1. Macronutrient Metabolism in Exercise and Training
Chapter 5

2. Fuel for Exercise
The fuel mixture that powers exercise generally depends on:
The intensity of effort
The duration of effort
The exerciser’s fitness status
The exerciser’s nutritional status

3. Bioenergetics Cells need constant supply of ATP
Minimal amounts stored for cellular processes
Intramuscular
Muscular contraction-exercise
Constant, large supply

4. Bioenergetics Formation of ATP (3 metabolic pathways)
1. Phosphocreatine (PC) breakdown
ATP-PC system (phosphagen system)
2. Degradation of glucose and glycogen
Glycolysis (Glycolytic system)
3. Oxidative phosphorylation
Tricarboxylic cycle, Krebs cycle

5. Bioenergetics Anaerobic pathways (do not involve O2) Aerobic pathway
1. ATP-PC breakdown
2. Anaerobic glycolysis
Aerobic pathway
Requires O2
2. Aerobic glycolysis
3. Oxidative phosphorylation

6. Bioenergetics ATP-PC ATP-PCr (30 sec) Activities (examples)
Sprints (< 30 sec)
High jumping
Weight lifting

7. Bioenergetics Anaerobic Glycolysis – Examples:
Lactic acid system (20 or 30 sec to 120 sec)
Intermediate in duration
Examples:
Middle distance running
Swimming
Basketball

8. Bioenergetics High intensity exercise – 2 minutes Aerobic sources
ATP-PCr (30 sec)
Lactic acid systems ( sec)
Provide 50% of the energy
Aerobic sources

9. Aerobic Energy Longer duration Requires a steady energy supply
Examples:
Marathon running
Distance swimming or cycling
Jogging, hiking, or backpacking
Little or no lactic acid buildup

10. Energy Continuum

11. Relative Aerobic & Anaerobic Contributions
Crossover concept

12. Sources of Energy for ATP Synthesis
Sources of energy for ATP synthesis include:
Liver and muscle glycogen
Triacylglycerols within adipose tissue and active muscle
Amino acids within skeletal muscle donate carbon skeletons

13. Carbohydrate Use During Exercise
Intense anaerobic exercise
Muscle glycogen
Blood glucose
Sustained high levels - aerobic exercise.
Glycogen stores
Blood glucose –
Glycogen breakdown - released from liver

14. Macronutrient Contributions

15. Intense Exercise Change in hormone release Stimulation Epinephrine
Norepinephrine
Glucagon
Decreased insulin release
Stimulation
Glycogen phosphorylase - glycogenolysis
p157

16. Intense Exercise Early stages Later stages Stored muscle glycogen
Glycogenolysis of liver stores
Blood glucose
Blood glucose can supply 30%

17. 300 g gly in leg muscles, 100 g in liver
300 g gly in leg muscles, 100 g in liver. Fat stored in adipose cells in muscle fibers and close to mito.

18. Moderate and Prolonged Exercise
As exercise continues
Glucose from the liver becomes major contributor (as muscle glycogen falls; about 2-3 hrs)
Fat use increases

19. CHO & Exercise
Sharp uptake of blood glucose during initial stage of exercise, continue to increase as exercise progresses, faster supply of energy

20. Glycogen Depletion Blood glucose levels fall.
Level of fatty acids in the blood increases.
Proteins provide an increased contribution to energy.
Exercise capacity progressively decreases.

21. Moderate and Prolonged Exercise
Progressive decrease blood glucose, increase fat metabolism
fat metabolism increases with similar exercise when glycogen loaded
protein use for energy remains higher with glycogen depletion
After 2 h exercise capacity decreases to 50% of max, glycogen depleted state.

22. Fatigue “hitting the wall” Results Fall in muscle/liver glycogen
CNS used blood glucose as energy (central fatigue)
Increased fat metabolism
Fat provides energy at a slower rate
Slower rate figure 5.5 FA mobilization and transport, and breakdown takes longer

23. Trained Muscle Trained muscle So, trained individuals
Increased ability to produce ATP (inc. mitochondrial volume)
Increased blood supply (capillary density)
Increased glycogen storage
So, trained individuals
Maintain a higher work rate
Maintain that workrate for longer periods of time

24. Dietary Influence Condition 1 (Low carb) Condition 2 (normal)
Normal caloric intake – 3 days
CHO 5%
Lipid 95%
Condition 2 (normal)
Recommended % CHO, Fat, Pro
Condition 3 (high carb)
CHO 82%

25. Dietary Influence

26. Influence of Diet A carbohydrate-deficient diet
Rapid depletion of muscle and liver glycogen.
Low carbohydrate levels
Intensity decreases to level determined by how well the body mobilizes and oxidizes fat.
So, this diet reduces performance

27. Fat as an Energy Substrate
Fat supplies about 50% of the energy
Light and moderate exercise.
Stored fat
Important during the latter stages of prolonged exercise (greater than 2 hours)

28. Caloric Equivalents
CHO and fat contribute equally during moderate exercise, fat gradually increases as glycogen is depleted

29. Sources of Fat During Exercise
Fatty acids released from adipocytes
Delivered to muscles as FFA bound to plasma albumin
Circulating plasma triacylglycerol
Very low-density lipoproteins
Chylomicrons
Triacylglycerol
Within active muscle itself

30. Lipolysis Hormones activate lipase.
These hormones are secreted more during exercise.
Epinephrine, Nor-epinephrine, GH
Mobilization of FFAs from adipose tissue
Trained muscle has an increased ability to utilize fat due to the higher volume of mitochondria

31. Exercise Training Regular aerobic exercise:
Increases the ability to oxidize long-chain fatty acids
Improves the uptake of FFAs
Increases muscle capillary density
Increases size and number of muscle mitochondria
SO, at the same workload, after training
Fat metabolism is up and CHO metabolism is down
Same relative workload (% max), CHO and Fat utilization is the same
Goals of endurance training

32. Exercise Training
After training, energy from fat oxidation increases following aerobic training

33. Protein Use During Exercise
Carbohydrate-depleted state
Causes significant protein catabolism.
Protein utilization rises
Endurance
Resistance-type exercise.

34. Protein Use During Exercise
Greater use as energy fuel than previously thought
Nutritional status
Intensity of exercise training or competition.
Duration of exercise
Certain AAs, the branched-chain amino acids
Leucine, Iso-leucine and valine
Oxidized directly in skeletal muscle

35. Exercise and Protein Metabolism
Lemon 10.3 maughan increase rates of muscle protein degradation, significant muscle damage with exercise, especially if there is a significant eccentric component.

36. Protein Use During Exercise
Branched-chain amino acids
Oxidized in skeletal muscle not the liver.
Leucine, isoleucine, valine
Make up 1/3 skeletal muscle
Important in protein synthesis
Seem to be oxidized during longer term endurance exercise
side-chains that are non-linear. These are leucine, isoleucine and valine. The combination of these three essential amino acids make up approximately 1/3 of skeletal muscle in the human body, and play an important role in protein synthesis. BCAA’s are currently used clinically to aid in the recovery of burn victims, as well as for supplementation for strength athletes.

37. Exercise and Protein Metabolism
Lemon 10.6 maughan maybe because most of energy is from anaerobic metabolism and muscle glycogen

38. Exercise and Protein Metabolism
Endurance exercise – increased protein need as neg balance occurs

39. Exercise and Protein Metabolism
The data indicate that both endurance and strength athletes need more protein than sedentary