Terms in this set (21)
oxygen uptake and consumption (VO2)...at onset of exercise and...
increases rapidly, reaches a steady-state within 1-4 miutes
lag in oxygen uptake at beginning of exercise. suggests anaerobic pathways contribute to total ATP production. difference between O2 supply and O2 demand. occurs at onset of exercise. energy sources other than aerobic system provide ATP. [ATP], [Pi], NADH increase as energy needs increase
after steady state is reached, ATP requirement is met through...
aerobic and anaerobic ATP production But more ATP per glucose from aerobic pathway
energy demand=energy supply. oxygen consumption=energy needs of task. submaximal constant load exercise (work does not change)
excess post-exercise oxygen consumption (EPOC)
aka oxygen debt. increase VO2 for several minutes immediately after exercise.
fast portion of O2 debt
resynthesis of stored PCr. replacing muscle and blood O2 stores
slow portion O2 debt
increase heart rate and breathing, increase energy need
increase body temp, increase metabolic rate
increase epinephrine and norepinephrine, increase metabolic rate
conversion of lactic acid to glucose (gluconeogenesis)
metaobic response to short term high intesnity exercise
High-intensity, short-term exercise (2-20 seconds):
ATP production by ATP-PC system
Intense exercise longer than 20 seconds:
ATP production via anaerobic glycolysis
High-intensity exercise longer than 45 seconds:
ATP production by ATP-PC, glycolysis, and aerobic systems
NOTE: all energy systems function at ALL times!
Energy systems work on a continuum
:not an abrupt but gradual shift
Metabolic response to prolonged exercise
Exercise longer than 10 minutes:
ATP production primarily from aerobic metabolism.
steady-state oxygen uptake can generally be maintained
Prolonged exercise in a hot/humid environment or at high intensity:
steady state not achieved or not maintained
upward drift in oxygen uptake over time
metabolic response to incremental exercise
Oxygen uptake increases linearly until VO2max is reached
no further increase in VO2 with increase work rate (intensity)
Physiological factors influencing VO2max:
Ability of cardiorespiratory system to deliver oxygen to muscles
Ability of muscles to use oxygen and produce ATP aerobically
The point at which blood lactic acid suddenly rises during incremental exercise
Also called the anaerobic threshold. Practical uses in prediction of performance and as a marker of exercise intensity
mechanism of lactate threshold
low muscle oxygen)
Accelerated glycolysis relative to aerobic metabolism
(recruitment of fast-twitch muscle fibers)
Reduce rate of lactate removal from the blood
sources of fuel during exercise
plasma FFA (from adipose tissue lipolysis) intramuscular (intra=within) triglycerides
small contribution to total energy production (~2%) may increase to 5-15% late in prolonged exercise
gluconeogenesis via the Cori cycle
Estimation of Fuel Utilization During Exercise
Respiratory exchange ratio (RER)=VCO2/Vo2
RER: indicates fuel utilization
0.70 =100% fat
0.85 =50% fat, 50% CHO
1.00 =100% CHO
CHO and fat use different amount of O2 (and produce different amounts of CO2) during oxidation
During steady-state exercise:
VCO2 and VO2 reflect CO2 production and O2 consumption at the cellular level
Exercise Intensity and Fuel Selection: at high and low intensities
Low-intensity exercise (<30% VO2max)
fats are primary fuel (ignore protein)
High-intensity exercise (>70% VO2max)
CHO are primary fuel (ignore protein). crossover concept.
The shift from fat to CHO as exercise intensity increases
Energy needs>ability to deliver fats and run aerobically
(recruitment of fast, muscle fibers)
Increase blood levels of epinephrine
Interaction of Fat and CHO Metabolism During Exercise
"Fats burn in a carbohydrate flame"
Glycogen (CHO) is depleted during prolonged high-intensity exercise
increase rate of glycolysis → decreasae production of pyruvate
→ decrease Kreb's cycle intermediates (substrate)
→ decrease fat oxidation (fats are metabolized in
Best exercise intensity for weight management
Low intensity exercise?
Greater proportion of fat used to perform exercise!
83% (low-intensity) vs. 42% (high-intensity)
But, total energy used is higher in high-intensity exercise-
Low intensity: 118 kcals from fat, 142 kcals total vs.
High intensity: 112 kcals from fat, 264 kcals total
Important feature is total energy expenditure
Remember-kcals during recorvery!
burn more calories during recovery
Breaks glucose backbone from glycogen and adds phoshate
2 Pathways for activating phosphorylase
1. calmodulin activated by calcium released from sarcoplasmic reticulum
active calmodulin activates phosphorylase (this happens immediate at onset of exercise)
2. Epinephrine binding to receptor on muscle cell membrane results in formation of cyclic AMP
cyclic AMP activates phosphorylase
Cannot synthesize the enzyme phosphorylase
Due to 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 (insuffient ATP to keep exercising)
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