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Sport Books Publisher 1
Energy for Muscular Activity
Chapter 7
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Learning Objectives:
To develop an awareness of the basic chemical processes the body uses to produce energy in the muscles
To develop an understanding of the body’s three main energy systems
To introduce the effect of training and exercise on the energy systems
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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
ATPMuscular Work
Digesting Food
Thermoregulation
Breakdown of Energy currency Biochemical processes
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ATP Cycle Overview
a) ATP breakdown
b) Phosphorylation
c) ATP resynthesis
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1. Hydrolysis of the unstable phosphate groups ofATP molecule by H2O
3. Energy is released (38 to 42 kJ, or 9 to 10 kcal/mol ATP)
ATP H2O++ Energy++ Pi++
2. Phosphate molecule (Pi) is released from ATP (ATP ADP)
ADP
a) ATP breakdown (ATP turnover)
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1. Energy released by ATP turnover can be used by body when a free Pi group is transferred to another molecule(phosphorylation)
Energy for muscle contractionMolecule Pi++
b) Phosphorylation
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1. 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 Pi
ATPADP Energy++ Pi++
3. Regeneration of ATP requires energy (from breakdown of food molecules)
c) ATP resynthesis
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The Energy Systems
a) High energy phosphate system
b) Anaerobic glycolytic system
c) Aerobic oxidative system
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The Roles of the Three Energy The Roles of the Three Energy Systems in Competitive SportSystems in Competitive Sport
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High Energy Phosphate System Overview
Primary energy source:
Duration of activity:
Sporting events:
Advantages:
Limiting factors:
Stored ATP, CP
7 to 12 s
Weightlifting, high jump, long jump, 100 m run, 25 m swim
Produces very large amount of energy in a short amount of timeInitial concentration of high energy phosphates (ATP, PC)
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High Energy Phosphate System
CreatineCreatinePP ENERGYENERGY
ADP + Pi ATPADP + Pi ATP
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Training the High Energy Phosphate System
a) Interval training:
- 20 percent increase in CP (creatine phosphate) stores- no change in ATP stores- increase in ATPase function (ATP ADP + Pi)- 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 percent
- 100 percent increase in resting ATP stores
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The Anaerobic Glycolytic System Overview
Primary energy source:
Duration of activity:
Sporting events:
Advantages:
Limiting factors:
Stored glycogen, blood glucose
12 s to 3 min
Lactic acid build up, H+ ions build up (decrease of pH)
800 m run, 200 m swim, downhill ski racing, 1500 m speedskating
Ability to produce energy under conditions of inadequate oxygen
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The Anaerobic Glycolytic System
ADP + Pi ATPADP + Pi ATP
ENERGYENERGY
Lactic AcidLactic Acid
GlycogenGlycogen
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GlycolysisA 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
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The highly complex metabolic pathways of glycolysis
)
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Anaerobic ThresholdThe exercise intensity at which lactic acid begins to accumulate within the bloodThe point during exercise where a person begins to feel discomfort and burning sensations in the muscles Lactic acid is used to store pyruvate and hydrogen ions until they can be processed by the aerobic system
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The Anaerobic Glycolytic System
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
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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
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Glucose stored in blood
Glycogen stored in muscle or liver
Complex Carbohydrates
Digestive system
Glycogen
Glucogenesis
Circulation of glucose throughout body
Glucose
Blood Stream
Carbohydrate breakdown and storage
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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 non-working muscles
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Primary energy source:
Duration of activity:
Sporting events:
Advantages:
Limiting factors:
Glycogen, glucose, fats, proteins
> 3 min
Lung function, max blood flow, oxygen availability, excessive energy demands
Walking, jogging, swimming, walking up stairs
Large output of energy over a long period of time, removal of lactic acid
The Aerobic Oxidative System Overview
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Aerobic Oxidative System
ADP + Pi ATPADP + Pi ATP
ENERGYENERGY
Carbon DioxideCarbon Dioxide WaterWater
GlycogenGlycogenO2O2
ProteinProtein
FatFat
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The Aerobic Oxidative System
The most important energy system in the human bodyBlood lactate levels remain relatively low (3 to 6 mmol/L blood)Primary source of energy (70 to 95 percent) 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 mitochondriac) 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
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The Oxidative Phosphorylation System
Two Pathways: Kreb’s Cycle and Electron Transport Chain
Biochemical process used to resynthesize ATP by combining ADP and Pi 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
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Cori CycleLactic acid is taken to the liver to be metabolized back into pyruvic acid and then glucose
GlucoseGlucose
GlycogenGlycogenLactateLactate
GlucoseGlucose
GlycogenGlycogenLactateLactate
Blood Glucose
Blood Lactate
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Evaluated by measuring the maximal volume of oxygen that can be consumed per kilogram of mass in a given amount of timeThis 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 bloodb) 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-v O2 difference)- Depends upon the rate of O2 diffusion from capillaries and
the rate of O2 utilization
The Power Of The Aerobic System
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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,
insulate the body from cold, and serve to transport vitamins
– each gram of fat contains 9 kilocalories of energy
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Effects 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 muscle fibers- increases the activity of enzymes (Kreb’s cycle)- preferential use of fats over glycogen during exercise
Endurance training increases the max aerobic power of a sedentary individual by 15 to 25 percent regardless of age
An older individual adapts more slowly
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Summary of the three energy systemsCharacteristic High energy phosphate Anaerobic glycolytic Aerobic oxidative
Other names phosphagen, ATP/CP lactic acid steady stateFuel source(s) stored ATP, PC stored glycogen, blood
glucoseglycogen, glucose, fats,
proteinsEnzyme sytem used in breakdown
single enzyme single enzyme multiple enzymes
Muscle fibre type(s) recruited SO, FOG, FG SO, FOG, FG depends on level of effortPower output requirement high high lowMetbolic byproducts ADP, P, C lactic acid CO2, H2Omaximum rate of ATP production (mmol/min)
3.6 1.6 1
Time to maximal ATP production
1 sec 5-10 sec 2-3 min
Maintenance time of maximal ATP production
6-10 sec 20-30 sec 3 min
Time to exhaustion of system 10 sec 3040 sec 5-6 minATP production capacity (mol) 0.6 1.2 theoretically unlimited
Relative % ATP contribution to efforts of 10 sec
50 35 15
Relative % ATP contribution to efforts of 30 sec
15 65 20
Relative % ATP contribution to efforts of 2 min
4 46 50
Relative % ATP contribution to efforts of 10 min
1 9 90
Time for total recovery (sec) 3 min 1-2 hr 30-60 minTime for one half recovery (sec)
20-30 sec 15-20 min 5-10 min
Ultimate limiting factor(s) Depletion of ATP / creatine phosphate stores
Lactic acid accumulation resulting from production
exceeding buffer capacity.
Depletion of carbohydrate stores, insufficient oxygen,
heat accumulation
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The Role of Three Energy Systems During an All-out Exercise Activity of Different Duration
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Factors Affecting Physical Performance
Somatic Factors Nature of the Work Psychic Factors Environmental FactorsSex Intensity Attitude DietAge Duration Motivation Temperature
Body distribution Technique (efficiency) Air pressure (hypobaric and hyperbaric)State of health Body position Air pollution
Drugs Mode NoiseStrength Type
Fibre type distibution Work:rest schedule
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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.