Exercise Physiology Ch. 4
Terms in this set (43)
1 ; 4
In the transition from rest to light or moderate exercise, oxygen uptake increases rapidly, generally reaching a steady state within _ to _ minutes.
What is oxygen deficit?
applies to the lag in oxygen uptake at the beginning of exercise.
Anaerobic ; aerobic
The failure of oxygen uptake to increase instantly at the beginning of exercise suggests that____ pathways contribute to the overall production on ATP early in exercise. After a steady state is reached, the body's ATP requirement is met via ____ metabolism.
(also called excess post-exercise oxygen consumption [EPOC]) is the O2 consumption above rest following exercise. Term used by A.V. Hill
Elevated Body, temperature,
Several factors contribute to the EPOC. First, some of the O2 consumed early in the recovery period is used to resynthesize stored PC in the muscle and replace O2 stores in both muscle and blood. Other factors that contribute to the "slow" portion of the EPOC include and _____ _____ _____, O2 required to convert lactate to glucose (gluconeogenesis), and elevated blood levels on epinephrine and norepinephrine
What is EPOC?
Excess post-exercise oxygen consumption (EPOC)
Terminology reflects that only ~20% elevated O2 consumption used to "repay" O2 deficit
Describe the two parts of oxygen debt?
"Rapid" portion of O2 debt
Resynthesis of stored PC
Replenishing muscle and blood O2 stores
"Slow" portion of O2 debt
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)
True or False? and why?
EPOC is Greater Following Higher Intensity Exercise.
Higher body temperature
Greater depletion of PC
Additional O2 required for resynthesis
Greater blood concentrations of lactic acid
Greater level of gluconeogenesis
Higher levels of blood epinephrine and norepinephrine
What is the classical theory?
*Majority of lactic acid converted to glucose in liver
-70% of lactic acid is oxidized
Used as a substrate by heart and skeletal muscle
-20% converted to glucose
-10% converted to amino acids
True or False?
Lactic acid is removed more rapidly with light exercise in recovery.
Optimal intensity is ~30-40% VO2 max
During _____ _____, short-term exercise (i.e., 2 to 20 seconds), the muscle's ATP production is dominated by the ATP-PC system.
Intense exercise lasting more than 20 seconds relies on ______ glycolysis to produce much of the needed ATP.
70% anaerobic/30% aerobic at 60 seconds
50% anaerobic/50% aerobic at 2 minutes
The energy to perform prolonged exercise (i.e., more than 10 minutes) comes primarily from ____ metabolism.
A _____ _____ oxygen uptake can generally be maintained during prolonged, moderate-intensity exercise. However, exercise in a hot/humid environment or exercise at a high relative work rate results in an upward "drift" in oxygen consumption over time; therefore, a steady state is not obtained in these types on exercise due to body temperature and rising epinephrine and norepinephrine
____ _____ increases in a linear fashion during incremental exercise until VO2 max is reached.
Lactic Threshold; Anaerobic threshold
The point at which there is a sudden increase in blood lactate concentration during incremental (graded) exercise is termed the ______ _____ also called _____ ______
-Appears at ~50-60% VO2 max in untrained subjects
-At higher work rates (65-80% VO2 max) in trained subjects
-Blood lactate levels reach 4 mmol/L
What does "Physiological ceiling" do?
Deliver oxygen to muscle that is affected by genetics and training
What Physiological factors influence VO2 max?
-Maximum ability of cardiorespiratory system to deliver oxygen to the muscle
-Ability of muscles to use oxygen and produce ATP aerobically
What is hypoxia?
Low muscle oxygen
What is accelerated glycolysis?
NADH produced faster than it is shuttled into mitochondria
Excess NADH in cytoplasm converts pyruvic acid to lactic acid
Explanations for the Lactate Threshold
Recruitment of fast-twitch muscle fibers
LDH isozyme in fast fibers promotes lactic acid formation
Reduced rate of lactate removal from the blood
What are the Practical Uses of the Lactate Threshold?
*Prediction of performance :
Combined with VO2 max
*Planning training programs
Marker of training intensity
Choose a training HR based on LT
Does Lactate Cause Muscle Soreness?
*Lactate production in commonly believed to cause muscle soreness.
-Delayed-onset muscle soreness (DOMS)
24-48 hours after exercise
-Lactate removal is rapid (within 60 minutes) following exercise
-Power athletes should experience DOMS after every work out
-Muscle soreness is rare following routine workout
What does cause muscle soreness?
Microscopic injury to muscle fibers leads to inflammation
respiratory exchange ratio (R)
is the ratio of carbon dioxide produced to the oxygen consumed (VCO2/VO2).
In order for R to be used as an estimate of substrate utilization during exercise, the subject must have reached _____ _____. This is important because only during steady-state exercise are the VCO2 and VO2 reflective of metabolic exchange of gases in tissues.
The caloric equivalent for oxygen is ____ kcal/L when fat alone is used and ___ kcal/L when carbohydrate alone is used, about a 6% difference.
(<30% VO2 max)
Fats are primary fuel
(>70% VO2 max)
Carbohydrates are primary fuel
What is the " crossover concept" ?
Describes the shift from fat to CHO metabolism as exercise intensity increases
Recruitment of fast muscle fibers
Increasing blood levels of epinephrine
*A Genetic Error in Muscle Glycogen Metabolism
-Cannot synthesize the enzyme phosphorylase due to a gene mutation
-Inability to break down muscle glycogen
-Also prevents lactate production
-Blood lactate levels do not rise during high-intensity exercise
-Patients complain of exercise intolerance and muscle pain
Is Low-Intensity Exercise Best for Burning Fat?
*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
Breakdown of triglycerides > glycerol + FFA
By enzymes called lipases
Stimulated by rising blood levels of epinephrine
True or False
"Fats burn in the flame of carbohydrates"
Is this True or False?
The depletion of muscle and blood carbohydrate stores contributes to fatigue
Ingestion of _____ can improve endurance performance
During submaximal (<70% VO2 max), long-duration (>90 minutes) exercise
30-60 g of carbohydrate per hour are required
May also improve performance in shorter, higher intensity events
Primary source of carbohydrate during high-intensity exercise
Supplies much of the carbohydrate in the first hour of exercise
From liver glycogenolysis
Primary source of carbohydrate during low-intensity exercise
Important during long-duration exercise
As muscle glycogen levels decline
What are some sources of fat during exercise?
*Intramuscular triglycerides- Primary source of fat during higher intensity exercise
From adipose tissue lipolysis
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 exercise
What are some sources of proteins during exercise?
*Proteins broken down into amino acids
-Muscle can directly metabolize branch chain amino acids and alanine
-Liver can convert alanine to glucose
*Only a small contribution (~2%) to total energy production during exercise
-May increase to 5-10% late in prolonged-duration exercise
-Enzymes that degrade proteins (proteases) are activated in long-term exercise
Lactate as a Fuel Source During Exercise
*Can be used as a fuel source by skeletal muscle and the heart
-Converted to acetyl-CoA and enters Krebs cycle
*Can be converted to glucose in the liver
Lactate produced in one tissue and transported to another
The Cori Cycle: Lactate as a Fuel Source
-Lactate produced by skeletal muscle is transported to the liver
-Liver converts lactate to glucose
-Glucose is transported back to muscle and used as a fuel
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