Energetics of muscle contraction

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Energetics of muscle Energetics of muscle contractioncontraction

Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood

Objectives Objectives Specific Objectives: Goal/Aim (Main Objective):

To explain the sources of energy for muscle contractionAt the end of this lecture students will be able to

Explain Explain Work Output Work Output During Muscle ContractionDuring Muscle ContractionList List Sources of Energy Sources of Energy for Muscle Contractionfor Muscle ContractionName Name Muscle Metabolic Systems Muscle Metabolic Systems in Exercisein ExerciseCompare different Energy Systems Compare different Energy Systems of muscle of muscle Give examples of What Types of Sports Use Which What Types of Sports Use Which Energy Systems? Energy Systems? Explain the principles of Effect of diet Effect of diet on the rate of on the rate of muscle glycogen replenishment after prolonged exercise muscle glycogen replenishment after prolonged exercise Describe Describe EfficiencyEfficiency of Muscle Contraction of Muscle Contraction

22Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood

Lesson Contents Lesson Contents Work Output Work Output During Muscle ContractionDuring Muscle ContractionSources of Energy Sources of Energy for Muscle Contractionfor Muscle ContractionMuscle Muscle Metabolic Systems Metabolic Systems in Exercisein ExerciseComparisonComparison of Energy Systems of Energy SystemsWhat Types of What Types of SportsSports Use Which Energy Use Which Energy Systems? Systems? Effect of Effect of dietdiet on the rate of muscle glycogen on the rate of muscle glycogen replenishment after prolonged exercise replenishment after prolonged exercise EfficiencyEfficiency of Muscle Contraction of Muscle Contraction


World’s biggest biceps World’s biggest biceps (1/5)(1/5)

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MCQ 1MCQ 1For very high force contractions lasting 1-2 seconds, the initial energy source is from:

a) Glycolysisb) Creatine phosphorylationc) Phosphocreatine storesd) ATP storese) Gluconeogenesis


MCQ 2MCQ 2The most rapid method to The most rapid method to resynthesize ATP during exercise is resynthesize ATP during exercise is through:through:

a) Glycolysisa) Glycolysisb) Phosphocreatine breakdownb) Phosphocreatine breakdownc) Tricarboxylic acid cycle (Krebs’ cycle)c) Tricarboxylic acid cycle (Krebs’ cycle)d) Glycogenolysisd) Glycogenolysise) Gluconeogenesise) Gluconeogenesis


MCQ 3MCQ 3If a person runs a 10-kilometer race, what If a person runs a 10-kilometer race, what is the source of most of the adenosine is the source of most of the adenosine triphosphate (ATP) produced?triphosphate (ATP) produced?

a.a. Glycogen –lactic acid systemGlycogen –lactic acid systemb.b. Metabolism of glucose, fat, and amino Metabolism of glucose, fat, and amino

acid acid c.c. Phosphagen systemPhosphagen systemd.d. Phosphocreatine systemPhosphocreatine systeme.e. Stored ATPStored ATP


Characteristics of muscle Characteristics of muscle contraction/ Properties of contraction/ Properties of

musclemuscle1.1. EnergeticsEnergetics of Muscle Contraction of Muscle Contraction 2.2. Effect of Amount of Actin and Myosin Effect of Amount of Actin and Myosin

Filament Filament OverlapOverlap on Tension on Tension Developed by the Contracting Muscle Developed by the Contracting Muscle

3.3. Relation of Relation of VelocityVelocity of Contraction to of Contraction to LoadLoad

4.4. Characteristics of Characteristics of WholeWhole Muscle Muscle ContractionContraction

I.I. Isometric Versus Isotonic ContractionIsometric Versus Isotonic Contraction II.II. Fast Versus Slow Muscle FibersFast Versus Slow Muscle Fibers


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Energetics of Muscle Energetics of Muscle Contraction Contraction

I.I. Work Output During Muscle Work Output During Muscle Contraction Contraction

II.II. Sources of Energy for Muscle Sources of Energy for Muscle Contraction Contraction

III.III. Efficiency of Muscle Contraction Efficiency of Muscle Contraction


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I. Work Output During I. Work Output During Muscle Contraction Muscle Contraction

When a muscle contracts against a load, it When a muscle contracts against a load, it performs performs workwork.. EnergyEnergy is transferred from is transferred from the muscle to the external load the muscle to the external load WorkWork= W= L = W= L xx D D L = L = loadload, D = , D = distancedistance of movement of movement against the load. against the load. The The energyenergy requiredrequired to perform the work to perform the work is is derivedderived from the from the chemicalchemical reactionsreactions in in the muscle cells during contractionthe muscle cells during contraction


Assessment Q.1 Assessment Q.1 Where Energy is transferred from Where Energy is transferred from the muscle?the muscle?


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II. II. Sources of Energy for Sources of Energy for Muscle Contraction Muscle Contraction

ATP:ATP: MostMost of this energy for walk-along of this energy for walk-along mechanism mechanism smallsmall amountsamounts for for

(1) pumping (1) pumping calciumcalcium ions from the ions from the sarcoplasm into the sarcoplasmic reticulum sarcoplasm into the sarcoplasmic reticulum (2) pumping (2) pumping sodiumsodium and and potassiumpotassium

(action potentials)(action potentials) concentration of ATP sufficient for concentration of ATP sufficient for only only 1 to 2 seconds1 to 2 seconds rephosphorylatedrephosphorylated within another within another fraction of a second for continuous fraction of a second for continuous contraction contraction Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood

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several sources of the several sources of the energy for energy for

rephosphorylation rephosphorylation 1.1.phosphocreatinephosphocreatine2.2.glycolysis of glycolysis of glycogenglycogen3.3.oxidativeoxidative metabolismmetabolism


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rephosphorylation rephosphorylation 1.1.phosphocreatinephosphocreatine ATP + ATP + phosphocreatine=phosphocreatine= 5 to 8 5 to 8

seconds seconds


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rephosphorylation rephosphorylation 2. glycolysis of 2. glycolysis of glycogenglycogenpreviously stored previously stored Rapid Rapid Converted to Converted to pyruvicpyruvic acidacid and and lactic acid; this ; this conversion liberates energy that is used to convert ADP conversion liberates energy that is used to convert ADP to ATP to ATP importanceimportance 1.1. absenceabsence ofof oxygenoxygen (many seconds to more than a (many seconds to more than a

minute)minute)2.2. rapid rapid DisadvantageDisadvantage: :

end products ( about end products ( about 11 minuteminute ) )


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rephosphorylation rephosphorylation 3. oxidative3. oxidative metabolismmetabolism (combining (combining oxygen with the end products of glycolysis and oxygen with the end products of glycolysis and with various other cellular with various other cellular foodstuffsfoodstuffs ) )

1.1. More than More than 9595 perper centcent 2.2. carbohydrates, fats, and protein (greatest carbohydrates, fats, and protein (greatest

proportion of energy comes from fats , but for 2-4 proportion of energy comes from fats , but for 2-4 hours)hours)

3.3.manymany hourshours


Muscle Metabolic Systems in Muscle Metabolic Systems in ExerciseExercise

(1)(1) the phosphocreatine-creatine the phosphocreatine-creatine systemsystem, ,

(2)(2) the glycogen-lactic acid system,the glycogen-lactic acid system, and and

(3)(3) the aerobic systemthe aerobic system. . Adenosine Triphosphate (ATP)


Assessment Q.2Assessment Q.2Name the Muscle Metabolic Name the Muscle Metabolic Systems in ExerciseSystems in Exercise


Muscle Metabolic Systems in Muscle Metabolic Systems in ExerciseExercise


Comparison of Energy Comparison of Energy SystemsSystems

Energy System Moles of ATP/min

Time

Phosphagen system

4 8 to 10 seconds

Glycogen-lactic acid system

2.5 1.3 to 1.6 minutes

Aerobic system 1 Unlimited time (as long as nutrients last)


What Types of Sports Use What Types of Sports Use Which Energy Systems? Which Energy Systems? Phosphagen system, almost entirelyPhosphagen system, almost entirely

100-meter dash 100-meter dash Jumping Jumping

Phosphagen and glycogen-lactic acid Phosphagen and glycogen-lactic acid systemssystems

200-meter dash 200-meter dash Glycogen-lactic acid system, mainlyGlycogen-lactic acid system, mainly

400-meter dash 400-meter dash 100-meter swim 100-meter swim

Glycogen-lactic acid and aerobic systemsGlycogen-lactic acid and aerobic systems 800-meter dash 800-meter dash 200-meter swim 200-meter swim

Aerobic systemAerobic system 10,000-meter skating 10,000-meter skating Marathon run (26.2 miles, 42.2 km) Marathon run (26.2 miles, 42.2 km) Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood 2626

Assessment Q.3Assessment Q.3What Types of Energy System is What Types of Energy System is used for Marathon run ? used for Marathon run ?


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Energetics of Muscle Energetics of Muscle Contraction Contraction

Work Output During Muscle Work Output During Muscle Contraction Contraction

Sources of Energy for Muscle Sources of Energy for Muscle Contraction Contraction

III. Efficiency of Muscle Contraction III. Efficiency of Muscle Contraction


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III. Efficiency of Muscle III. Efficiency of Muscle Contraction Contraction

The The efficiencyefficiency of an engine of an engine percentage of percentage of energyenergy inputinput that is that is converted into converted into workwork insteadinstead ofof heatheat

less than less than 2525 perper centcent , , remainderremainder becoming becoming heatheat ReasonReason

one half of the energy in foodstuffs is one half of the energy in foodstuffs is lost during the lost during the formationformation ofof ATPATP only 40 to only 40 to 4545 perper centcent of the of the energy in the ATP itself energy in the ATP itself cancan bebe convertedconverted into work. into work.


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III. Efficiency of Muscle III. Efficiency of Muscle Contraction Contraction

MaximumMaximum efficiencyefficiency contracts at a moderate contracts at a moderate velocityvelocity

slowlyslowly or without any movement or without any movement maintenancemaintenance heatheat

tootoo rapidrapid to overcome to overcome viscousviscous frictionfriction within within the musclethe muscle

maximum efficiency is developed maximum efficiency is developed when the velocity of contraction is when the velocity of contraction is about about 3030 perper centcent of maximum. of maximum.


Essential Points to Essential Points to Remember Remember When a muscle contracts against a load, it

performs work, which is directly proportional to load and distance. Most of energy is used for walk-along mechanism; however, small amounts are utilized for pumping calcium, sodium and potassium. ATP already stored is sufficient for only 1 to 2 seconds; it is the rephosphorylatedSources of rephosphorylation include phosphocreatine, anaerobic metabolism, and oxidative metabolism.


Phosphocreatine, and ATP are sufficient for only 5 to 8 seconds.Glycolysis of previously stored glycogen can supply ATP for about 1 minute, through anaerobic metabolism.Oxidative metabolism provides more than 95 per cent energy for longer muscular activity upto many hours.Efficiency of Muscle Contraction is generally less than 25 per cent, remainder becoming heat.Maximum efficiency of muscle is when contracts at a moderate velocity, i.e. about 30 per cent of the maximum velocity.


MCQ 1MCQ 1For very high force contractions lasting 1-2 seconds, the initial energy source is from:

a) Glycolysisb) Creatine phosphorylationc) Phosphocreatine storesd) ATP storese) Gluconeogenesis


MCQ 2MCQ 2The most rapid method to The most rapid method to resynthesize ATP during exercise is resynthesize ATP during exercise is through:through:

a) Glycolysisa) Glycolysisb) Phosphocreatine breakdownb) Phosphocreatine breakdownc) Tricarboxylic acid cycle (Krebs’ cycle)c) Tricarboxylic acid cycle (Krebs’ cycle)d) Glycogenolysisd) Glycogenolysise) Gluconeogenesise) Gluconeogenesis


MCQ 3MCQ 3If a person runs a 10-kilometer race, what If a person runs a 10-kilometer race, what is the source of most of the adenosine is the source of most of the adenosine triphosphate (ATP) produced?triphosphate (ATP) produced?

a.a. Glycogen –lactic acid systemGlycogen –lactic acid systemb.b. Metabolism of glucose, fat, and amino Metabolism of glucose, fat, and amino

acid acid c.c. Phosphagen systemPhosphagen systemd.d. Phosphocreatine systemPhosphocreatine systeme.e. Stored ATPStored ATP


Assessment Q.4Assessment Q.4Write the complete name, & Write the complete name, & edition of physiology book you edition of physiology book you read. read.


Learning ResourcesLearning ResourcesGuyton and Hall (Text book of physiology), 13th Guyton and Hall (Text book of physiology), 13th EditionEditionGanong (Text book of physiology), 24th EditionGanong (Text book of physiology), 24th EditionHuman Physiology : from cells to system Human Physiology : from cells to system Lauralee Sherwood,9Lauralee Sherwood,9thth Edition Edition Human Physiology Stuart Ira Fox, 13th EditionHuman Physiology Stuart Ira Fox, 13th EditionRobert M. Berne, Matthew N. Levy. Physiology, Robert M. Berne, Matthew N. Levy. Physiology, 66thth edition editionInternetInternet

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ANY QUESTIONS?Prof. Dr. Rashid MahmoodProf. Dr. Rashid Mahmood4141

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Energetics of muscle contraction

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