1. Metabolic System and Exercise
EXS 558
Lecture #4
September 21, 2005

2. Review Questions #1-3 What is the primary role of hormones?
Maintain homeostasis
Most hormone secretion is modulated through what biological process?
Negative Feedback
Why is this process effective?
Self-limiting

3. Review Question #4
Name three mechanisms which affect circulating concentrations of hormones?
1.) exercise (physical stress)
2.) psychological stress
3.) fluid volume stress

4. Review Question #5
Exercise can induce alterations in the endocrine system other than changing the circulating concentrations of hormones. Give an example of how this is possible.
Down-Regulation: the # of hormone receptors is decreased to reduce the possibility of contact between the “lock and key”

5. Review Question #6
What is one of the major differences between steroid and peptide hormones?
Steroid hormones are lipid soluble allowing them to pass through the cell membrane to their intracellular receptors, while peptide hormones react with receptors housed in the cell membrane

6. Review Questions #7, 8 TRUE/FALSE TRUE/FALE
A single training session has been shown to decrease peripheral testosterone levels above resting levels
TRUE/FALE
Type of training program affects circulating testosterone levels

7. Review Question #9
What would be the expected testosterone response to a 10 mile run (~70 minutes)?
a.) no response, endurance activity has no effect
b.) ↑ circulating testosterone levels
c.) ↓ circulating testosterone levels
d.) first it increases and then decreases

8. Review Question #10
Which of the following has the LEAST effect on influencing a growth hormone response?
a.) sleep
b.) nutrition
c.) exercise
d.) environment

9. Literature Review Techniques
SUNY Cortland Memorial Library Databases
Search Options
1.) By Subject: Exercise Science & Sport Studies
a.) MEDLINE
b.) SportDiscus
c.) Physical Education Index
2.) Fulltext Database (.PDF available online)

10. Literature Review Techniques (continued)
Find IT Button
Reference  Save Citation Information (APA)
Google Scholar
Cortland ESSS Librarian

11. Literature Review Techniques (continued)
Search for a recent REVIEW article close to your topic, if possible
Print online abstracts of all articles you may include within your review of literature
Use ILL early  it takes time to receive articles

12. Metabolic System & Exercise

13. Aerobic vs. Anaerobic Training
Aerobic (endurance) training leads to
w Improved blood flow, and
w Increased capacity of muscle fibers to generate ATP
Metabolic and Morphological Changes
Anaerobic training leads to
w Increased muscular strength, and
w Increased tolerance for acid-base imbalances during highly intense effort.
Metabolic Changes

14. Energy Systems Phosphagen Energy System (ATP-PC)
Cytoplasm
High-intensity: Up to 30 seconds
Glycolytic Energy System
High-intensity: 1-3 minutes
Oxidative Energy System
Mitochondria
Activity > 3 minutes

15. ATP
Adenosine triphosphate (ATP) common currency of useful (chemical) energy used by cells
Principle function of ATP
Energize synthesis of important cellular components
Energize muscular contractions
Synthesis of organic molecules used for structure and function
Energize active transport

16. ATP (continued) Energy released from ATP caused by ATPase
ATP + water  ADP + Pi + 7,000 cals/mol
1 mole of energy of ATP stores 12,000 cals, however, the real function of ATP is to transfer energy!
- energy stored in ATP will sustain life for about 90 seconds

18. ATP-PC Energy Source ATP-PC (Phosphocreatine) stored within the muscle
Immediate use
PC is major storage depot for energy (13,000 cals/mol)
It transfers phosphate group to ADP, so it can become ATP again
Catabolic breakdown of food substrate leads to synthesis of ATP
When subjects in study are brought to maximal exertion levels, ATP in muscles has not dropped much, but PC levels are way down

19. ATP-PC Energy Source (continued)
PC supply exhausted in ~30 seconds
PC levels decline rapidly during intense exercise (sprinting)
Resynthesis of PC
½ recovered in seconds
Last ½ may take up to 20 minutes
Most replenished within 3 minutes
Implications for workout design

20. ATP and PC During Sprinting

21. Glucose Breakdown and Synthesis
Glycolysis—Breakdown of glucose; may be anaerobic or aerobic
Glycogenesis—Process by which glycogen is synthesized from glucose to be stored in the liver
Glycogenolysis—Process by which glycogen is broken into glucose-1-phosphate to be used by muscles

22. Breakdown of Sugar (Glycolysis)
10 step pathway leads to synthesis of 2 pyruvate molecules and net production of 2 ATP molecules (or 3)
All reactions in cytosol and none require O2
Fate of pyruvate depends on O2
If inadequate available (anaerobic), pyruvate converted to lactate
If enough O2, converted to acetyl-CoA

23. Breakdown of Sugar (Glycolysis)
Where does the glucose come from?
From the blood (1) through CHO digestion or (2) from the breakdown of glycogen in the liver
From glycogen broken down in the muscle
Gluconeogenesis = process of metabolizing glycogen into glucose
Glycogen metabolized = 3 ATP
Glucose metabolized = 2 ATP

24. Role of Lactic Acid
Nociceptors (pain receptors) are sensitive to changes in the cellular H+ levels
↑ lactic acid
interfere with production of ATP
Hinder binding of calcium to troponin (ECC)
*The combined actions of the ATP-PC and glycolytic systems allow muscles to generate force in the absence of oxygen; thus these two energy systems are the major energy contributors during the early minutes of high-intensity exercise.

26. Oxidative Energy Source
w Relies on oxygen to breakdown fuels for energy
w Produces ATP in mitochondria of cells
w Can yield much more energy (ATP) than anaerobic systems
w Is the primary method of energy production during endurance events

27. Oxidative Production of ATP
1. Aerobic glycolysis—cytoplasm
2. Krebs cycle—mitochondria (byproduct = CO2)
3. Electron transport chain—mitochondria
1 molecule  39 ATP
Oxidative energy system primarily uses CHO and FAT but during periods of CHO and prolonged exercise significant amounts of protein can be metabolized

28. Aerobic Glycolysis & Electron Transport Chain

29. Krebs Cycle

30. Oxidation of Fat Lipolysis = breakdown of fat for energy
triglycerides metabolized into glycerol and 3 free fatty acids
Free fatty acids used as primary energy source
Free fatty acids enter the mitochondria and undergo β-oxidation
Energy production from 1 molecule of fatty acid (palmitic acid C16H32O2) yields 129 ATP

32. Protein Metabolism
w Body uses little protein during rest and exercise (less than 5% to 10%).
w Some amino acids that form proteins can be converted into glucose.
w The nitrogen in amino acids (which cannot be oxidized) makes the energy yield of protein difficult to determine.

33. Energy Source Interaction
ALL three sources will supply a portion of the needed energy for exercise at all times
One system will predominate depending on the intensity of the exercise

34. Oxidative Capacity Determined by:
Oxidative enzyme activity within the muscles
Fiber-type composition and # of mitochondria
Oxygen availability and uptake in lungs
Endurance Training
What does training effect?

35. Review Ideas (continued)
w The ATP-PCr and glycolytic systems produce small amounts of ATP anaerobically and are the major energy contributors in the early minutes of high-intensity exercise.
w The oxidative system uses oxygen and produces more energy than the anaerobic systems.
(continued)
w Carbohydrate oxidation involves glycolysis, the Krebs cycle, and the electron transport chain to produce up to 39 ATP per molecule of glycogen aerobically.

36. Review Ideas (continued)
w Fat oxidation involves b oxidation of free fatty acids, the Krebs cycle, and the electron transport chain to produce more ATP than carbohydrate, but it is O2-limited.
w Protein generally contributes little to energy production (less than 5%), and its oxidation is complex because amino acids contain nitrogen, which cannot be oxidized.
w The oxidative capacity of muscle fibers depends on their oxidative enzyme levels, fiber-type composition, how they have been trained, and oxygen availability.

37. Metabolic Adaptations to High Intensity Training
ATP-PC Energy System
No change to resting levels of ATP or PC
Resting [ ] of enzymes may be positively altered
Causes activity of ↑ creatine kinase and myokinase
ADP + ADP  ATP + AMP
AMP leaves muscle and acts as signal to slow down glycolysis
Parra et al. (2000)
2 weeks of daily sprint training
↑ elevation of creatine kinase
6 weeks of daily sprint training with longer rest intervals
no change of creatine kinase

38. Metabolic Adaptations to High Intensity Training (continued)
Glycolytic Energy System
↑ glyoclytic enzymes (10-25%)
Resistance training alone CAN NOT stimulate metabolic changes
Implications
“These studies suggest that athletes training for anaerobic sports need to include both resistance training and sprint or interval exercises in their conditioning programs in order to maximize their physiological adaptation for the sport” J. Hoffman

39. Metabolic Adaptations to High Intensity Training (continued)
Oxidative Energy System
High intensity training ↑ mitochondrial enzyme activity
When duration of exercises exceeds 3 minutes
Does not match gains from endurance training
Implications
An athlete who trains anaerobically may still generate some aerobic capacity improvements

40. Metabolic Adaptations to High Intensity Training (continued)
Improvements to buffering capactiy
Allows greater [ ] of lactic acid before effecting muscular output
↑ 12-50% from a 8 week high intensity training program
↑ 9.6% of blood lactate after 6 weeks of high intensity cycling program (Jacobs et al., 1987)