Chapter 69: Exercise Metabolism

Question 1

Two major types of exercise

Answer 1

• Aerobic

- Anaerobic

Question 2

Aerobic exercise

Answer 2

• Involves prolonged, low intensity exercise (cross-country running or swimming)

Question 3

Anaerobic exercise

Answer 3

• Requires high intensity work of short duration

Question 4

Energy for anaerobic exercise

Answer 4

• Derived rapidly by utilizing substrates from within the muscle

Question 5

Energy for aerobic exercise

Answer 5

• Derived from sources such as fat in adipose tissue or liver glycogen

Question 6

Three major energy sources for exercise

Answer 6

• Phosphagen system
• Glycogen-lactate system
• Aerobic system

Question 7

Phosphagen system

Answer 7

• Integrated pools of ATP and creatine phosphate provide maximal muscle power

Question 8

ATP in the phosphagen system

Answer 8

• Sufficient for maximal muscle power for short bursts (about 4s)
• New ATP must be formed continuously (no ox needed)
• Phosphocreatine reconstitutes a continuous supply of ATP

Question 9

High-energy phosphate bond of creatine phosphate

Answer 9

• Has more energy than the bond of ATP

- Creatine phosphate can provide enough energy to reform the high-energy bond within a fraction of a second

Question 10

Creatine phosphate

Answer 10

• High-energy compound
• Stored in muscle cells
• Activated instantly, used to replenish ATP rapidly

Question 11

Creatine phosphate is made in

Answer 11

• Made in muscle from creatine

- Formed in kidney and liver from amino acids

Question 12

Creatine phosphate storage

Answer 12

• Not enough is stored or made in the muscle to sustain ATP for more than a few minutes (limited capacity)

Question 13

Glycogen/lactate system

Answer 13

• Energy production via anaerobic glycolysis (substrate level phosphorylation)
• Stored muscle glycogen converted to g-6-p and utilized for energy

Question 14

Muscle glycogen becomes lactate (anaerobic) causing

Answer 14

• Metabolic acidosis

- Low pH causes fatigue (PFK-1Iis inhibited)

Question 15

The flux through the glycolytic pathway can increase by 1000-fold with

Answer 15

• The onset of sudden exercise

Question 16

Glycogen/lactate system can form ATP molecules

Answer 16

• 2.5x as rapidly as oxidation in mitochondria

- More than ten times less efficient on a molar basis

Question 17

Aerobic system

Answer 17

• Utilization of pyruvate from glucose or other substrates
• Krebs cycle and oxidative phosphorylation
• Required for prolonged activity

Question 18

Aerobic system provides

Answer 18

• 95% energy at rest

Question 19

Preferred substrate for exercising muscle

Answer 19

• Glucose

Question 20

Sources of glucose for aerobic and anaerobic energy production

Answer 20

• Intramuscular glycogen stores

- Plasma glucose pool

Question 21

Plasma glucose pool during muscle activity

Answer 21

• Supply, transport and phosphorylation
• Increased muscle GLUT 4 expression with exercise
• Contraction stimulated glucose uptake

Question 22

Energy substrates for exercise

Answer 22

• Short duration, intense muscle activity = muscle glycogen then blood glucose

Question 23

Depletion of glycogen reserves during exercise causes

Answer 23

• Switch from carbohydrate oxidation to lipolysis
• Activation of FA oxidation enzymes
• Inhibition of FA synthesis enzymes

Question 24

Intake of 30-60 gm CHO/hour during strenuous endurance activity

Answer 24

• Delays fatigue by 30-60 minutes
• Maintains plasma glucose levels and high rates of glucose oxidation
• Spares hepatic glycogen reserves

Question 25

Metabolic activity during exercise

Answer 25

• Increased glucose delivery to muscle
• Lactate from anaerobic exercise is removed (will inhibit PFK-1
• Note also FA and ketone body use by muscle

Question 26

The increased uptake of glucose from the blood by exercising muscle may benefit the diabetic patient

Answer 26

• Even if insulin is not working

- Recall how obesity can lead to type II DM

Question 27

Major fuel for prolonged, low-intensity activity

Answer 27

• Fat
• Majority of stored energy in the body (concentrated)
• TAGs broken down to free FAs and glycerol

Question 28

Fatty acids travel to muscle cells and can be converted to

Answer 28

• Acetyl-SCoA in the mitochondria

- Generates lots of ATP (2x as much as CHO and protein metabolism)

Question 29

Marathon running fat consumption

Answer 29

• 50:50 FA:CHO

Question 30

Elevated hormones during exercise

Answer 30

• Glucagon
• Cortisol
• Adrenaline
• Noradrenaline
• Growth hormone

Question 31

Depressed hormones during exercise

Answer 31

• Insulin (hormone-sensitive lipase will be on)

Question 32

The conversion of liver glycogen to glucose

Answer 32

• Promoted during exercise
• Raises plasma glucose levels
• Glucose is available for uptake by the exercising muscle cells

Question 33

No glucose uptake by fat during exercise because

Answer 33

• Requires insulin (depressed during exercise)

- Recall enzymes of glycogenolysis and glycogenesis

Question 34

Carbohydrate loading

Answer 34

• Consumption of carbs post-workout to replenish depleted stores (oxidation of carbs is an energy source)

Question 35

Benefits of carbohydrate loading for exercise

Answer 35

• Typically better for events lasting longer than 90 minutes
• Maximizes muscle glycogen stores and delays onset of fatigue
• Tapering of exercise while increasing CHO intake
• Increases stores by 50-85%

Question 36

Most effective exercise for burning calories

Answer 36

• Combination of resistance exercise and aerobic exercise

Question 37

Maintenance of lean muscle tissue is a result of

Answer 37

• Increased mitochondrial content

Question 38

Enhanced insulin action of regular exercise seen mostly in

Answer 38

• Moderate intensity exercise (brisk walking)

- Aiming for 5-10% weight loss is the cornerstone of management of type II DM