Energy Metabolism and Metabolic Adaptations to Training Chapter 3

Learning Objectives Understand why physical educators, coaches, and exercise scientists need a basic understanding of energy metabolism. Have a basic knowledge of aerobic and anaerobic metabolism. Be able to differentiate between activities that are primarily aerobic or anaerobic. Be able to identify the metabolic adaptations to endurance, sprint, and resistance training.

Defining Energy Metabolism Using the food we eat to store energy in the form of adenosine triphosphate (ATP), which we break down, thus releasing energy and using it to cause muscles to contract. Involves the processes of anabolism and catabolism:  Anabolism: Structures are created.  Catabolism: Structures are broken down.

Why Do We Need to Understand Energy Metabolism? ATP is the only source of energy used directly for muscle contraction. Producing enough ATP is essential to being physically active. Many important adaptations to exercise training involve aspects of energy metabolism. The metabolic demands of an activity are important when designing training/exercise programs.

Aerobic vs. Anaerobic Metabolism Aerobic metabolism:  The production of ATP with oxygen Anaerobic metabolism:  The production of ATP without oxygen

Approximate Percentages of Aerobic and Anaerobic Contributions to ATP Production Activity% Aerobic% Anerobic Resistance training 0100 Circuit weight lifting meter run0100 3,000-meter run ,000-meter run98 2 Marathon meter swim20 80 Football5 95 Tennis25 75 Speed skating15 85 Boxing50 50

Your Perspective Is knowing the importance of aerobic vs. anaerobic ATP production important to you, as you exercise and play sports? What if you were designing a training program and organizing practice times for:  A young tennis player  Someone training for a boxing match

Fat, Carbohydrate, and Protein Can Produce ATP Aerobically

Three Characteristics of Enzymes 1. Speed up or catalyze a reaction. They convert reactants at the rate necessary to meet the demands of an activity. 2. Are not changed when they catalyze a reaction. 3. Do not change the result of the reaction.

Your Perspective What do you think of automobile racing as a sport? Do you believe that racecar drivers are real athletes? After reading about Jacobs and Olvey’s (2000) study of automobile racing, does this change your opinions regarding racecar drivers?

Lock-and-Key Method of Enzymes Enzymes must fit precisely with reactants to catalyze a reaction. Active site (on the enzyme) Binding site (on the reactant)

Turnover Rate of Enzymes Efficiency and effectiveness with which an enzyme can convert a reactant into a product Rate-limiting enzyme:  The one specific enzyme in a metabolic pathway with the lowest turnover rate; the weak link in the chain.

Factors That Determine Turnover Rate Temperature and acidity (pH) of the cellular environment Concentration and activity of reactants and enzymes End product inhibition, or allosteric inhibition Availability and concentrations of cofactors and coenzymes

Anaerobic ATP Production Two pathways: 1. ATP-PC system 2. Anaerobic glycolysis

Enzymatic Reactions in the ATP–PC System

Diagram of Anaerobic Glycolysis See the full-sized figure on the AESP Resource Site.AESP Resource Site

Aerobic Metabolism The Krebs Cycle See the full-sized figure on the AESP Resource Site.AESP Resource Site

Aerobic Metabolism Electron Transport System

Anaerobic Breakdown of Glucose vs. Aerobic Metabolism

Fat and Protein Metabolism ATP production from fatty acid sources is important in many forms of exercise. Protein metabolism can also provide energy.  Less than 15–18 percent of total ATP production during exercise. Triglycerides Polypeptides

Power and Capacity of Energy Production Systems Power: The amount of ATP a system can produce per unit of time  Most powerful: ATP-PC system  Least powerful: Fatty acid oxidation Capacity: The total amount of energy that can be produced  Lowest capacity: ATP-PC system; limited store of phosphagens  Greatest capacity: Fatty acid metabolism; inexhaustible supply of energy

Inverse Relationship Between Power and Capacity

Metabolic Adaptations to Training Adaptations are specific to the type of training. 1. Endurance training (aerobic metabolism) 2. Sprint training (anaerobic metabolism) 3. Resistance training

Adaptations from Endurance Training In the skeletal muscle and cardiovascular system: Myoglobin Mitochondrial size, number, and enzymes Glucose-alanine-glucose cycle Glycolytic enzymes Use of free fatty acids for ATP production

Adaptations from Sprint Training Increases in cellular concentrations of key anaerobic enzymes:  Can improve sprinting performance. Increase in phosphocreatine stores in muscle:  Can maintain high-intensity exercise for a longer period of time before depletion and fatigue.

Adaptations from Resistance Training Increases in:  Strength/size of exercised muscle  Force production capabilities Metabolic effects are specific to the type of program.

Where to Learn More Review of anaerobic metabolism:  Glycolysis and Krebs cycle:  htm htm Electron transport system:  Basic physiology and cell energy metabolism: 

ACSM Guideline— Ability to distinguish between aerobic and anaerobic metabolism.  What kind of training program would you design for a long-distance runner? For a sprinter?  Would you design similar programs for swimmers who swim short distances and for those who swim long distances?