overview and basics of exercise physiology quiona stephens, phd, department of military and...
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Overview and Overview and Basics of Exercise Basics of Exercise
PhysiologyPhysiology
Quiona Stephens, PhD, Quiona Stephens, PhD, Department of Military and Department of Military and
Emergency MedicineEmergency Medicine
Topics to CoverTopics to Cover
• Basic DefinitionsBasic Definitions
• Physiologic Responses to ExercisePhysiologic Responses to Exercise
• Maximal Aerobic Capacity and Maximal Aerobic Capacity and Exercise TestingExercise Testing
• Energy SystemsEnergy Systems
• Skeletal Muscle Fiber TypesSkeletal Muscle Fiber Types
• Terms and Concepts Associated Terms and Concepts Associated with Exercisewith Exercise
Pulmonary VentilationPulmonary Ventilation
• Minute ventilation or VE (L/min) = Tidal Minute ventilation or VE (L/min) = Tidal volume (L/breathing) X Breathing rate volume (L/breathing) X Breathing rate (Breaths/min)(Breaths/min)
• Measure of volume of air passing through Measure of volume of air passing through pulmonary system:air expired/minutepulmonary system:air expired/minute
VariablesVariables Tidal VolumeTidal Volume
(L/breathing)(L/breathing)
Breathing RateBreathing Rate
(breaths/min)(breaths/min)
RestRest 10 - 1410 - 14 10 – 2010 – 20
Maximal Maximal ExerciseExercise
100 – 180100 – 180 40 - 60 40 - 60
Relation Between Relation Between Breathing and VentilationBreathing and Ventilation
20
30
40
50
60
Bre
ath
s/M
inu
te
80 100 120 140 160 180Heart Rate
1.0
1.5
2.0
2.5
3.0
3.5
Tid
al v
olu
me
(L
/Bre
ath
)
10
20
30
40
50
60
70
VO
2 (
ml/k
g/m
in)
80 100 120 140 160 180
Heart Rate
0
50
100
150
200
VE
(L
/min
)
Stroke Volume (SV)Stroke Volume (SV)
• Amount of blood ejected from heart Amount of blood ejected from heart with each beat (ml/beat). with each beat (ml/beat).
RestRest Exercise (max)Exercise (max) Max occursMax occurs
80 – 9080 – 90 110 – 200110 – 200(Depending on (Depending on training status)training status)
40-50% of VO40-50% of VO22 max max
untraineduntrained
Up to 60% VOUp to 60% VO22 maxmax
in athletesin athletes
Cardiac Output (CO)Cardiac Output (CO)
• Amount of blood ejected from Amount of blood ejected from heart each min (L/min). heart each min (L/min).
• Stroke Volume x Heart RateStroke Volume x Heart Rate Fick Equation: Fick Equation:
CO = VOCO = VO22/(a - v O/(a - v O22)) Rest: ~ 5 L/minRest: ~ 5 L/min Exercise: ~10 to 25 L/minExercise: ~10 to 25 L/min
• Primary Determinant = Heart ratePrimary Determinant = Heart rate
Relation Between SV and CORelation Between SV and CO
Cardiac Output = SV x HRRest: ~ 5.0 L/minMaximal Exercise: up to 30 L/min
60
80
100
120
140
160
Str
oke
Vo
lum
e (m
l/bea
t)
50
80
110
140
170
200
Hea
rt R
ate
(bp
m)
0 20 40 60 80 100
% of Maximal Oxygen Uptake
05
10152025303540
Car
dia
c O
utp
ut
(L/m
in)
0 20 40 60 80 100
Maximal Aerobic PowerMaximal Aerobic Power (VO (VO2 max2 max))
• Also known as oxygen consumption, oxygen Also known as oxygen consumption, oxygen uptake, and cardiorespiratory fitness.uptake, and cardiorespiratory fitness.
• Greatest amount of OGreatest amount of O22 a person can use during a person can use during physical exercise.physical exercise.
• Ability to take in, transport and deliver OAbility to take in, transport and deliver O22 to to skeletal muscle for use by tissue.skeletal muscle for use by tissue.
• Expressed as liters (L) /min or ml/kg/min.Expressed as liters (L) /min or ml/kg/min.
Assessing VOAssessing VO22
• Direct Measure: Rearrange Fick Equation: VODirect Measure: Rearrange Fick Equation: VO22 = =
CO X (a - vCO X (a - vO2O2))
• Indirect Measure: gas exchange at mouth: VOIndirect Measure: gas exchange at mouth: VO22 = =
VVEE X (F X (FIO2IO2 - F - FEO2EO2))
Rest: 0.20 to 0.35 L/minRest: 0.20 to 0.35 L/min Maximal Exercise: 2 to 6 L/minMaximal Exercise: 2 to 6 L/min
Importance of Importance of VOVO2 max2 max
• An index of maximal cardiovascular and An index of maximal cardiovascular and pulmonary function. pulmonary function.
• Single most useful measurement to Single most useful measurement to characterize the functional capacity of the characterize the functional capacity of the oxygen transport system.oxygen transport system.
• Limiting factor in endurance performanceLimiting factor in endurance performance
Determinants of VODeterminants of VO2max2max
• Muscle Blood FlowMuscle Blood Flow
• Capillary DensityCapillary Density
• OO22 Diffusion Diffusion
• OO22 Extraction Extraction
• Hb-OHb-O22 Affinity Affinity
• Muscle Fiber Muscle Fiber ProfilesProfiles
• Cardiac OutputCardiac Output
• Arterial PressureArterial Pressure
• HemoglobinHemoglobin
• VentilationVentilation
• OO22 Diffusion Diffusion
• Hb-OHb-O22 Affinity Affinity
• Alveolar Ventilation Alveolar Ventilation Perfusion ratioPerfusion ratio
Peripheral Factors Central Factors
Factors Affecting VOFactors Affecting VO2max2max
IntrinsicIntrinsic
• GeneticGenetic
• GenderGender
• Body CompositionBody Composition
• Muscle massMuscle mass
• AgeAge
• PathologiesPathologies
ExtrinsicExtrinsic
• Activity LevelsActivity Levels
• Time of DayTime of Day
• Sleep DeprivationSleep Deprivation
• Dietary IntakeDietary Intake
• Nutritional StatusNutritional Status
• EnvironmentEnvironment
Common Criteria Used to Common Criteria Used to Document VODocument VO2 max2 max
• Primary CriteriaPrimary Criteria < 2.1 ml/kg/min increase with 2.5% grade < 2.1 ml/kg/min increase with 2.5% grade
increase often seen as a increase often seen as a plateauplateau in VO in VO22
• Secondary CriteriaSecondary Criteria Blood lactate ≥ 8 mmol/LBlood lactate ≥ 8 mmol/L RER ≥ 1.10RER ≥ 1.10 in HR to 90% of age predictedin HR to 90% of age predicted RPE ≥ 17RPE ≥ 17
Aging, Training, and VOAging, Training, and VO2max2max
0
10
20
30
40
50
60
70
20 30 40 50 60 70Age (yr)
VO
2m
ax (
ml/
kg/m
in)
AthletesModerately ActiveSedentary
Gender, Age and VOGender, Age and VO2max2max
1.5
2.0
2.5
3.0
3.5
4.0V
O2
ma
x
(L/m
in)
10 20 30 40 50 60Age (Years)
Women
Men
Effect of Bed rest on VOEffect of Bed rest on VO2max2max
-40
-30
-20
-10
0
0 10 20 30 40Days of Bedrest
%Decline in VO2max
1.4 - 0.85 X Days; r = - 0.73
Data from VA Convertino MSSE 1997Data from VA Convertino MSSE 1997
% D
eclin
e in
VO
2max
VOVO2max2max Classification Classification for Men for Men (ml/kg/min)(ml/kg/min)
Age Age (yrs)(yrs)
20 - 29
30 - 39
40 - 49
50 - 59
60 - 69
LowLow
<25
<23
<20
<18
<16
FairFair
25 - 33
23 - 30
20 - 26
18 - 24
16 - 22
AverageAverage
34 - 42
31 - 38
27 - 35
25 - 33
23 - 30
GoodGood
43 - 52
39 - 48
36 - 44
34 - 42
31 - 40
HighHigh
53+
49+
45+
43+
41+
VOVO2max2max Classification for Classification for Women Women (ml/kg/min)(ml/kg/min)
Age Age (yrs)(yrs)
20 - 29
30 - 39
40 - 49
50 - 59
60 - 69
LowLow
<24
<20
<17
<15
<13
FairFair
24 - 30
20 - 27
17 - 23
15 - 20
13 - 17
AverageAverage
31 - 37
28 - 33
24 - 30
21 - 27
18 - 23
GoodGood
38 - 48
34 - 44
31 - 41
28 - 37
24 - 34
HighHigh
49+
45+
42+
38+
35+
Respiratory Exchange Respiratory Exchange Ratio/QuotientRatio/Quotient
• Respiratory Exchange Ratio (RER): ratio of CORespiratory Exchange Ratio (RER): ratio of CO22 expired/O expired/O22 consumed consumed Measured by gases exchanged at the mouth.Measured by gases exchanged at the mouth.
• Respiratory Quotient (RQ): ratio of CORespiratory Quotient (RQ): ratio of CO22 produced by cellular produced by cellular metabolism to Ometabolism to O22 used by tissues used by tissues Measurements are made at cellular levelMeasurements are made at cellular level
• Useful indicator of type of substrate (fat vs. carbohydrate) Useful indicator of type of substrate (fat vs. carbohydrate) being metabolized: being metabolized: Fat is the first fuel source used during exercise. As RQ/RER Fat is the first fuel source used during exercise. As RQ/RER
increases towards 1.0 the use of CHO as energy increases.increases towards 1.0 the use of CHO as energy increases.
• RER/RQ typically ranges from .70 to 1.0RER/RQ typically ranges from .70 to 1.0++
Estimating Maximal Estimating Maximal Heart RateHeart Rate
• OLD FORMULA: 220 – ageOLD FORMULA: 220 – age
• NEW FORMULA: 208 - 0.7 X ageNEW FORMULA: 208 - 0.7 X age New formula may be more accurate for older persons and is New formula may be more accurate for older persons and is
independent of gender and habitual physical activity independent of gender and habitual physical activity
• Estimated maximal heart rate may be 5 to 10% (10 to 20 Estimated maximal heart rate may be 5 to 10% (10 to 20 bpm) > or < actual value. bpm) > or < actual value.
AgeAge Old FormulaOld Formula New FormulaNew Formula
6060 160160 166166
4040 180180 180180
2020 200200 194194
Typical Ways to Measure Typical Ways to Measure VOVO2max2max
• Treadmill (walking/running)Treadmill (walking/running)
• Cycle ErgometryCycle Ergometry
• Arm ErgometryArm Ergometry
• Step TestsStep Tests
Maximal Values Achieved Maximal Values Achieved During Various Exercise TestsDuring Various Exercise Tests
Types of ExerciseTypes of Exercise
Uphill RunningUphill RunningHorizontal RunningHorizontal RunningUpright CyclingUpright CyclingSupine CyclingSupine CyclingArm CrankingArm CrankingArms and LegsArms and LegsStep TestStep Test
% of% of VOVO2max2max
100%100%95 - 98%95 - 98%93 - 96%93 - 96%82 - 85%82 - 85%65 - 70%65 - 70%
100 - 104%100 - 104%97% 97%
Energy Systems Energy Systems for Exercisefor Exercise
Energy SystemsMole of
ATP/minTime to Fatigue
Immediate: Phosphagen (Phosphocreatine and ATP)
4 5 to 10 sec
Short Term: Glycolytic
(Glycogen-Lactic Acid)2.5 1.0 to 1.6 min
Long Term: Aerobic 1Unlimited
time
Anaerobic vs. Aerobic Anaerobic vs. Aerobic Energy SystemsEnergy Systems
• AnaerobicAnaerobic ATP-CP : ≤ 10 sec.ATP-CP : ≤ 10 sec. Glycolysis: A few minutesGlycolysis: A few minutes
• AerobicAerobic Krebs cycleKrebs cycle Electron Transport ChainElectron Transport Chain
2 minutes +
Energy Systems
100%%
Cap
acit
y o
f E
ner
gy
Sys
tem
10 sec 30 sec 2 min 5+ min
Energy Transfer Systems and Exercise
Aerobic Energy System
Anaerobic Glycolysis
ATP - CP
Exercise Time
Skeletal Muscle Fiber TypesSkeletal Muscle Fiber Types
• Fast-TwitchFast-Twitch
Type IIaType IIa
Type IId(x)Type IId(x)
• Slow-TwitchSlow-Twitch
Type IType I
Skeletal Muscle Fiber TypesSkeletal Muscle Fiber Types
• Characterized by differences in morphology, Characterized by differences in morphology, histochemistry, enzyme activity, surface histochemistry, enzyme activity, surface characteristics, and functional capacity.characteristics, and functional capacity.
• Distribution shows adaptive potential in response Distribution shows adaptive potential in response to neuronal activity, hormones, training/functional to neuronal activity, hormones, training/functional demands, and aging. demands, and aging.
• Change in a sequential manner from either slow to Change in a sequential manner from either slow to fast or fast to slow.fast or fast to slow.
Skeletal Muscle
Characteristics of Human Characteristics of Human Muscle Fiber TypesMuscle Fiber Types
Other Terminology Slow Twitch Fast Twitch
Type Ia Type lla Type lld(x)
Aerobic Capacity HIGH MED/HIGH MED
Myoglobin Content HIGH MED LOW
Color RED RED PINK/WHITE
Fatigue Resistance HIGH MED/HIGH MED
Glycolytic Capacity LOW MED MED/HIGH
Glycogen Content LOW MED HIGH
Triglyceride Content HIGH MED MED/LOW
Myosin Heavy Chain (MHC) MHCIb MHCIIa MHCIId(x)
Terms and Concepts Terms and Concepts Associated with ExerciseAssociated with Exercise
• Rating of Perceived ExertionRating of Perceived Exertion
• Training Heart RateTraining Heart Rate
• Energy ExpenditureEnergy Expenditure
• Thresholds and Exercise DomainsThresholds and Exercise Domains
• OO22 Deficit and Excess Post-Exercise Deficit and Excess Post-Exercise
OO22 Consumption Consumption
Rating of Perceived Rating of Perceived Exertion: RPE/Borg ScaleExertion: RPE/Borg Scale
678910111213141516171819
Very, very light
Very light
Fairly light
Somewhat hard
Hard
Very hard
Very, very hard
Lactate Threshold
2.0 mM Lactate
2.5 mM Lactate
4.0 mM Lactate
Approaches to Determining Approaches to Determining Training Heart RateTraining Heart Rate
• 60 to 90% of Maximal HR60 to 90% of Maximal HR Max HR = 180Max HR = 180 60% = 108 and 90% = 16260% = 108 and 90% = 162
• 50 to 85% of Heart Rate Reserve50 to 85% of Heart Rate Reserve Max HR = 180 and Resting HR = 70Max HR = 180 and Resting HR = 70 HRR = 180 - 70 = 110HRR = 180 - 70 = 110 50% = 70 + 65 = 135; 85% = 94 + 70 = 164 50% = 70 + 65 = 135; 85% = 94 + 70 = 164
• Plot HR vs. OPlot HR vs. O22 Uptake or Exercise Intensity Uptake or Exercise Intensity
Heart Rate and VOHeart Rate and VO2max2max
0 20 40 60 80 100
% of VO2max
30
40
50
60
70
80
90
100%
of
Ma
xim
al H
ea
rt R
ate
Energy ExpenditureEnergy Expenditure
• MET: Energy cost as a multiple of resting MET: Energy cost as a multiple of resting metabolic ratemetabolic rate 1 MET = energy cost at rest ~3.5 ml of O1 MET = energy cost at rest ~3.5 ml of O22/kg/min/kg/min
3 MET = 10.5 ml of O3 MET = 10.5 ml of O22 /kg/min /kg/min
6 MET = 21.0 ml of O6 MET = 21.0 ml of O22 /kg/min /kg/min
• 1 L/min of O1 L/min of O2 2 isis ~ 5 kcal/L ~ 5 kcal/L
VOVO2 2 (L/min) ~ 5 kcal/L = kcal/min(L/min) ~ 5 kcal/L = kcal/min
• 1 MET = 0.0175 kcal/kg/min1 MET = 0.0175 kcal/kg/min
Lactate/Lactic AcidLactate/Lactic Acid
• A product of glycolysis formed from reduction of A product of glycolysis formed from reduction of pyruvate in recycling of NAD or when insufficient pyruvate in recycling of NAD or when insufficient OO22 is available for pyruvate to enter the TCA is available for pyruvate to enter the TCA cycle. cycle.
• Extent of lactate formation depends on Extent of lactate formation depends on availability of both pyruvate and NADH.availability of both pyruvate and NADH.
• Blood lactate at rest is about 0.8 to 1.5 mM, but Blood lactate at rest is about 0.8 to 1.5 mM, but during intense exercise can be in excess of 18 during intense exercise can be in excess of 18
mM.mM.
Lactate ThresholdLactate Threshold
• Intensity of exercise at which blood lactate Intensity of exercise at which blood lactate concentration is 1 mM above baseline.concentration is 1 mM above baseline.
• Expressed as a function of VOExpressed as a function of VO2max, 2max, i.e., 65% i.e., 65%
of VOof VO2max2max..
• Expressed as a function of velocity or Expressed as a function of velocity or power output, i.e., 150 W or 7.5 mph.power output, i.e., 150 W or 7.5 mph.
0
4
8
12
16
0 1000 2000 3000 4000 5000
Oxygen Uptake (ml/min)
Lactate ThresholdLactate Threshold
1.0 mM above baseline1.0 mM above baseline
Blood Lactate as a Blood Lactate as a Function of TrainingFunction of Training
Blo
od
La
cta
te (
mM
)
Percent of VO2max
25 50 75 100
Ventilatory ThresholdVentilatory Threshold
• Describes the point at which pulmonary Describes the point at which pulmonary ventilation increases disproportionately ventilation increases disproportionately with oxygen consumption during graded with oxygen consumption during graded exercise.exercise.
• At this exercise intensity, pulmonary At this exercise intensity, pulmonary ventilation no longer links tightly to ventilation no longer links tightly to oxygen demand at the cellular level.oxygen demand at the cellular level.
Ventilatory ThresholdVentilatory Threshold
1000
2000
3000
4000
5000
6000
2000 2500 3000 3500 4000 4500
VO 2 (ml/min)
AT
By V Slope Method
Ventilatory ThresholdVentilatory Threshold
80 100 120 140 160 180
Heart Rate
0
50
100
150
200
VE
(L
/min
)
By Minute Ventilation Method
Exercise Intensity DomainsExercise Intensity Domains
• Moderate ExerciseModerate Exercise All work rates below LTAll work rates below LT
• Heavy Exercise: Heavy Exercise: Lower boundary: Work rate at LT Lower boundary: Work rate at LT Upper boundary: highest work rate at which Upper boundary: highest work rate at which
blood lactate can be stabilized (Maximum blood lactate can be stabilized (Maximum lactate steady state)lactate steady state)
• Severe Exercise: Severe Exercise: Neither ONeither O22 or lactate can be stabilized or lactate can be stabilized
Oxygen Uptake and Oxygen Uptake and Exercise DomainsExercise Domains
2
00 1212
Time (minutes) 24
4
2
150 Work Rate (Watts)Work Rate (Watts)
INCREMENTAL CONSTANT LOAD
ModerateModerate
HeavyHeavy
TLac Wa
300
VO
2 (L
/min
)
SevereSevereModerateModerate
HeavyHeavy
SevereSevere
00
4
Lactate and Exercise Lactate and Exercise Domains Domains
0
6
12
0 12 24
Time (minutes)
Heavy
Moderate
Severe
Oxygen Deficit and Debt/EPOCOxygen Deficit and Debt/EPOC
• OO22 Deficit Deficit = difference between total O = difference between total O22 used used during exercise and total that would have during exercise and total that would have been used if steady state had been achieved been used if steady state had been achieved immediatelyimmediately
• Excess Post-Exercise OExcess Post-Exercise O22 Consumption Consumption (EPOC) or O(EPOC) or O22 debt debt = increased rate of O = increased rate of O22 used used during recovery period. during recovery period. The extra oxygen is The extra oxygen is used in the processes that restore the body to used in the processes that restore the body to a resting state and adapt it to the exercise just a resting state and adapt it to the exercise just performed. performed.
Oxygen Deficit and DebtOxygen Deficit and Debt
EPOC or Recovery VOEPOC or Recovery VO22
Fast componentFast component (Alactacid debt??) = when (Alactacid debt??) = when prior exercise was primarily aerobic; repaid prior exercise was primarily aerobic; repaid within 30 to 90 sec; restoration of ATP and within 30 to 90 sec; restoration of ATP and CP depleted during exercise.CP depleted during exercise.
Slow componentSlow component (Lactacid debt) = reflects (Lactacid debt) = reflects strenuous exercise; may take up to several strenuous exercise; may take up to several hours to repay; may represent re-conversion hours to repay; may represent re-conversion of lactate to glycogen.of lactate to glycogen.
Things to remember:Things to remember:
• Know the basic definitions & normal valuesKnow the basic definitions & normal values
• Understand VOUnderstand VO2 max2 max
• Recognize differences in terms often used Recognize differences in terms often used interchangeablyinterchangeably
• Review energy systems for exercise Review energy systems for exercise
• Be familiar w/ terms & concepts associated Be familiar w/ terms & concepts associated w/ exercise w/ exercise
Questions???Questions???