Metabolic System and Exercise. EXS 558 Lecture #4 September 21, 2005. 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.
September 21, 2005
1.) exercise (physical stress)
2.) psychological stress
3.) fluid volume stress
a.) no response, endurance activity has no effect
b.) ↑ circulating testosterone levels
c.) ↓ circulating testosterone levels
d.) first it increases and then decreases
1.) By Subject: Exercise Science & Sport Studies
c.) Physical Education Index
2.) Fulltext Database (.PDF available online)
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.
ATP + water ADP + Pi + 7,000 cals/mol
- energy stored in ATP will sustain life for about 90 seconds
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
*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.
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
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
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.
wCarbohydrate oxidation involves glycolysis, the Krebs cycle, and the electron transport chain to produce up to 39 ATP per molecule of glycogen aerobically.
wThe 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.
wThe oxidative system uses oxygen and produces more energy than the anaerobic systems.
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.
“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