity exercise (i.e., <30% VO2max), the primary fuel source for muscle is
fats
In prolonged (3-4 hours), moderate-intensity exercise, there is an increased reliance on
blood sources of carbohydrate and fat
The shift from fat to carbohydrate metabolism is regulated by
the type of fiber recruited.
The primary determinant of plasma FFA oxidation during exercise is
the blood level of the fuel.
The RQ for fat is
equal to VCO2/VO2.
During the first hour of submaximal exercise, most of the carbohydrate metabolized comes from
muscle glycogen.
The mobilization of free fatty acids into the blood is inhibited by
lactic acid.
Fatigue results after depletion of carbohydrate stores due to the reduction
A) in the muscle concentration of pyruvic acid.
B) of Krebs cycle intermediates.
C) of Krebs cycle activity.
The portion of the oxygen debt that is responsible for the conversion of lactic acid to glycogen is around
20%
The Cori cycle describes:
the steps by which lactic acid is converted to glucose in the liver
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
Lactate Threshold
- Low muscle oxygen
- Accelerated glycolysis
- Recruitment of fast-twitch fibers
- Reduced rate of lactate removal
% of Energy Expenditure of Muscle Glycogen
Hour 1: 45%
Hour 3: 15%
% Energy Expenditure of Blood Glucose
Hour 1: 50%
Hour 3: 45%
% Energy Expenditure of Plasma FFA
Hour 1: 75%
Hour 3: 90%
% Energy Expenditure of Muscle Triglycerides
Hour 1: 100 %
Hour 3: 100%
Rest-to-Exercise Transitions 1:
ATP production increases immediately
Rest-to-Exercise Transitions 2:
Oxygen uptake increases rapidly
Reaches steady state within 1-4
minutes
After steady state is reached,
ATP requirement is met through
aerobic ATP production
Rest-to-Exercise Transitions 3:
Oxygen deficit
Means a lag in oxygen uptake at
the beginning of exercise
Suggests anaerobic pathways
contribute to total ATP
production
Rest-to-Exercise Transitions 4:
Initial ATP production through anaerobic pathways
ATP-PC system
Glycolysis
At steady state VO2,
ATP supply aerobically matches ATP demand
Excess post-exercise oxygen consumption (EPOC)
Terminology reflects that only ~20% elevated O2 consumption used to "repay" O2 deficit
Rapid" portion of O2 debt or EPOC (2 to 3 min post-exercise)
Resynthesis of stored PC
Replenishing muscle and blood O2 stores
Slow" portion of O2 debt or EPOC (>30 min post exercise)
Elevated heart rate and breathing = ^ energy need
Elevated body temperature = ^ metabolic rate
Elevated epinephrine and norepinephrine = ^ metabolic rate
Conversion of lactic acid to glucose (gluconeogenesis)
Why is EPOC greater following higher intensity exercise?
Higher body temperature
Greater depletion of PC
Greater blood concentrations of lactic acid
Higher levels of blood epinephrine and norepinephrine
Removal of Lactic Acid Following Exercise
70% of lactic acid is oxidized
Used as a substrate by heart and skeletal muscle
20% converted to glucose
10% converted to amino acids
(Lactic acid is removed more rapidly with light exercise in recovery)
First 1-5 seconds of exercise
ATP through ATP-PC system
Intense exercise longer than 5 seconds
Shift to ATP production via glycolysis
Events lasting longer than 45 seconds
ATP production through ATP-PC, glycolysis, and aerobic systems
During high-intensity, short-term exercise
the muscle's ATP production is dominated by the ATP-PC system.
high-intensity events lasting longer than forty-five seconds use a combination of
the ATP-PC system, glycolysis, and the aerobic system to produce the needed ATP for muscular contraction, with a 50%/50% (anaerobic/aerobic) contribution needed for exercise lasting between 2 and 3 minutes.
2 Physiological factors influencing VO2 max:
1. Maximum ability of the cardiorespiratory system to deliver oxygen to contracting muscle
2. Ability of muscles to take up the oxygen and produce ATP aerobically
Lactate Threshold
The point at which blood lactic acid suddenly rises during incremental exercise
Lactate threshold occurs in untrained at
50~60& VO2 max
Lactate threshold occurs in trained at
65-80% VO2 max
Onset of Blood Lactate Accumulation (OBLA)
The point (exercise intensity) at which blood lactate levels reach 4 mmol/L
Explanations for the Lactate Threshold
1. Low muscle oxygen
2. Accelerated glycolysis
3. Recruitment of fast-twitch muscle fibers
4. Reduced rate of lactate removal from the blood
Accelerated Glycolysis
NADH produced faster than it is shuttled into mitochondria
Excess NADH in cytoplasm converts pyruvic acid to lactic acid
Recruitment of fast-twitch muscle fibers
LDH isozyme in fast fibers promotes lactic acid formation
LDH in fast-twitch fibers
favors formation of lactic acid because it has a greater affinity for attaching to hydrogen to pyruvate >> leading to increase in lactate production
LDH in slow-twitch fibers
promotes the conversion of lactate to pyruvate >> leading to decrease in lactate
Practical Uses of the Lactate Threshold
1. Prediction of performance
2. Planning training programs
Marker of training intensity
Choose a training HR based on LT
Oxygen uptake increases in a (____) fashion during incremental exercise until (___) is reached.
linear, VO2 max
Respiratory exchange ratio (RER or R)
VCO2/VO2
In order for R to be used as an estimate of substrate utilization during exercise,
the subject must have reached steady state. This is important because only during steady-state exercise are the VCO2 and VO2 reflective of metabolic exchange of gases in tissues.
Low-intensity exercise (<30% VO2 max)
fats are primary fuel
High-intensity exercise (>70% VO2 max)
Carbohydrates are primary fuel
Crossover" concept
Describes the shift from fat to CHO metabolism as exercise intensity increases
Crossover occurs because of:
Recruitment of fast glycolytic muscle fibers (influx of calcium)
Increasing blood levels of epinephrine
McArdle's Syndrome
Cannot synthesize the enzyme phosphorylase, Inability to break down muscle glycogen, Also prevents lactate production
At low exercise intensities (~20% VO2 max)
High percentage of energy expenditure (~60%) derived from fat
However, total energy expended is low
Total fat oxidation is also low
At higher exercise intensities (~50% VO2 max)
Lower percentage of energy (~40%) from fat
Total energy expended is higher
Total fat oxidation is also higher
Prolonged, low-intensity exercise
Shift from carbohydrate metabolism toward fat metabolism, due to an increased rate of lipolysis
Interaction of Fat and CHO Metabolism During Exercise
Glycogen is depleted during prolonged high-intensity exercise
Reduced rate of glycolysis and production of pyruvate. Reduced Krebs cycle intermediates. Reduced fat oxidation.
2 sources of carbs during exercise
1. Muscle glycogen
2. Blood Glucose
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 during long-duration exercise
2 Sources of fat during exercise
1. Intramuscular triglycerides
2. Plasma FFA
Intramuscular triglycerides
Primary source of fat during higher intensity exercise (~60% VO2max)
Plasma FFA
From adipose tissue lipolysis via HSL
Triglycerides > glycerol + FFA
FFA converted to acetyl-CoA and enters Krebs cycle.
Primary source of fat during low-intensity exercise. Becomes more important as muscle triglyceride levels decline in long-duration exe
Lactate as a fuel source during exercise:
1. Can be used as a fuel source by skeletal muscle and the heart
Converted to acetyl-CoA and enters Krebs cycle.
2. Can be converted to glucose in the liver - Cori cycle
3. Lactate shuttle - Lactate produced in one tissue and transported to another
Cori Cycle
Lactate produced by skeletal muscle is transported to the liver. >
Liver converts lactate to glucose
Gluconeogenesis.>
Glucose is transported back to muscle and used as a fuel.
At rest:
the VO2 is approximately 3.5 ml/kg/min.
Which of the following groups of activities use energy derived predominantly from the ATP-PC system?
gymnastics vault, softball pitch, high jump
The upward drift of VO2 during steady state exercise is primarily due to
increasing body temperature.
The physiological factors that influence VO2max are
A) the delivery of oxygen to the muscle.
B) the uptake and use of oxygen by the muscle.
C) genetics and exercise training.
A factor that contributes to excess post exercise oxygen consumption is
resynthesis of creatine phosphate in muscle.
The rise in blood lactic acid concentration above the lactate threshold can occur due to
A) an increase in lactic acid production.
B) a decrease in lactic acid removal.
During low intensity exercise (i.e., <30% VO2max), the primary fuel source for muscle is
fats
In prolonged (3-4 hours), moderate-intensity exercise, there is an increased reliance on
blood sources of carbohydrate and fat
The shift from fat to carbohydrate metabolism is regulated by
the type of fiber recruited.
The primary determinant of plasma FFA oxidation during exercise is
the blood level of the fuel.
The RQ for fat is
equal to VCO2/VO2.
During the first hour of submaximal exercise, most of the carbohydrate metabolized comes from
muscle glycogen.
The mobilization of free fatty acids into the blood is inhibited by
lactic acid.
Fatigue results after depletion of carbohydrate stores due to the reduction
A) in the muscle concentration of pyruvic acid.
B) of Krebs cycle intermediates.
C) of Krebs cycle activity.
The portion of the oxygen debt that is responsible for the conversion of lactic acid to glycogen is around
20%
The Cori cycle describes:
the steps by which lactic acid is converted to glucose in the liver
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
Lactate Threshold
- Low muscle oxygen
- Accelerated glycolysis
- Recruitment of fast-twitch fibers
- Reduced rate of lactate removal
% of Energy Expenditure of Muscle Glycogen
Hour 1: 45%
Hour 3: 15%
% Energy Expenditure of Blood Glucose
Hour 1: 50%
Hour 3: 45%
% Energy Expenditure of Plasma FFA
Hour 1: 75%
Hour 3: 90%
% Energy Expenditure of Muscle Triglycerides
Hour 1: 100 %
Hour 3: 100%
Rest-to-Exercise Transitions 1:
ATP production increases immediately
Rest-to-Exercise Transitions 2:
Oxygen uptake increases rapidly
Reaches steady state within 1-4
minutes
After steady state is reached,
ATP requirement is met through
aerobic ATP production
Rest-to-Exercise Transitions 3:
Oxygen deficit
Means a lag in oxygen uptake at
the beginning of exercise
Suggests anaerobic pathways
contribute to total ATP
production
Rest-to-Exercise Transitions 4:
Initial ATP production through anaerobic pathways
ATP-PC system
Glycolysis
At steady state VO2,
ATP supply aerobically matches ATP demand
Excess post-exercise oxygen consumption (EPOC)
Terminology reflects that only ~20% elevated O2 consumption used to "repay" O2 deficit
Rapid" portion of O2 debt or EPOC (2 to 3 min post-exercise)
Resynthesis of stored PC
Replenishing muscle and blood O2 stores
Slow" portion of O2 debt or EPOC (>30 min post exercise)
Elevated heart rate and breathing = ^ energy need
Elevated body temperature = ^ metabolic rate
Elevated epinephrine and norepinephrine = ^ metabolic rate
Conversion of lactic acid to glucose (gluconeogenesis)
Why is EPOC greater following higher intensity exercise?
Higher body temperature
Greater depletion of PC
Greater blood concentrations of lactic acid
Higher levels of blood epinephrine and norepinephrine
Removal of Lactic Acid Following Exercise
70% of lactic acid is oxidized
Used as a substrate by heart and skeletal muscle
20% converted to glucose
10% converted to amino acids
(Lactic acid is removed more rapidly with light exercise in recovery)
First 1-5 seconds of exercise
ATP through ATP-PC system
Intense exercise longer than 5 seconds
Shift to ATP production via glycolysis
Events lasting longer than 45 seconds
ATP production through ATP-PC, glycolysis, and aerobic systems
During high-intensity, short-term exercise
the muscle's ATP production is dominated by the ATP-PC system.
high-intensity events lasting longer than forty-five seconds use a combination of
the ATP-PC system, glycolysis, and the aerobic system to produce the needed ATP for muscular contraction, with a 50%/50% (anaerobic/aerobic) contribution needed for exercise lasting between 2 and 3 minutes.
2 Physiological factors influencing VO2 max:
1. Maximum ability of the cardiorespiratory system to deliver oxygen to contracting muscle
2. Ability of muscles to take up the oxygen and produce ATP aerobically
Lactate Threshold
The point at which blood lactic acid suddenly rises during incremental exercise
Lactate threshold occurs in untrained at
50~60& VO2 max
Lactate threshold occurs in trained at
65-80% VO2 max
Onset of Blood Lactate Accumulation (OBLA)
The point (exercise intensity) at which blood lactate levels reach 4 mmol/L
Explanations for the Lactate Threshold
1. Low muscle oxygen
2. Accelerated glycolysis
3. Recruitment of fast-twitch muscle fibers
4. Reduced rate of lactate removal from the blood
Accelerated Glycolysis
NADH produced faster than it is shuttled into mitochondria
Excess NADH in cytoplasm converts pyruvic acid to lactic acid
Recruitment of fast-twitch muscle fibers
LDH isozyme in fast fibers promotes lactic acid formation
LDH in fast-twitch fibers
favors formation of lactic acid because it has a greater affinity for attaching to hydrogen to pyruvate >> leading to increase in lactate production
LDH in slow-twitch fibers
promotes the conversion of lactate to pyruvate >> leading to decrease in lactate
Practical Uses of the Lactate Threshold
1. Prediction of performance
2. Planning training programs
Marker of training intensity
Choose a training HR based on LT
Oxygen uptake increases in a (____) fashion during incremental exercise until (___) is reached.
linear, VO2 max
Respiratory exchange ratio (RER or R)
VCO2/VO2
In order for R to be used as an estimate of substrate utilization during exercise,
the subject must have reached steady state. This is important because only during steady-state exercise are the VCO2 and VO2 reflective of metabolic exchange of gases in tissues.
Low-intensity exercise (<30% VO2 max)
fats are primary fuel
High-intensity exercise (>70% VO2 max)
Carbohydrates are primary fuel
Crossover" concept
Describes the shift from fat to CHO metabolism as exercise intensity increases
Crossover occurs because of:
Recruitment of fast glycolytic muscle fibers (influx of calcium)
Increasing blood levels of epinephrine
McArdle's Syndrome
Cannot synthesize the enzyme phosphorylase, Inability to break down muscle glycogen, Also prevents lactate production
At low exercise intensities (~20% VO2 max)
High percentage of energy expenditure (~60%) derived from fat
However, total energy expended is low
Total fat oxidation is also low
At higher exercise intensities (~50% VO2 max)
Lower percentage of energy (~40%) from fat
Total energy expended is higher
Total fat oxidation is also higher
Prolonged, low-intensity exercise
Shift from carbohydrate metabolism toward fat metabolism, due to an increased rate of lipolysis
Interaction of Fat and CHO Metabolism During Exercise
Glycogen is depleted during prolonged high-intensity exercise
Reduced rate of glycolysis and production of pyruvate. Reduced Krebs cycle intermediates. Reduced fat oxidation.
2 sources of carbs during exercise
1. Muscle glycogen
2. Blood Glucose
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 during long-duration exercise
2 Sources of fat during exercise
1. Intramuscular triglycerides
2. Plasma FFA
Intramuscular triglycerides
Primary source of fat during higher intensity exercise (~60% VO2max)
Plasma FFA
From adipose tissue lipolysis via HSL
Triglycerides > glycerol + FFA
FFA converted to acetyl-CoA and enters Krebs cycle.
Primary source of fat during low-intensity exercise. Becomes more important as muscle triglyceride levels decline in long-duration exe
Lactate as a fuel source during exercise:
1. Can be used as a fuel source by skeletal muscle and the heart
Converted to acetyl-CoA and enters Krebs cycle.
2. Can be converted to glucose in the liver - Cori cycle
3. Lactate shuttle - Lactate produced in one tissue and transported to another
Cori Cycle
Lactate produced by skeletal muscle is transported to the liver. >
Liver converts lactate to glucose
Gluconeogenesis.>
Glucose is transported back to muscle and used as a fuel.