Exercise Science Section 5: Energy Systems and Muscle Fiber Types An Introduction to Health and Physical Education Ted Temertzoglou Paul Challen ISBN 1-55077-132-9

The Three Energy Nutrients Carbohydrates Proteins Fats © iStockphoto.com/”Roman Chmiel” © iStockphoto.com/”og-vision/OlgaLIS” © iStockphoto.com/”Kativ”

The Role of Carbohydrates Carbohydrates are the most abundant organic substances in nature, and they are essential for human and animal life. © iStockphoto.com/”YinYang”

Adenosine Triphosphate (ATP) Made in the mitochondrion Resynthesized in two ways Aerobically Anaerobically ATP ADP + P + ENERGY

Two Energy Systems Anaerobic System Without the use of oxygen (O2) None of its metabolic activity will involve O2 Utilizes chemicals and enzymes; occurs in the muscle fibre Short-lived Aerobic System In the presence of oxygen (O2) All of its metabolic activity will involve O2 Occurs in the mitochondria Leads to the complete breakdown of glucose

Three Metabolic Pathways ATP-PC System (anaerobic alactic) Glycolysis (anaerobic lactic) Cellular respiration (aerobic)

ATP-PC System ATP-PC System (anaerobic alactic) First of two anaerobic energy pathways Relies on the action of stored ATP and phosphocreatine Yields enough ATP for 10–5 seconds of energy Provides highest rate of ATP synthesis No by-product PC + ADP ATP + CREATINE

Glycolysis Glycolysis (anaerobic lactic) Second anaerobic energy pathway Provides additional 1–3 minutes in high-level performance Involves 11 separate biochemical reactions Uses glucose and glycogen to make ATP Yields twice as much ATP By product is lactic acid (LA) C6H12O6 + 2ADP = 2Pi 2C3H6O3 + 2ATP + 2H2O (Glucose) (Lactate)

The Aerobic System Aerobic system (cellular respiration) Third energy system Glycolysis Krebs cycle Electron transport chain Uses glucose, glycogen, fats, and protein to make ATP Lasts 120 seconds and beyond C6H12O6 + 6O2 + 36ADP + 36Pi 6CO2 + 36ATP + 6H2O

Energy Pathways

Energy Sources for Different Sports

Lactic Acid

Energy from Fats and Protein Aerobic system (cellular respiration) Third energy system Glycolysis Krebs cycle Electron transport chain Uses glucose, glycogen, fats, and protein to make ATP Lasts 120 seconds and beyond © iStockphoto.com/”Morgan Lane Photography”

Slow-Twitch and Fast-Twitch Muscles Slow-twitch muscle fibres: Most active during: long-distance running, swimming, and cycling Red or dark in colour Generate and relax tension slowly; able to maintain a lower level of tension for long durations Low levels of myosin ATPase and glycolytic enzymes High levels of oxidative enzymes Fast-twitch muscle fibres: Ideal for: short sprints, powerlifting, and explosive jumping Pale in colour Ability to tense and relax quickly; generate large amounts of tension with low endurance levels High levels of myosin ATPase and glycolytic enzymes

Approximate Distribution of Muscle Fibre Types for Different Sports

Three Fibre Types Type I or Slow-Oxidative (SO) Generate energy slowly Fatigue-resistant Depend on aerobic processes Type IIA or Fast-Oxidative Glycolytic (FOG) Intermediate-type muscle fibres Allow for high-speed energy release Allow for glycolytic capacity Type IIB of Fast-Glycolytic (FG) Store glycogen and high levels of enzymes Allow for quick contraction without the need for oxygen

Characteristics of Different Muscle Fibre Types