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chapter

1

Introduction to Nutrition for Exercise and Health

Physiology of Aerobic & Anaerobic Exercise

Prof Jennifer Broxterman, RD, MScFN3373: Nutrition for Physical ActivityLecture 2

What Fuels Physical Activity?

ATP

Hydrolysis of ATP

ATP & Energy Use by Exercising Muscles

Rephosphorylation of ADP to Form ATP

Energy Systems that Replenish ATP

Creatine Phosphate

Anaerobic Glycolysis

Oxidative Phosphorylation

ATP

Characteristics of the 3 Energy Systems

Speed of Action

Amount of ATP

Replenished

Duration of Action

Creatine Phosphate

Very Fast Very Small Very Short

Anaerobic Glycolysis

Fast Small Short

Oxidative Phosphorylation

Very Slow Large Very Long

Energy System 1

Creatine Phosphate

Creatine Phosphate Energy System

The CrP Energy System Rephosphorylates ADP to ATP Rapidly

• Anaerobic reaction• If [ATP] in a muscle ↓ there is an accompanying

↑ in ADP in the cell – ↑ in the activity of CK, allowing the reaction to

proceed faster

• CrP is stored in very small amounts• At very high-intensity exercise it takes ~ 5-10

seconds for CrP in the muscle to be depleted and fatigue to set in

Characteristics of the CrP Energy System

• One chemical step• Catalyzed by creatine kinase (CK)• Very fast reaction• One ATP per CrP molecule• 5-10 second duration• Anaerobic• Fatigue associated with CrP depletion• Predominant energy system in very high-

intensity exercises (power events)

Creatine Phosphate & ADP Rephosphorylation

The Creatine Shuttle

Energy System 2

Anaerobic Glycolysis

Glucose

GLYCOLYSIS

2 Pyruvic Acid molecules

If Oxygen is AbsentIf Oxygen is Present

Anaerobic Metabolism

Aerobic Metabolism

Lactic AcidCO2 + H2O

2 ATP

36-38 ATP

The Anaerobic Glycolysis Energy System

Anaerobic Glycolysis

Cori Cycle

Energy System 3

Oxidative Phosphorylation

Glucose

GLYCOLYSIS

2 Pyruvic Acid molecules

If Oxygen is AbsentIf Oxygen is Present

Anaerobic Metabolism

Aerobic Metabolism

Lactic AcidCO2 + H2O

2 ATP

36-38 ATP

Cellular Respiration Overview

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

(glucose) (heat and ATP)

• The energy in one molecule of glucose yields 36 ATP

• Aerobic respiration involves a series of 3 reactions:– Glycolysis– Krebs Cycle– Electron Transport Chain

Glycolysis

Oxidative Phosphorylation Energy System

Glycolysis, Krebs Cycle, Electron Transport Chain of Oxidative Phosphorylation

Macronutrients as Fuel Sources during Exercise

Beta Oxidation

Respiratory Exchange Ratio

Respiratory Exchange Ratio

Respiratory Exchange Ratio

RER Chart