1. Energy Systems and Muscle Fibre Types
SECTION 5
Energy Systems and Muscle Fibre Types

2. Energy is defined as the ability to do work.
Work is defined as the application of force through a distance.
Six forms of energy:
1. light 4. nuclear
2. heat 5. chemical
3. electrical 6. mechanical
Muscles convert CHEMICAL energy into MECHANICAL energy

3. The Chemistry of Energy Production
Energy in the human body is derived from the breakdown of complex nutrients like carbohydrates, fats, and proteins.
The end result of this breakdown is production of the adenosine triphosphate (ATP) molecule.
ATP provides energy necessary for body functions
Carbohydrates
Fats
Proteins
ATP
Muscular Work
Digesting Food
Thermoregulation
Breakdown of
Energy currency
Biochemical processes

4. ANABOLIC – reactions that require energy to synthesize moleucles
The Three Energy Nutrients
Carbohydrates – glucose, glycogen
Proteins – amino acids
Fats – fatty acids
Metabolism refers to the process by which energy is supplied throughout the body. The chemical reactions will either require energy or release energy, the body’s metabolism may be thought of as a balancing act.
ANABOLIC – reactions that require energy to synthesize moleucles
CATABOLIC – reactions that release energy as they involve the breakdown of molecules

5. Adenosinetriphosphate (ATP)
ATP – is made in the mitochondrion
ATP is only an immediate source of energy for muscle contraction
Muscles have a small supply of ATP which satisfies the body’s initial needs, but is used quickly. Therefore, ATP must be re-synthesized.
ATP – is re-synthesized in two ways: aerobically and anaerobically

6. Aerobic and Anaerobic Aerobic – means in the presence of oxygen (02)
– all of its metabolic activity will involve 02
Anaerobic
– means without the use of oxygen (02)
– none of its metabolic activity will involve 02

7. ATP Cycle Overview a) ATP breakdown b) Phosphorylation
c) ATP resynthesis

8. a) ATP breakdown (ATP turnover)
ADP
H2O +
Energy + P +
1. Hydrolysis of the unstable phosphate groups of
ATP molecule by H2O
2. Phosphate molecule (P) is released from ATP
(ATP ADP)
3. Energy is released (38-42 kJ, or 9-10kcal/ mol ATP)

9. b) Phosphorylation
Molecule P +
Energy for muscle contraction
1. Energy released by ATP turnover can be used by body
when a free P group is transferred to another molecule
(phosphorylation)

10. c) ATP resynthesis ATP ADP Energy + P +
Initial stores of ATP in the muscles are used up
very quickly and ATP must be regenerated
2. ATP is formed by recombination of ADP and P
3. Regeneration of ATP requires energy (from
breakdown of food molecules)

11. THREE ENERGY SYSTEMS FOR MUSCLES
AEROBIC - burn sugar (glucose/glycogen) and fat, with oxygen
ANAEROBIC - burn sugar without oxygen and get small energy AND LACTIC ACID
CREATINE PHOSPHATE - allows muscle to replenish ATP quickly but not for long, continual durations

12. The Energy Systems c) the aerobic system: cellular respiration
the high energy phosphagen system
(anaerobic)  ATP-PC System (anaerobic alactic)
the anaerobic glycolysis system
 Glycolysis (anaerobic lactic)
c) the aerobic system: cellular respiration

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

14. 1. The High Energy Phosphate System

15. High Energy Phosphate System Muscle fibers have a unique molecule called creatine phosphate that can transfer its high energy phosphate group to ADP thus forming ATP and creatine.
Creatine P
ENERGY
ADP + Pi  ATP

16. ATP-PC System
Creatine phosphate is a high energy molecule where the phosphate can be broken off easily and used to convert ADP to ATP
Anaerobic alactic (without oxygen, no production of lactic acid)
Uses stored ATP and creatine phosphate from within the muscle tissue. This supply is limited.
No by-products

17. 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

18. The High Energy ATP - PC System Overview Aka: Phosphagen System
Primary energy source:
Duration of activity:
Sporting events:
Advantages:
Limiting factors:
Stored ATP, PC (phosphate creatine)
7-12 s
Power events such as: weight lifting, high jump, long jump, 100m run, 25m swim
Produce very large amount of energy in a short amount of time (very quick)
Initial concentration of high energy phosphates (ATP, PC) stored in muscles is minimal

19. Training the High Energy Phosphate System
a) Interval training:
- 20% increase in CP (creatine phosphate) stores
- no change in ATP stores
- increase in ATPase function (ATP -> ADP+P)
- increase in CPK (creatine phosphokinase) function (CPK breaks down CP molecule and allows ATP resynthesis)
b) Sprint training:
- increase in CP stores up to 40%
- 100% increase in resting ATP stores

20. 2. The Anaerobic Glycolysis System

21. Glycolysis
A biochemical process that releases energy in the form of ATP from glycogen and glucose
anaerobic process (in the absence of oxygen)
The products of glycolysis (per molecule of glycogen):
- 2 molecules of ATP
- 2 molecules of pyruvic acid
The by-product of glycolysis (per molecule of glycogen):
- 2 molecules of lactic acid

22. 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 C3H6O3 + 2ATP + 2H2O (Glucose) (Lactate)

23. Anaerobic Threshold
The exercise intensity at which lactic acid begins to accumulate within the blood
The point during exercise where the person begins to feel discomfort and burning sensations in their muscles
Lactic acid is used to store pyruvate and hydrogen ions until they can be processed by the aerobic system

24. The Anaerobic Glycolytic System cont.
Starts when:
the reserves of high energy phosphate compounds fall to a low level
the rate of glycolysis is high and there is a buildup of pyruvic acid

25. Carbohydrate breakdown and storage
Complex
Carbohydrates
Digestive
system
Glucose
Blood
Stream
Glucose stored
in blood
Gluconeogenesis
Circulation of glucose
around body
Glycogen
Glycogen stored
in muscle or liver

26. Substrates for the anaerobic energy system
The primary source of substrates is carbohydrate
Carbohydrates:
primary dietary source of glucose
primary energy fuels for brain, muscles, heart, liver

27. Effect of Training on the Anaerobic Glycolytic System
Rate of lactic acid accumulation is increased in the trained individual
This rate can be decreased by:
a) reducing the rate of lactate production
- increase in the effectiveness of the aerobic oxidative system
b) increasing the rate of lactate elimination
- increased rate of lactic acid diffusion from active muscles
- increased muscle blood flow
- increased ability to metabolize lactate in the heart, liver and in non-working muscle

28. 3. The Aerobic Oxidative System

29. Aerobic Oxidative System
Glycogen O2
Protein
Fat
ADP + Pi  ATP
ENERGY
Carbon
Dioxide
Water

30. The Aerobic Oxidative System
The most important energy system in the human body
Blood lactate levels remain relatively low (3-6mmol/L bl)
Primary source of energy (70-95%) for exercise lasting longer than 10 minutes provided that:
a) working muscles have sufficient mitochondria to meet energy requirements
b) sufficient oxygen is supplied to the mitochondria
c) enzymes or intermediate products do not limit the Kreb’s cycle
Primary source of energy for the exercise that is performed at an intensity lower than that of the anaerobic oxidative system

31. The Oxidative Phosphorylation System
Two Pathways: Krebs Cycle & Electron Transport Chain
Biochemical process used to resynthesize ATP by combining ADP and P in the presence of oxygen
Takes place in mitochondrion (contains enzymes, co-enzymes)
Energy yield from 1 molecule of glucose is 36 ATP molecules
Energy yield from 1 molecule of fat up to 169 ATP molecules
By-products of this reaction: carbon dioxide, water

32. Aerobic System Only aerobic energy pathway
Lasts 120 seconds and beyond
Uses glucose, glycogen, fats, and proteins to make ATP
By-products are carbon dioxide (CO2) and water (H2O)

33. The Aerobic Oxidative System Overview
Primary energy source:
Duration of activity:
Sporting events:
Advantages:
Limiting factors:
Glycogen, glucose, fats, proteins
> 3 min
Lung function, max.blood flow, oxygen availability, excess. energy demands
Walking, jogging, swimming,
walking up stairs
Large output of energy over a long
period of time, removal of lactic acid

34. Cori Cycle
Lactic acid is taken to the liver to be metabolized back into pyruvic acid and then glucose
Glucose
Glycogen
Lactate
Blood Glucose
Blood Lactate

35. The Power Of The Aerobic System
Evaluated by measuring the maximal volume of oxygen that can be consumed per kilogram of mass in a given amount of time
This measure is called aerobic power or VO2 max (ml/min/kg)
Factors that contribute to a high aerobic power:
a) arterial oxygen content (CaO2)
- depends on adequate ventilation and the O2-carrying capacity of blood
b) cardiac output (Q = HR x stroke volume)
- increased by elevation of the work of heart and increased peripheral blood flow
c) tissue oxygen extraction (a-vO2 diff)
- depends upon the rate of O2 diffusion from capillaries and the rate of O2 utilization

36. The Substrates for the Aerobic System
Carbohydrates ( glycogen and glucose) and fats (triglycerides and fatty acids)
Fats:
found in dairy products, meats, table fats, nuts, and some vegetables
body’s largest store of energy, cushion the vital organs, protect the body from cold, and serve to transport vitamins
each gram of fat contains 9 calories of energy

37. Effect of Training on Aerobic Systems
Endurance training is the most effective method (long duration several times per week):
- increases vascularization within muscles
- increases number and size of mitochondria within the muscle fibres
- increases the activity of enzymes (Krebs cycle)
- preferential use of fats over glycogen during exercise
Endurance training increases the max aerobic power of a sedentary individual by 15-25% regardless of age
An older individual adapts more slowly

38. The Roles of the Three Energy Systems in Competitive Sport

39. The Role of Three Energy Systems During an All-out Exercise Activity of Different Duration

40. Discussion Questions:
1. What are the differences between the 3 energy systems?
2. List one advantage and one disadvantage of each of the 3 energy systems.
3. Give an example of three activities or sports that use each of (a) the high energy phosphate system, (b) the anaerobic glycolytic system, and (c) the aerobic oxidative system as their primary source of energy (one sport for each energy system).
4. What is the most important source of fuel in the body for all types of energy production - a substance also known as the energy currency of the body?
5. Define ATP turnover and ATP resynthesis.
6. Describe how each of the three energy systems could be trained most efficiently.