Presentation on theme: "Overview and Basics of Exercise Physiology"— Presentation transcript:
1Overview and Basics of Exercise Physiology Quiona Stephens, PhD, Department of Military and Emergency Medicine
2Topics to Cover Basic Definitions Physiologic Responses to Exercise Maximal Aerobic Capacity and Exercise TestingEnergy SystemsSkeletal Muscle Fiber TypesTerms and Concepts Associated with Exercise
3Pulmonary Ventilation Minute ventilation or VE (L/min) = Tidal volume (L/breathing) X Breathing rate (Breaths/min)Measure of volume of air passing through pulmonary system:air expired/minuteVariablesTidal Volume(L/breathing)Breathing Rate(breaths/min)Rest10 – 20Maximal Exercise100 – 180
4Relation Between Breathing and Ventilation 2030405060Breaths/Minute80100120140160180Heart Rate1.01.52.02.53.03.5Tidal volume (L/Breath)200706015050VO2 (ml/kg/min)VE (L/min)100403050201080100120140160180Heart Rate
5(Depending on training status) Stroke Volume (SV)Amount of blood ejected from heart with each beat (ml/beat).RestExercise (max)Max occurs80 – 90110 – 200(Depending on training status)40-50% of VO2 max untrainedUp to 60% VO2 max in athletes
6Cardiac Output (CO)Amount of blood ejected from heart each min (L/min).Stroke Volume x Heart RateFick Equation: CO = VO2/(a - v O2)Rest: ~ 5 L/minExercise: ~10 to 25 L/minPrimary Determinant = Heart rate
7Relation Between SV and CO Cardiac Output = SV x HRRest: ~ 5.0 L/minMaximal Exercise: up to 30 L/min6080100120140160Stroke Volume (ml/beat)50110170200Heart Rate (bpm)2040% of Maximal Oxygen Uptake51015253035Cardiac Output (L/min)
8Maximal Aerobic Power (VO2 max) Also known as oxygen consumption, oxygen uptake, and cardiorespiratory fitness.Greatest amount of O2 a person can use during physical exercise.Ability to take in, transport and deliver O2 to skeletal muscle for use by tissue.Expressed as liters (L) /min or ml/kg/min.
9Assessing VO2Direct Measure: Rearrange Fick Equation: VO2 = CO X (a - vO2)Indirect Measure: gas exchange at mouth: VO2 = VE X (FIO2 - FEO2)Rest: 0.20 to 0.35 L/minMaximal Exercise: 2 to 6 L/min
10Importance of VO2 maxAn index of maximal cardiovascular and pulmonary function.Single most useful measurement to characterize the functional capacity of the oxygen transport system.Limiting factor in endurance performance
11Determinants of VO2max Peripheral Factors Central Factors Muscle Blood FlowCapillary DensityO2 DiffusionO2 ExtractionHb-O2 AffinityMuscle Fiber ProfilesCardiac OutputArterial PressureHemoglobinVentilationO2 DiffusionHb-O2 AffinityAlveolar Ventilation Perfusion ratio
13Common Criteria Used to Document VO2 max Primary Criteria< 2.1 ml/kg/min increase with 2.5% grade increase often seen as a plateau in VO2Secondary CriteriaBlood lactate ≥ 8 mmol/LRER ≥ 1.10in HR to 90% of age predictedRPE ≥ 17
14Aging, Training, and VO2max 70Athletes60Moderately ActiveSedentary5040VO2max (ml/kg/min)302010203040506070Age (yr)
15Gender, Age and VO2max 4.0 Men Women 3.5 VO2max (L/min) 3.0 2.5 2.0 1.5102030405060Age (Years)
16Effect of Bed rest on VO2max %Decline in VO2maxX Days; r =-10% Decline in VO2max-20-30-4010203040Days of BedrestData from VA Convertino MSSE 1997
17VO2max Classification for Men (ml/kg/min) Age (yrs)Low<25<23<20<18<16FairAverageGoodHigh53+49+45+43+41+
18VO2max Classification for Women (ml/kg/min) Age (yrs)Low<24<20<17<15<13FairAverageGoodHigh49+45+42+38+35+
19Respiratory Exchange Ratio/Quotient Respiratory Exchange Ratio (RER): ratio of CO2 expired/O2 consumedMeasured by gases exchanged at the mouth.Respiratory Quotient (RQ): ratio of CO2 produced by cellular metabolism to O2 used by tissuesMeasurements are made at cellular levelUseful indicator of type of substrate (fat vs. carbohydrate) being metabolized:Fat is the first fuel source used during exercise. As RQ/RER increases towards 1.0 the use of CHO as energy increases.RER/RQ typically ranges from .70 to 1.0+
20Estimating Maximal Heart Rate OLD FORMULA: 220 – ageNEW FORMULA: X ageNew formula may be more accurate for older persons and is independent of gender and habitual physical activityEstimated maximal heart rate may be 5 to 10% (10 to 20 bpm) > or < actual value.AgeOld FormulaNew Formula601601664018020200194
21Typical Ways to Measure VO2max Treadmill (walking/running)Cycle ErgometryArm ErgometryStep Tests
22Maximal Values Achieved During Various Exercise Tests Types of ExerciseUphill RunningHorizontal RunningUpright CyclingSupine CyclingArm CrankingArms and LegsStep Test% of VO2max100%%%%%%97%
23Energy Systems for Exercise Mole of ATP/minTime to FatigueImmediate: Phosphagen (Phosphocreatine and ATP)45 to 10 secShort Term: Glycolytic(Glycogen-Lactic Acid)2.51.0 to 1.6 minLong Term: Aerobic1Unlimited time
24Anaerobic vs. Aerobic Energy Systems ATP-CP : ≤ 10 sec.Glycolysis: A few minutesAerobicKrebs cycleElectron Transport Chain2 minutes +
26Energy Transfer Systems and Exercise 100%% Capacity of Energy SystemAnaerobic GlycolysisAerobic Energy SystemATP - CP10 sec30 sec2 min5+ minExercise Time
27Skeletal Muscle Fiber Types Fast-TwitchType IIaType IId(x)Slow-TwitchType I
28Skeletal Muscle Fiber Types Characterized by differences in morphology, histochemistry, enzyme activity, surface characteristics, and functional capacity.Distribution shows adaptive potential in response to neuronal activity, hormones, training/functional demands, and aging.Change in a sequential manner from either slow to fast or fast to slow.
30Characteristics of Human Muscle Fiber Types Other TerminologySlow TwitchFast TwitchType IaType llaType lld(x)Aerobic CapacityHIGHMED/HIGHMEDMyoglobin ContentLOWColorREDPINK/WHITEFatigue ResistanceGlycolytic CapacityGlycogen ContentTriglyceride ContentMED/LOWMyosin Heavy Chain (MHC)MHCIbMHCIIaMHCIId(x)
31Terms and Concepts Associated with Exercise Rating of Perceived ExertionTraining Heart RateEnergy ExpenditureThresholds and Exercise DomainsO2 Deficit and Excess Post-Exercise O2 Consumption
32Rating of Perceived Exertion: RPE/Borg Scale 678910111213141516171819Very, very lightVery lightFairlylightSomewhat hardHardVeryhardVery, very hardLactate Threshold2.0 mM Lactate2.5 mM Lactate4.0 mM Lactate
33Approaches to Determining Training Heart Rate 60 to 90% of Maximal HRMax HR = 18060% = 108 and 90% = 16250 to 85% of Heart Rate ReserveMax HR = 180 and Resting HR = 70HRR = = 11050% = = 135; 85% = = 164Plot HR vs. O2 Uptake or Exercise Intensity
34Heart Rate and VO2max % of Maximal Heart Rate % of VO2max 100 90 80 70 6050403020406080100% of VO2max
35Energy ExpenditureMET: Energy cost as a multiple of resting metabolic rate1 MET = energy cost at rest ~3.5 ml of O2/kg/min3 MET = 10.5 ml of O2 /kg/min6 MET = 21.0 ml of O2 /kg/min1 L/min of O2 is ~ 5 kcal/LVO2 (L/min) ~ 5 kcal/L = kcal/min1 MET = kcal/kg/min
36Lactate/Lactic AcidA product of glycolysis formed from reduction of pyruvate in recycling of NAD or when insufficient O2 is available for pyruvate to enter the TCA cycle.Extent of lactate formation depends on availability of both pyruvate and NADH.Blood lactate at rest is about 0.8 to 1.5 mM, but during intense exercise can be in excess of 18 mM.
37Lactate ThresholdIntensity of exercise at which blood lactate concentration is 1 mM above baseline.Expressed as a function of VO2max, i.e., 65% of VO2max.Expressed as a function of velocity or power output, i.e., 150 W or 7.5 mph.
39Blood Lactate as a Function of Training Blood Lactate (mM)255075100Percent of VO2max
40Ventilatory Threshold Describes the point at which pulmonary ventilation increases disproportionately with oxygen consumption during graded exercise.At this exercise intensity, pulmonary ventilation no longer links tightly to oxygen demand at the cellular level.
43Exercise Intensity Domains Moderate ExerciseAll work rates below LTHeavy Exercise:Lower boundary: Work rate at LTUpper boundary: highest work rate at which blood lactate can be stabilized (Maximum lactate steady state)Severe Exercise:Neither O2 or lactate can be stabilized
44Oxygen Uptake and Exercise Domains LCONSTANTLOADTLacWSeverea44HeavyVO2 (L/min)Severe22ModerateHeavyModerate1503001224Work Rate (Watts)Time (minutes)
46Oxygen Deficit and Debt/EPOC O2 Deficit = difference between total O2 used during exercise and total that would have been used if steady state had been achieved immediatelyExcess Post-Exercise O2 Consumption (EPOC) or O2 debt = increased rate of O2 used during recovery period. The extra oxygen is used in the processes that restore the body to a resting state and adapt it to the exercise just performed.
48EPOC or Recovery VO2Fast 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 re-conversion of lactate to glycogen.
49Things to remember: Know the basic definitions & normal values Understand VO2 maxRecognize differences in terms often used interchangeablyReview energy systems for exerciseBe familiar w/ terms & concepts associated w/ exercise