Physiology of ExerciseSaman Karunathiake

Exercise and EfficiencyWork - physiological stress Sports - ultimate limits Depends on: Capability - to utilise substrate for energy Conversion - Energy to Mechanical Energy Programming - of work to be done Working condition

During exercise Meet requirement of O2 & nutrients Remove CO2 & metabolites

Chemical, mechanical & thermal stimuli Alter the metabolic, cvs & resp. functions to meet the increase demand

Physiology of Exercise

Sports- Represents the highest levels of extreme stresses to which the body can be exposed.

Metabolism of the body during a marathon race can be increased to 2000% above normal.

Beyond the limits may be lethal.

100% increase of metabolism with extremely high fever approach the level of lethality.

What influences Athletic AbilityGeneticsTrainingTraining methodologyEnvironmentNutritionTrack/Arena surfacesShoesEtc

Physiology of ExerciseAdapted from J. Dempsey

Principles of physiological adaptationMuscles work against a loadToo hard, too fast too badSpecificity overload progressively for benefitF.I.T.T. ProgrammingF-frequency: number of time for weekI- intencity: works out as a% of maximum.T-Time:duration of exerciseT- Type of exercise

Effects of Athletic training on muscles

1. Inc. numbers of myofibrils and mitochondriae2. up to 120 % inc. in mitochondrial enzymes and electron transport carriers3. 60 80 % inc. in the components of the phosphogen metabolic system 4. 50 % inc. in stored glycogen. 5. 75 100 % inc. in stored triglyceride

Capabilities of both anaerobic and aerobic systems are enhanced. Maximum oxidation rate and efficiency of oxidative metabolic system increased by 45 %.

What muscle can do?Depends on - strength (size training/testos) - power ( work / unit time) - endurance (nutritive support)

StrengthPropotional to sizeMaximum contractile force=3-4 kg/cm2 muscle cross sectional areaWeight lifter- 150 cm2 quadriceps-525 kgHolding strength >40% = 735 kg

Depends on testesterone level, -Training

PowerTotal workload done in a given time (kg-m/min)

Determined by: -strength-Distance of contraction and -Number of time that it contract each minute

1st 8-10 secs7000Next 1 minutes4000Next half hour 1700

Critical Power

Energy, Work and PowerWork: when a Force (1 N) acts though a Distance of 1 meterMeasured in joulesWork = Force x DistanceForce (N) = mass x accelerationPower: Work/per unit of timeMeasured in j/s or Watts (W)

Work & PowerWorkForce x Distance50 kg x 1 m50 kgmPowerForce x Distance Time50 kg x 1 m 1 sec50 kgm/sec8.2 WattsExample: Moved 50 kg 1 m in 1 sec

EnduranceDepends on: -Nutritional supportMainly the glycogen stored in the muscle prior to exercise

Endurance enhance by high carbohydrate diet.

High carbohydrate diet40 g /kg muscleMixed diet20 g/kg muscleHigh fat diet6 g/kg muscle

High carbohydrate diet240 minutesMixed diet 120 minutesHigh fat diet85 minutes

Strength-Endurance ContinuumHigh Strength

High Power

Hypertrophy

Olympic liftingPower liftingThrowing Rowing Football100m Decathalon Swimming MarathonBasketballHigh Capillarity

High VO2max

Aerobic PowerHigh Mitochondria

BodybuildingRugby400mMile RunSoccer10K10 sec5 min> 2hrs

Concurrent Strength and Endurance TrainingHickson et al. 1980.

BioenergeticsPowered by chemical energy stored and generated.Use a combination of these depending on the intensity and duration of the exercise.

Phosphagen system a. ATPb.CP2. Glycogen lactic acid system3.Aerobic system

Energy Systems for Exercise

Energy SystemsMole of ATP/minTime to FatigueImmediate: Phosphagen (Phosphocreatine and ATP)45 to 10 secShort Term: Glycolysis(Glycogen-Lactic Acid)2.51.0 to 1.6 minLong Term: Aerobic1Unlimited time

ATP - Principle high energy molecule - 5 mmol/l in ICF - Stored ATP is sufficient only for 1 5 s of muscle contraction. - 1 ATP 7.3 kJ

Anaerobic vs Aerobic Energy SystemsAnaerobicATP-PCR : 10 sec.Glycolysis: < 3 minutesAerobicKrebs cycleElectron Transport Chain-Oxidation2 minutes +

100%% Capacity of Energy System10 sec30 sec2 min5 min +AerobicGlycolysisPhosphagen (ATP-PCR)Energy Transfer Systems and Exercise

The Phosphagen System

1. Phosphahgen system :- a) ATP present in muscles - basic source of energy for muscle contraction

7300 cals 7300 cals ATP --------------- ADP ----------------- AMP - PO3`` - PO3``

3 seconds of maximal muscle power ( 5-6 secs )

b) Release of energy from phosphocreatine (ATP/CP system- power for 8-10 sec) for 100 m dash

10300 cals Creatine~PO3`` ----------------- Creatine + PO``

up to 10 seconds of maximal muscle power ( next 10-15 secs)

This system provides energy for bursts of muscle power

THE CREATINE PHOSPHATE SYSTEMADENOSINE PHOSPHATE(ADP) + CREATINE PHOSPHATE = ATP (ENERGY) This system is extremely efficient It does not need oxygen It leaves no waste productsHOWEVER WE ARE ONLY ABLE TO USE THIS FOR ABOUT 10-15 SECONDS BEFORE THIS SYSTEM RUNS OUT.THINK 100 metres

Aerobic and Anaerobic ATP ProductionOxidative PhosphorylationFatty acidsGlycogenGlucoseATP-storesImmediateSubstrate level phosphorylationAmino acidsAnaerobic GlycolysisAerobic Glycolysis-oxidation

Comparison of Aerobic and Anaerobic ATP productionLimiting FactorsAnaerobic GlycolysisAerobic GlycolysisATP/PCR -oxidationStores -+++ +Aerobic glucose degradation yields 18-19 more ATP than anaerobic, but velocity and rate are lower!

2. glycogen- lactic acid systemAnaerobic metabolism - provides only 2 ATP / glycogen molecule

- reach its maximum rate within few sec.

- energy for further 1.3- 1.6 min

- Accumulated lactic acid fatigue

Physiology of Exercise

.Lactic acid a poisonAfter a while it will make the muscle ache and eventually it will cause cramp, and the muscles will stop working.The athlete has to rest while blood brings fresh supplies of oxygen to the muscles

He/She is repaying back the OXYGEN DEBT.

Physiology of Exercise

Physiology of Exercise

Lactic AcidRegeneration of NAD+ sustains continued operation of glycolysis.Formed from reduction of pyruvate in recycling of NAD or when insufficient O2 is available for pyruvate to enter TCA cycle.

If NADH + H+ cant pass H+ to mitochondria, H+ is passed to pyruvate to form lactate.

Pyruvate:Lactate

Exercise Intensity DomainsModerate ExerciseAll work rates below LTHeavy Exercise: Lower boundary: Work rate at LT Upper boundary: highest work rate at which blood lactate can be stabilized (Maximum lactate steady state)Severe Exercise: Neither O2 or lactate can be stabilized

Oxygen Uptake and Exercise Domains2012Time (minutes) 2442 150 Work Rate (Watts)INCREMENTALCONSTANT LOADModerateHeavyTLacWa300VO2 (l/min)SevereModerateHeavySevere04

Lactate and Exercise Domains

Lactate Threshold

Blood Lactate as a Function of TrainingBlood Lactate (mM)Percent of VO2max255075100

Lactate ThresholdLT as a % of VO2max or workloadSedentary individual 40-60% VO2maxEndurance-trained > 70% VO2maxLT: Maximal lactate at Steady State exerciseMax intensity SS-exercise can be maintainedPrescribe intensity as % of LT

Other Lactate Threshold Terminology Anaerobic threshold or ATfirst used in 1964based on blood La- being associated with hypoxia Should not be used Onset of blood lactate accumulation (OBLA)maximal steady state blood lactate concentrationCan vary between 3 to 7 mmol/LUsually assumed to be around 4 mmol/L

What is the Lactate Threshold (LT)? Point La- production exceeds removal in blood La- rises in a non-linear fashion Rest [La-] 1 mmol/L blood (max 12-15 mmol) LT represents metabolism glycogenolysis and glycolytic metabolism recruitment of fast-twitch motor units Mitochondrial capacity for pyruvate is exceeded Pyruvate converted to lactate to maintain NAD+ Redox potential (NAD+/NADH)

Blood CatecholsReduced Removal of LactateLow Muscle O2Mechanisms to Explain LT

Formation of Lactate is Critical to Cellular FunctionDoes not cause acidosis related to fatiguepH in body too high for Lactic Acid to be formedAssists in regenerating NAD+ (oxidizing power)No NAD+, no glycolysis, no ATPRemoves H+ when it leaves cell: proton consumerHelps maintain pH in muscleCan be converted to glucose/glycogen in liver via Cori cycle

3. Aerobic system :-. (Oxidative metabolism)

Oxidation of food stuffs to provide energy .

Energy so produced is used to power the muscle activity as well as replenish the depleted sources of ATP

ATP produced here is also used to convert lactic acid in the muscles back to pyruvic acid.

This system can power muscle activty as long as nutrients last.

Phosphocreatine ----------- creatine + PO3`` +EnergyGlycogen ------------------- Lactic acid + EnergyGlucoseFatty acids + O2 ---- CO2 + Water +/_ ureaAmino acids + Energy

ATP --- ADP ---- AMP

Physiology of ExerciseNL JonesMacMasters University

Aerobic metabolism - provides 38 ATP / glycogen molecule

- capable of providing great deal of E.

- limited by the bodys ability to supply oxygen & other nessasary nutrients

Physiology of ExerciseAerobic metabolism6 Glucose + 6 O2 = 6 CO2 + H2O

Physiology of Exercise

b) fat metabolism - metabolized via oxydation & enter Krebs cycle & ETC - A typical fatty acid (palmitate) yield about 129 molecules of ATP - A slow process - important at rest, in prolong exercise & in post exercise period

EXHAUSTION - ?

Recovery of the muscle metabolic system after Exercise

Recovery of Aerobic system

Recovery of muscle Glycogen

Oxygen Deficit and DebtOxygen deficit = difference between the total oxygen used during exercise and the total that would have been used if if use had achieved steady state immediatelyOxygen debt = total oxygen used during the recovery period

Recovery VO2 or Excess Post-exercise O2 Consumption (EPOC)Fast component (Alactacid debt) = when prior exercise was primarily aerobic; repaid within 30 to 90 sec; restoration of ATP and CP depleted during exercise.Slow component (Lactacid debt) = reflects strenuous exercise; may take up to several hours to repay; may represent reconversion of lactate to glycogen and restoration of core temperature.

Oxygen Deficit and Debt

Oxygen StoresAir in the lungs 0.5 lDissolved in the body fluids 0.25 lCombined with Hb 1 lBind to myoglobin in the muscles 0.3 lIn heavy exercise this is used within a minute.Extra oxygen to be repaid is about 11.5 l

Energy and Types of Physical ActivitiesEach physical activity or sport you undertake requires a different energy systemTrack Events and their use of Aerobic RespirationBasketball players use both systems Some use mainly aerobic respiration.Others use mainly anaerobic respiration.Most use a combination of the two.Less than 1%100 m10%200 m20%400 m50%800 m60%1,500 m83%5,000 m95%10,000 m100%Marathon

EventPercentage of Aerobic Respiration

Substrate metabolism Glucose /Glycogen Glycolysis Pyruvic acid Lactic acid Fatty acids Acetyl Co A Krebs cycle Elec. T.C

Physiology of ExerciseATP as the Energy Source

The muscles of the body use both carbohydrates and fats to produce energy. The following diagram shows how carbohydrates are used.Making Energy Available to the Cells of the Body Carbohydrates in the form of starch gained from foods such as pasta, bread and potatoes are eaten.The starch is digested in the gut and turned into glucose molecules.The glucose enters the small intestine where it passes into the blood.

The glucose is then used in 3 different waysHere some of the glucose is stored as glycogen and used to maintain blood sugar levels.Glucose is stored here as glycogen and is used when the body is working harder.Glucose diffuses easily into the cells and is used to meet their energy demands.Skeletal MuscleLiverBody Cells

Aerobic and Anaerobic ATP ProductionOx-Dep.TCA CycleAcetyl-CoAFADH2NADH+H+ATPPyruvateLactateATP

Muscle types: I, IIa, IIbType I- slow twitch, fatigue resistant, -glycolytic activity, Endurance - prolonged low intensity activity - predominant type in marathon runnersType IIa- fast oxydative glycolyticType IIb-fast twitch, fast glycolytic -Fatigue quickly, primarily anaerobic - important for sprinting & jumping

CVS IN EXERCISEDelivery of O2 and nutrients to the exercising muscles.

Achieved by altering the cardio-respiratory parameters.

Factors O2 / nutrient supply 1. Increase muscle blood flow 2. Increase CO 3. Increase O2 uptake at tissue level

1. Increase muscle blood flow Muscle BF at rest ~ 2 4ml/100g/min During strenuous exercise ~ upto 30 fold ( 100ml/100g/min)

Muscle blood flow Increase mainly due to vasodilatory metabolites such as AMP, adenosine, H+, K+ & phosphate ions acting on pre-capillary sphincters

This overrides the vasoconstrictor effect of nor-adrenaline.

Muscle BF briefly with contraction due to compression of blood vessels but overall it is enhanced by the pumping action of the muscle.

Strong tonic contraction can cause rapid muscle fatigue.

Factors O2 / nutrient supply 2. cardiac out putAt rest 4 6 l /min.

During severe exercise ~ 4 7 times Mechanisms - a. heart rate - psychic stimuli on medulla initially - later by sym. Discharge vagal tone action of PCO2 on medulla

b. venous return - sym. Discharge - muscle pump - thoracic pump

c. contractility - Frank Starling mechanism - sym. discharge / catecholamine

d. SVR - vasodilatation in muscles

3. O2 extraction by tissues diffusion of O2 - vasodilatation in tissues - capillary bed - R/shift of the ODC ( acidosis, PCO2, temp, 2,3 DPG )

3 fold in A-V O2 difference

Increase muscle blood flow

Trained athletes have - lower HR ( vagal tone)

- Greater SV due to hypertrophy of cardiac muscles

- Can have a greater in SV & HR during exercise

Comparision of cardiac function SV (ml) HR (b/min)At rest Non athlete 70 70 Athlete 100 50

Maxi. exercise Non athlete 110 190 Athlete 160 180

Influence of type of exerciseIsometric exercise (length , tension ) - CO - HR - SV slight change - sys. BP - dias. BP - SVR - muscle BF

Isotonic contration ( length , tension ) - CO - HR - SV great - sys. BP - / dias. BP - SVR - muscle BF

Other CVS changesHR & SV to ~ 90% during stren. Exercise CVS func. Is the limiting factor for O2 delivery in coronary BFCereb. BF is maintained constantSplanchnic flow but some BF is maintained to the bowel and kidney.

Cutaneous flow initially due to symp. Activity. Later an additional in BF to skin heat dissipation

Only a moderate in BP occurs with CO. ( due to vasodilatation)

CVS changes after exerciseCO remains elevated until O2 debt is paid.

HR slowly to the basal level.

BP may be subnormal due to accumulation of vasodilator metabolites.

Respiration in Exercise

Average O2 consumption in a young man at rest = 250 ml/min

Under maximal condition it can inc. as follows

untrained average male = 3600 ml/minathletic trained average male = 4000 ml/minmale marathon runners= 5100 ml/min Oxygen consumpton &pulmonary ventilation

Pulmonary physiology during Exercise

Purpose of respiration is to provide O2 to tissues and remove CO2 from them.To accomplish this 4 major events must be regulated.1. Pulmonary ventilation 2. Diffusion of O2 & CO2 between the blood and alveoli 3. Transport of O2 & CO2 in the blood body fluids and to and from the cells 4. Regulation of ventilation

Changes in ventilation

- abrupt initially followed by more gradual

Stimuli initially motor centre activity & afferents from proprioceptors - subsequence rise ? sensitivity of peri. chemorecep to oscillation of PO2 & PCO2

in pul. Ventilation - due to TV & RRBreathing capacity dose not reach the maximum even in stre. exercise.Pulmonary blood flow increases.Hb remains fully saturated with normal lungs.

Ventilation is not a limiting factor for O2 delivery.

Changes in arterial blood gasses - slightPO2 - vent. a slight rise Fall with vigorous exer. if O2 becomes limited

PCO2 May rise initially - lactic acid met. This rise stimulates vent. PCO2 (res.compen)

pH remains relatively constant moderate exer.

CO2 removal from tissues At rest ~ 200ml/min during exercise ~ 8000ml/min - muscle BF - capillary bed - Haldane effect (HHb is a better buffer) - pulm. BF & ventilation

During maximal exercise . . .O2 consumption, CO2 formation and total pulmonary and alveolar ventilation are increased by 20 fold.

1. pulmonary ventilation inc. to 100 110 l/min but MBC is 150 -170 l/min. Difference ? ( VO2 Max the rate of O2 consumption under maximal aerobic metabolism is 45 % greater in marathon runners )

2. O2 diffusing capacity is hugely increased - sluggish pul. Capillaries at rest begins to open during exercise hence inc. pul. BF and inc. O2 diffusion.(trained athlete has more diffusing capacity for O2 during exercise)

3. increased transport of O2 & CO2 in the blood and dissipation of heat is achieved by massive changes in CVS.

4. Ventilation is regulated by stimulatory impulses from - higher centers of brain- joint and muscle proprioceptives that account for the nervous stimulation of the respiratory center and VMC which helps to keep the blood respiratory gases almost normal.

Blood gases during Exercise

CO2 , O2 and pH all kept at near normal values.

So the stimulation for inc. respiration is mainly neurogenic.

Changes in Ventilation : - .

Inc. ventilation ----- inc. influx of O2 to lungsInc. cardiac out put ----- inc. pulmonary BF.Inc. O2 uptake by blood increases O2 carrying capacity

Inc. extraction of O2 by tissues from blood ---- dec. venous O2 tension -- inc. O2 gradient between alveolar PO2 and pulmonary venous capillaries -- inc. O2 diffusion/ unit time.

Net effect :- Amount of O2 entering the blood in a minute jumps from 250 ml to 4000 ml.

Similarly CO2 excretion is increased from 200 ml / min up to 8000 ml / min.

Inc. in uptake of O2 by tissues is proportional to work load up to a maximum. Beyond, O2 consumption levels off and blood lactate level continues to rise finally leading to an OXYGEN DEBT .

Ventilation increases abruptly with onset of exercise (psychic stimuli)then further gradual increase

Increase is mostly in depth (TV) with moderate exerciseBoth TV & rate inc. with more strenuous exercise Ventilation abruptly decreases when exercise ceases then by more gradual decrease? TV ? RR

Hyperventilation ------ inc. alveolar PO2dec. alveolar PCO2

After exercise some grade of hyperventilation continues un till the O2 debt is repaid. (Up to 90 minutes.)During this period 80 % of lactic acid converted to Glycogen and 20 % metabolized to CO2 and water.

During strenuous exercise RQ reaches 1.5 to 2Just after exercise RQ drops to 0.5

Changes in the Tissues :- Max O2 uptake is limited by the max rate at which O2 is transported to mitochondria in the exercising muscle. Arterioles dilated, new capillary beds open up, distance reduced, more O2 easily diffuse to tissues

PO2 drops, ODH curve in steep portion

dec pH, PO2 and inc. PCO2 , Temperature -- ODH shifts to Right

Net effect :- 3 fold inc. in O2 extraction from each unit of blood

CO increased (x 6) ---- 30 fold increase in muscle BF( because

in exercising muscle dec. PO2 & pH , inc. PCO2 & T and accumulation of other vasodilator metabolites)

Velocity of BF ??

Muscle metabolic rate may increase up to 100 fold during exercise.

Body temperatureMaximum efficiency for conversion of energy nutrients tomuscle work 20-25%Rest released as heat

Regulated by - resetting the thermostat - body temp. - heat loss (vasodilation/ sweating / resp.)

Maximal O2 consumptionAs work rate Vo2

Upper limit to O2 uptake +

Above a certain work rate O2 consumption reaches a plateau. Maximal O2 uptake (Vo2max)

VO2 max is the rate of oxygen consumption under maximal aerobic metabolism.

Greater in a trained person.

This is believed to be partly genetically determined .

Factors that limit Vo2max 1. pulmonary limitation - exercising at high altitude - asthma/ COAD

2. Cardiac out put - Beta blokadeDelivery of O2 through BF most imprt. limiting factor

3. O2 carrying capacity of blood - anaemia (fatigue / SOB)

4. Skeletal muscle limitations - level if mitochondrial enzymes & - capillary density

Anaerobic threshold - the level of exercise at which the anaerobic metabolism commences

- aerobic re-synthesis of energy is insufficient to meet the demand accumulation of lactic acid

Fate of lactate Lactate in blood H+ / lactate- Lactic acidosis

Lactate mostly (80%) converted to glucose in liver replenish glycogen stores pyruvic acid & metabolized oxida.

Oxygen debtThe amount by which O2 consumption exceeds basal consumption at the end of exercise until return to pre- exercise level

O2 is used for - metabolism of lactates - resynthesis of ATP / PCr in muscles - restoration of O2 in body stores

Exercise training VO2max during exercise by - CO - oxygen extraction (capillary bed) - number of mitochondria & enzymes

These will the anaerobic threshold & the exercise capacity.

Sex differences : -

The maximum values of Muscle strength Pulmonary ventilation Cardiac out put

the women can achieve are only 60 -75% of that of the men.

But strength / cm2 almost equal.

Influence of Gender, Initial Fitness Level, and GeneticsMen and women respond similarly to training programsTraining improvement is always greater in individuals with lower initial fitnessGenetics plays an important role in how an individual responds to training

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