Exercise Metabolism Flashcards
During the transition from light to moderate exercise, why does O2 consumption not increase simultaneously?
Anaerobic sources play a role in ATP production at the beginning of exercise
What is the order of energy system recruitment for ATP production during exercise?
ATP-PC, Glycolysis, Aerobic energy production
What is oxygen deficit?
The difference between oxygen uptake in the first few minutes of exercise, and an equal time period after steady state has been obtained.
Why are anaerobic energy systems dominant during the first few minutes of exercise?
Because oxygen uptake is insufficient until it reaches steady state
Why do trained individuals reach a steady state VO2 faster than untrained individuals?
Result of an increased bioenergetic capacity, aka aerobic ATP production is active earlier resulting in a lower lactate production
What is oxygen debt?
elevated oxygen levels (above resting) post exercise
What is the difference between rapid and slow oxygen debt?
Rapid oxygen debt is characterized as the lack of oxygen 2-3 minutes post exercise while slow oxygen debt is greater than 30 minutes
What does rapid oxygen debt represent?
The oxygen required to resynthesize stored ATP and PC (~20% of oxygen debt)
What does slow oxygen debt represent?
The portion of oxygen debt that is due to the oxidative conversion of lactate to glucose in the liver
(~80%)
What is EPOC?
Excess post exercise oxygen consumption
In comparison to moderate intensity exercise, why is EPOC higher in high intensity exercise?
1) Heat production and body temp are higher
2) PC is depleted to a greater extent and more O2 is required for its resynthesis
3) Higher blood lactate levels mean more O2 is required for lactate conversion to glucose in gluconeogenesis
4) Epi and norepi levels are much higher
What is the optimal light exercise intensity to aid in lactate removal post exercise?
40-50%VO2 max (untrained)
When do all 3 energy systems get utilized?
In events longer than 45 seconds
The ATP-PC system is dominant in exercise lasting:
2-20 seconds
Anaerobic glycolysis is the dominant energy system :
In high intensity events more than 20 seconds and less than 45
A 50/50 split between anaerobic and aerobic energy systems is seen:
In high intensity events spanning between 2-3 minutes
Steady state oxygen uptake can usually be maintained during moderate exercise. What are the two exceptions?
1) Prolonged exercise in in hot/humid environment will cause upward drift
2) continuous exercise at high relative work rate (>75%VO2 max) results in slow rise in uptake
What are the primary causes for upward drift of oxygen consumption during exercise?
1) increased body temp
2) rising blood levels of epi and norepi
(due to an increase metabolic rate)
At what percent of VO2 max is lactate threshold usually reached?
50-60 untrained, 65-80 trained
What are some of the possible explanations as to why there is a sudden rise in blood lactate concentration during incremental exercise?
1) Low muscle oxygen
2) accelerated glycolysis due to epinephrine
3) recruitment of fast muscle fibers
4) reduced rate of lactate removal
What is the respiratory exchange ratio?
ratio between the volume of CO2 produced (VCO2) and the volume of oxygen produced (VO2)
What is a limitation of using R to estimate substrate utilization during exercise?
It is only reflective of substrate utilization during steady-state exercise
What is the amount of energy released per 1 L of O2 when carbohydrates and fats are burned?
Carbohydrates: 5.0 kcal when carbs alone are used
Fats: 4.7 kcal when fats alone are used
6%difference
What are some of the factors that determine whether fat or carbohydrates are the primary fuel source burned?
1) diet
2) intensity and duration of workout
3) whether the subject is endurance trained
