Energy for Muscular Activity

Sport Books Publisher 1

Energy for Muscular Activity

Chapter 7


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


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


ATP Cycle Overview

a) ATP breakdown

b) Phosphorylation

c) ATP resynthesis


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)


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


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


The Energy Systems

a) High energy phosphate system

b) Anaerobic glycolytic system

c) Aerobic oxidative system


The Roles of the Three Energy The Roles of the Three Energy Systems in Competitive SportSystems in Competitive Sport



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)


High Energy Phosphate System

CreatineCreatinePP ENERGYENERGY

ADP + Pi ATPADP + Pi ATP


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


The Anaerobic Glycolytic System Overview



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


The Anaerobic Glycolytic System


ENERGYENERGY

Lactic AcidLactic Acid

GlycogenGlycogen


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


The highly complex metabolic pathways of glycolysis

)


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


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


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


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


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




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


Aerobic Oxidative System


ENERGYENERGY

Carbon DioxideCarbon Dioxide WaterWater

GlycogenGlycogenO2O2

ProteinProtein

FatFat


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


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


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


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


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


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


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


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


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


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.

Energy for Muscular Activity

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