Exercise Metabolism

Question 1

During the transition from light to moderate exercise, why does O2 consumption not increase simultaneously?

Answer 1

Anaerobic sources play a role in ATP production at the beginning of exercise

Question 2

What is the order of energy system recruitment for ATP production during exercise?

Answer 2

ATP-PC, Glycolysis, Aerobic energy production

Question 3

What is oxygen deficit?

Answer 3

The difference between oxygen uptake in the first few minutes of exercise, and an equal time period after steady state has been obtained.

Question 4

Why are anaerobic energy systems dominant during the first few minutes of exercise?

Answer 4

Because oxygen uptake is insufficient until it reaches steady state

Question 5

Why do trained individuals reach a steady state VO2 faster than untrained individuals?

Answer 5

Result of an increased bioenergetic capacity, aka aerobic ATP production is active earlier resulting in a lower lactate production

Question 6

What is oxygen debt?

Answer 6

elevated oxygen levels (above resting) post exercise

Question 7

What is the difference between rapid and slow oxygen debt?

Answer 7

Rapid oxygen debt is characterized as the lack of oxygen 2-3 minutes post exercise while slow oxygen debt is greater than 30 minutes

Question 8

What does rapid oxygen debt represent?

Answer 8

The oxygen required to resynthesize stored ATP and PC (~20% of oxygen debt)

Question 9

What does slow oxygen debt represent?

Answer 9

The portion of oxygen debt that is due to the oxidative conversion of lactate to glucose in the liver
(~80%)

Question 10

What is EPOC?

Answer 10

Excess post exercise oxygen consumption

Question 11

In comparison to moderate intensity exercise, why is EPOC higher in high intensity exercise?

Answer 11

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

Question 12

What is the optimal light exercise intensity to aid in lactate removal post exercise?

Answer 12

40-50%VO2 max (untrained)

Question 13

When do all 3 energy systems get utilized?

Answer 13

In events longer than 45 seconds

Question 14

The ATP-PC system is dominant in exercise lasting:

Answer 14

2-20 seconds

Question 15

Anaerobic glycolysis is the dominant energy system :

Answer 15

In high intensity events more than 20 seconds and less than 45

Question 16

A 50/50 split between anaerobic and aerobic energy systems is seen:

Answer 16

In high intensity events spanning between 2-3 minutes

Question 17

Steady state oxygen uptake can usually be maintained during moderate exercise. What are the two exceptions?

Answer 17

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

Question 18

What are the primary causes for upward drift of oxygen consumption during exercise?

Answer 18

1) increased body temp
2) rising blood levels of epi and norepi

(due to an increase metabolic rate)

Question 19

At what percent of VO2 max is lactate threshold usually reached?

Answer 19

50-60 untrained, 65-80 trained

Question 20

What are some of the possible explanations as to why there is a sudden rise in blood lactate concentration during incremental exercise?

Answer 20

1) Low muscle oxygen
2) accelerated glycolysis due to epinephrine
3) recruitment of fast muscle fibers
4) reduced rate of lactate removal

Question 21

What is the respiratory exchange ratio?

Answer 21

ratio between the volume of CO2 produced (VCO2) and the volume of oxygen produced (VO2)

Question 22

What is a limitation of using R to estimate substrate utilization during exercise?

Answer 22

It is only reflective of substrate utilization during steady-state exercise

Question 23

What is the amount of energy released per 1 L of O2 when carbohydrates and fats are burned?

Answer 23

Carbohydrates: 5.0 kcal when carbs alone are used
Fats: 4.7 kcal when fats alone are used
6%difference

Question 24

What are some of the factors that determine whether fat or carbohydrates are the primary fuel source burned?

Answer 24

1) diet
2) intensity and duration of workout
3) whether the subject is endurance trained

Question 25

What fuel source is the primary fuel source during low intensity exercise (~30% VO2 max)?

Answer 25

Fats

Question 26

What is the crossover point?

Answer 26

Where the body switches from using fats as the primary fuel source to using carbohydrates

Question 27

What causes the body to switch from using fats to carbohydrates?

Answer 27

1) Recruitment of fast fibers

2) Increased blood levels of epinephrine

Question 28

Why are fast fibers better at breaking down carbs than fats?

Answer 28

Fast fibers have lots of glycolytic enzymes (carb breakdown) but few mitochondrial and lipolytic enzymes (fats)

Question 29

What are the primary storage sites for carbohydrates in the body?

Answer 29

Liver glycogen, glucose in blood and extracellular fluid, muscle glycogen

Question 30

What are the primary storage sites for usable fat in the body?

Answer 30

Plasma FFA (from adipose tissue lipolysis) and intramuscular triglycerides

Question 31

How does protein utilization change as exercise duration increases?

Answer 31

Less than 1 hour=less than 2% of fuel used comes from protein
Prolonged (3-5 hrs)= 5-10% during final minutes of prolonged work

Question 32

What are some practical uses of lactate threshold?

Answer 32

1) Prediction of performance

2) Planning of training programs : marker of training intensity and choosing of heart rate goals

Question 33

What is a limitation of using muscle glycogen as a fuel source?

Answer 33

It does not release glycogen back into the blood, only available for that muscle to use

Question 34

What mechanism allows blood lactate to be used as a fuel source?

Answer 34

The Cori cycle