3.+aerobic+capaciy+and+endurance (1)

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Aerobic Capacity and Endurance

Research Center in Physical Acitivity , Health and Leisure, University of Porto

School of Health, Faculty of Health Sciences, Fernando Pessoa University

José António Lumini

[email protected]

Exercise Physiology

• The study of the effects of exercise on the body.

• Body’s responses and adaptations to exercises

– System to subcellular level

– Acute (short term) to chronic (long term) adaptations

• Population served

– Elite performers

– People of all ages and abilities, diseased or not, in leisure, sports and health contexts

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•What is exercise physiology?

•What is the role of physical activity and exercise in achieving physical fitness and health?

•How do you use the FITT formula to design a fitness program?

•What are the contributors and deterrents

to fitness?

Fitness is a general term used to describe the ability to perform

physical work.

Performing physical work requires cardiorespiratory functioning,

muscular strength and endurance, and musculoskeletal flexibility.

In Kisner, C and Colby LA. (2007). Therapeutic exercise: Foundations and techniques

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Pulmonary 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/minute

VariablesTidal Volume

(L/breathing)

Breathing Rate

(breaths/min)

Rest 10 - 14 10 – 20

Maximal Exercise 100 – 180 40 - 60

Relation Between Breathing and

Ventilation

20

30

40

50

60

Bre

ath

s/M

inu

te

80 100 120 140 160 180

Heart Rate

1.0

1.5

2.0

2.5

3.0

3.5

Tid

al v

olu

me (

L/B

reath

)

10

20

30

40

50

60

70

VO

2(m

l/kg

/min

)

80 100 120 140 160 180

Heart Rate

0

50

100

150

200

VE

(L

/min

)

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Stroke Volume (SV)

• Amount of blood ejected from heart with each

beat (ml/beat).

Rest Exercise (max) Max occurs

80 – 90 110 – 200

(Depending on training

status)

40-50% of VO2 max

untrained

Up to 60% VO2 max in

athletes

Cardiac Output (CO)

• Amount of blood ejected from heart each min (L/min).

• Stroke Volume x Heart Rate

– Fick Equation: CO = VO2/(a - v O2)

– Rest: ~ 5 L/min

– Exercise: ~10 to 25 L/min

• Primary Determinant = Heart rate

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Exercise:

↑ Heart Rate

↑ Stroke volume

↑ Blood pressure

in Willmore, JA. and Costill, DL.(1994).Phsysiology of sport and exercise

Relation 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 (

ml/

be

at)

50

80

110

140

170

200

He

art

Ra

te (

bp

m)

0 20 40 60 80 100

% of Maximal Oxygen Uptake

05

1015

2025

3035

40

Ca

rdia

c O

utp

ut

(L/m

in)

0 20 40 60 80 100

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In Voight et al (2007).Musculoskeletal interventions: techniques for therapeutic exercise


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Maximum oxygen consumption (VO2 max) is a measure of

the body’s capacity to use oxygen.

It is the maximum amount of oxygen consumed per minute

when the individual has reached maximum effort.

Ability to take in, transport and deliver O2 to skeletal muscle for use by tissue.

It is usually expressed relative to body weight, as milliliters of oxygen per

kilogram of body weight per minute (ml/kg per minute).


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VO2max

•Uses a percentage of the maximum rate of oxygen

consumption

•Very time-consuming and complicated measure

•Typically a laboratory measure in hospitals and universities

because of expensive equipment required

•Highly competitive athletes (performance goal category) may

want to pursue such a measure at a university exercise

physiology laboratory to track changes through a training

program.

Oxygen supply to the body involves

the coordinated fuction


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Endurance is the ability to work for prolonged periods of

time and the ability to resist fatigue.

It includes muscular endurance and cardiovascular

endurance.

Cardiovascular endurance refers to the ability to perform

large muscle dynamic exercise, such as walking, swimming,

and/or biking for long periods of time.


Cardiovascular fitness : endurance type activities: fuel challenging

large muscle mass

repetitive

lower intensity

walking, running, swimming, cycling

Muscular strength: high resistance, high force output

focus on muscle groups not on systemic “exercise”

e.g. knee extensors vs. flexors

Can a type of exercise be both strength and endurance?

yes BUT the effectiveness of any one form of activity to elicit

a specific adaptation is dependent on the endurance/strength

starting state of the individual.

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Specificity of Exercise: Adaptations that occur in response to

training are specific to the nature of the training stimulus

Cardiovascular fitness: requires that the person

train in a manner that challenges heart rate, cardiac

output, capillarity … with the underlying change being

improved oxygen delivery to working tissues

Muscular strength: requires that the person train in a manner

that challenges the recruitment and force output of specific

muscle groups … with the underlying change being increased

muscle mass.

The corollary to this is that training for

endurance will not augment strength or vice

versa.

Assessing VO2

• Direct 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/min

– Maximal Exercise: 2 to 6 L/min

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Importance of VO2 max

• An 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

Determinants of VO2max

• Muscle Blood Flow

• Capillary Density

• O2 Diffusion

• O2 Extraction

• Hb-O2 Affinity

• Muscle Fiber Profiles

• Cardiac Output

• Arterial Pressure

• Hemoglobin

• Ventilation

• O2 Diffusion

• Hb-O2 Affinity

• Alveolar Ventilation

Perfusion ratio

Peripheral Factors Central Factors

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Factors Affecting VO2max

Intrinsic

• Genetic

• Gender

• Body Composition

• Muscle mass

• Age

• Pathologies

Extrinsic

• Activity Levels

• Time of Day

• Sleep Deprivation

• Dietary Intake

• Nutritional Status

• Environment

Common 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 VO2

Secondary Criteria

• Blood lactate ≥ 8 mmol/L

• RER ≥ 1.10

• ↑ HR to 90% of age predicted

• RPE ≥ 17

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retalk/wp-content/blogs.dir/7/files/2011/05/diseases/Aerobic_Capacity-2.jpg

0

4

8

12

16

0 1000 2000 3000 4000 5000

Oxygen Uptake (ml/min)

Lactate Threshold

1.0 mM above baseline

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Heart Rate and VO2max

0 20 40 60 80 100

% of VO2max

30

40

50

60

70

80

90

100%

of

Ma

xim

al

He

art

Ra

te

In http://www.escardio.org/

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Aging, Training, and VO2max

0

10

20

30

40

50

60

70

20 30 40 50 60 70

Age (yr)

VO

2m

ax

(ml/

kg

/min

)

Athletes

Moderately Active

Sedentary

Gender, Age and VO2max

1.5

2.0

2.5

3.0

3.5

4.0

VO

2m

ax

(L/m

in)

10 20 30 40 50 60

Age (Years)

Women

Men

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Effect of Bed rest on VO2max

-40

-30

-20

-10

0

0 10 20 30 40

Days of Bedrest

%Decline in VO2max

1.4 - 0.85 X Days; r = - 0.73

In VA Convertino MSSE 1997

% D

ecl

ine

in

VO

2m

ax

VO2max Classification for Men (ml/kg/min)

Age (yrs)

20 - 29

30 - 39

40 - 49

50 - 59

60 - 69

Low

<25

<23

<20

<18

<16

Fair

25 - 33

23 - 30

20 - 26

18 - 24

16 - 22

Average

34 - 42

31 - 38

27 - 35

25 - 33

23 - 30

Good

43 - 52

39 - 48

36 - 44

34 - 42

31 - 40

High

53+

49+

45+

43+

41+

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VO2max Classification for Women (ml/kg/min)

Age (yrs)

20 - 29

30 - 39

40 - 49

50 - 59

60 - 69

Low

<24

<20

<17

<15

<13

Fair

24 - 30

20 - 27

17 - 23

15 - 20

13 - 17

Average

31 - 37

28 - 33

24 - 30

21 - 27

18 - 23

Good

38 - 48

34 - 44

31 - 41

28 - 37

24 - 34

High

49+

45+

42+

38+

35+

Respiratory Exchange Ratio/Quotient

• Respiratory Exchange Ratio (RER): ratio of CO2 expired/O2consumed

- Measured by gases exchanged at the mouth.

• Respiratory Quotient (RQ): ratio of CO2 produced by cellular metabolism to O2 used by tissues

-Measurements are made at cellular level

• Useful 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+

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Typical Ways to Measure VO2max

• Treadmill (walking/running)

• Cycle Ergometry

• Arm Ergometry

• Step Tests

Maximal Values During Various

Exercise Tests

Types of Exercise

Uphill Running

Horizontal Running

Upright Cycling

Supine Cycling

Arm Cranking

Arms and Legs

Step Test

% of VO2max

100%

95 - 98%

93 - 96%

82 - 85%

65 - 70%

100 - 104%

97%

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Cardiopulmonary Exercise Testing (CPET)

Cardiopulmonary exercise testing (CPX, CPEX or CPET) is the 'gold

standard' tool for the evaluation of cardiopulmonary function and

fitness. It is an entirely non-invasive and objective method of

assessing the exercise response of the pulmonary,

cardiovascular and skeletal muscle systems.

CPET evaluates the way in which your heart, lungs and circulation

simultaneously respond to exercise.

Laboratory Tests

Maximal

Sub-maximal

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Field Tests

Maximal

Sub-maximal

CPET information:

1. 12 lead ECG (Resting and exertion)

2. Lung function: Spirometry and lung volume

flow loops

3. Oxygen consumption during exercise

4. VO2 max

5. Anaerobic threshold (Lactate threshold)

6. Metabolism during exercise (Fat vs.

carbohydrate burning)

7. Cardiac and respiratory function during

exercise Who might need a CPET?

•Patients scheduled for major surgery

•Patients taking part in a health check-up for

the diagnosis of heart and lung disease

•Patients in rehabilitation following a major

illness

•Healthy subjects assessing their fitness,

personal fitness goals and or weight loss

targets

•Athletes at all levels needing expert guidance

to titrate training programs

•Athletes looking to quantify fitness levels and

evaluate training effectiveness

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in Willmore, JA. and Costill, DL.(1994).Phsysiology of sport and exercise

METABOLISM: Muscle Fuel Sources

Important Questions

1. How is energy released?

2. What fuels sources exist in our body?

3. Where does ATP come from?

4. What pathways can we use to make ATP?

5. Why do we slow down?

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ATP or adenosine triphosphate is the energy currency used by

our body everyday to perform a number of tasks:

METABOLISM: Energy Release

• Maintain body temperature

• Repair damaged cells

• Digestion of food

• Mechanical work – movement

ATP↔ ADP + Energy

http://www.lactate.com/triathlon/lactate_triathlon_energy_basic.html

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Fact: Our muscles already contain ATP molecules

METABOLISM: Our need for Energy

Problem: There are not enough!

Physiology Principle: ATP Supply = ATP DemandEnergy

Result: Find other ways to provide our body with ATP

In order to maintain exercise we need to supply our

muscles with an adequate amount of ATP or energy.

Question: Where does the additional ATP come from?

METABOLISM: Sources of Energy

The chemical breakdown of

the fuel sources in our body:

a. Muscle Glycogen

b. Blood Glucose (Liver)

c. Fats (Adipose Tissue)

d. Proteins (Amino Acids)*

ATP ↔ ADP + Energy

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Characteristics of Human Muscle

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)

Important: two factors determine the amount of ATP

required to perform exercise and the types of fuel used:

METABOLISM: Sources of Energy

I. Exercise Intensity : rate of ATP production

II. Exercise Duration: amount of ATP production

ATP ↔ ADP + Energy

In the next section we will learn to categorise sporting events

using exercise intensity and duration to determine the energy

systems that are being used to provide our bodies with ATP.

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In Katch, VL. et al (2011). Essencials of Exercise Physiology.

ATP is able to be produced by more than one system/ pathway

METABOLISM: ATP Production

1. Anaerobic “O2 independent”

Does not require oxygen

2. Aerobic “O2 dependent”

Requires oxygen

O2

O2

A system can be categorised as either:

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Remember: these pathways generate energy without using O2

METABOLISM: Anaerobic Pathways

1. ATP-CP system

• ATP ‘reservoir’

• Immediate energy system

2. Anaerobic Glycolysis system

• Exclusively uses CHO

• Short-term “lactic acid” system

ATP is produced by these energy systems:

Remember: these pathways require O2 to generate energy

METABOLISM: Aerobic Pathways

3. Aerobic glycolytic (CHO) system

• Moderate- to high-intensity exercise

• Finite energy source (CHO →ATP)

4. Aerobic lipolytic (Fat) system

• Prolonged low-intensity exercise

• Unlimited energy source (Fat →ATP)

ATP is produced by these energy systems:

CHO

FAT

O2

AT

P

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Energy Systems

Energy SystemsMole of

ATP/minTime to Fatigue

Immediate: Phosphagen (Phosphocreatine

and ATP)4 5 to 10 sec

Short Term: Glycolysis

(Glycogen-Lactic Acid)2.5 1.0 to 1.6 min

Long Term: Aerobic system 1 Unlimited time


Anaerobic vs Aerobic

Energy Systems

• Anaerobic

– ATP-PCR : ≤ 10 sec.

– Glycolysis: < 3 minutes

• Aerobic

– Krebs cycle

– Electron Transport Chain

– ß-Oxidation

2 minutes +


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100%

% C

ap

aci

ty o

f E

ne

rgy S

yste

m

10 sec 30 sec 2 min 5 min +

Aerobic

Glycolysis

Phosphagen (ATP-PCR)

Energy Transfer Systems and Exercise

Aerobic and Anaerobic

ATP Production

Oxidative Phosphorylation

ATP-production

Fatty acids

Glycogen

Glucose

PCRATP

ATP-stores

Immediate

Glycolysis

Short-term

aerobic

Long-term

system

Substrate level phosphorylation TCA-Cycle

Amino acids

Anaerobic

Glycolysis

Aerobic

Glycolysis

ß-oxidation


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En

erg

y e

xpe

nd

itu

re (

J/k

g/m

in)

EFFECTS OF EXERCISE INTENSITY ONFUEL SELECTION DURING EXERCISE

1500

1200

900

600

300

Plasma glucose

Plasma FFA

IMTG

Muscle glycogen

25 65 85

Relative exercise intensity (% of VO2max)

Romijn et al. Am. J Phsyiol. Endocrin. Metab. 265: E380-E391, 1993.

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Comparison of Aerobic and Anaerobic ATP

production

Limiting Factors

Anaerobic

Glycolysis

Aerobic

Glycolysis

ATP/PC

R ß-oxidation

Velocity of supply + + + - - -

Rate of supply + + + - - -

Stores - + + + +

Efficiency ? - - + + +

Aerobic glucose degradation yields 18-19 more ATP

than anaerobic, but velocity and rate are lower

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The contribution of these systems to energy production will depend on the

event type:

49.6%

44.1%

6.3%

60%50%

35%

40%50%

65%

92%

8%

50%

50%

ATP CP Anaerobic

Glycolytic

Aerobic

Glycolytic

Aerobic

Lipolytic

6 sec 30 sec 60 sec 2 min 1 hour 4 hours

Peak Performance, Hawley & Burke (1998)

• Sporting events can be classified into 4 main

categories listed below:

1. Power Events

2. Speed Events

3. Endurance Events

4. Ultra-Endurance Events

ENERGY SYSTEMS: Athletic Events

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The body has 4 distinct systems it can use to supplyenergy for these different types of events:

Event Energy System

ENERGY SYSTEMS: Pathwaysc

1. Power (Jump)

2. Speed (Sprint)

3. Endurance (Run)

4. Ultra-Endurance

ATP-CP system (phosphagen)

Anaerobic system (O2 independent)

Aerobic glycolytic (CHO) system

Aerobic lipolytic (Fat) system

Event Type: Maximal strength & speed

Event Duration: 0 - 6 sec (Dominant System)

Energy Sources

1. ATP ↔ ADP + Pi + H+

2. CP + ADP + H+ ↔ ATP + Cr

Availability: Immediate- stored in muscle

Anaerobic Power: Large

Anaerobic Capacity: Small

ENERGY SYSTEMS: ATP-CP (Phosphagen)

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Event Type: Maximal speed or high-intensity efforts

Event Duration: 6 - 60 sec (Dominant System)

Energy Sources

Muscle Glycogen ↔ 2 ATP + 2 Lactate + 2H+

Availability: Rapid- via glycogen breakdown (glycolysis)

Anaerobic Power: Moderate

Anaerobic Capacity: Larger than ATP-CP

ENERGY SYSTEMS: Anaerobic (O2 independent)

Modified from http://www.lactate.com/triathlon/lactate_triathlon_energy_basic.html

Aerobic

system

Lactate

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Oxidative phosphorylation

Event Type: Moderate and High-intensity exercise

Event Duration: 2 min – 1.5 hours (Dominant System)

Energy Sources

Carbohydrates + O2 ↔ 38 ATP + by-products

Availability: Fast- via breakdown CHO

Aerobic Power: Large

Aerobic Capacity: Large but limited

ENERGY SYSTEMS: Aerobic Glycolytic (CHO)

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Event Type: Low-intensity exercise

Event Duration: 4 hours+ (Dominant System)

Energy Sources

Fats + O2 ↔ 456 ATP + by-products

Availability: Slow- via fat breakdown (lipolysis)

Aerobic Power: Low

Aerobic Capacity: Unlimited

ENERGY SYSTEMS: Aerobic Lipolytic (Fat)

Lactic Acid

Acetyl-CoA Lactate

Glucose 6-P G-3-P Pyruvate

Regeneration 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+ can’t pass H+ to mitochondria, H+ is passed to pyruvate to form lactate.

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Pyruvate:Lactate

Oxygen Uptake and HR

Exercise Domains

2

0 12Time (minutes)

24

4

2

150

Work Rate (Watts)

INCREMENTAL CONSTANT LOAD

Moderate

Heavy

TLac Wa

300

VO

2(l/m

in)

SevereModerate

Heavy

Severe

0

4

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Lactate/Lactic Acid

• A 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.

Exercise Intensity Domains

• Moderate Exercise:

– All work rates below LT

• Heavy 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

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Lactate and Exercise Domains

0

6

12

0 12 24

Time (minutes)

Heavy

Moderate

Severe

Lactate Threshold

• Intensity 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.

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• Anaerobic threshold or AT

– first used in 1964

– based on ↑ blood La- being associated with hypoxia

• Should not be used

• Onset of blood lactate accumulation

– maximal steady state blood lactate concentration

• Can vary between 3 to 7 mmol/L

• Usually assumed to be around 4 mmol/L

Lactate Threshold

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Lactate Threshold

• LT as a % of VO2max or workload

– Sedentary individual→ 40-60% VO2max

– Endurance-trained→ > 70% VO2max

• LT: Maximal lactate at Steady State exercise

– Max intensity SS-exercise can be maintained

– Prescribe intensity as % of LT

Blood Lactate as a Function of Training

Blo

od L

acta

te (

mM

)

Percent of VO2max

25 50 75 100

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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)

Redox

Potential

Mitochon

Capacity for

Pyruvate

Exceeded

La-

Production

Blood

Catechols

Lactate

Threshold

Reduced

Removal of

Lactate

Low

Muscle O2

Accelerated

Glycolysis

Recruitment

of Type II

Fibers

Mechanisms of La production

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Lactate is Critical to Cellular Function

• Does not cause acidosis related to fatigue

– pH in body too high for Lactic Acid to be formed

• Assists in regenerating NAD+ (oxidizing power)

– No NAD+, no glycolysis, no ATP

• Removes H+ when it leaves cell: proton consumer

– Helps maintain pH in muscle

• Can be converted to glucose/glycogen in liver via Cori cycle

The relative strength of the aerobic and anaerobic

systems determines substrate utilization for ATP

replacement.

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Mader model - Pyruvate/lactate formation at a given effort level depends

on three variables :

VO2 max - this is aerobic capacity or the maximum rate of energy production

by the aerobic system. VO2 max is usually estimated by a device attached to the

mouth and nose of an athlete. The device measures oxygen uptake by athletes

as they complete a progressive exercise test to exhaustion.

VO2 steady state - this is the amount of aerobic energy that is being used

during a submaximal steady state exercise. It is usually measured using the

same instruments as for VO2 max.

VLamax - this is anaerobic capacity or the maximum rate of energy production

by the glycolytic system. It is sometimes designated by the term Plamax or

maximum production of lactate. In reality this is the maximum rate of

production of pyruvate and lactate but since lactate is what is measured “La”

has been used for this term.

The theory states that VLa (the production of lactate) at

any steady state level is a function of VO2 max, VO2 at

that level and VLamax. In http://www.lactate.com

Estimate of lactate production in the muscle fiber itself

http://www.lactate.com

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Heath et al. (1981). Journal of Applied Physiology. 51 (3) 634-640

Intensity Principle: Lactate production increases as intensity

increases (the levels will be variable within each individual athlete).

Aerobic Capacity Principle: as aerobic capacity increases, the

utilization of the anaerobic system will decrease at every intensity

level in a steady state situation.

Anaerobic Capacity Principle: as anaerobic capacity increases ,the

utilization of the aerobic system will decrease at every intensity

level.

The anaerobic system acts as a Gate Keeper for the

Aerobic System. It determines how much it can get

use.

Adapted from http://www.lactate.com

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Ventilatory 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.


• 3 methods used in research:

– Minute ventilation vs VO2, Work or HR

– V-slope (VO2 & VCO2)

– Ventilatory equivalents (VE/VO2 & VE/VCO2)

• Relation of VT & LT

– highly related (r = .93)

– 30 second difference between thresholds

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Muscle RBC Lung

H+ + HCO3- H2CO3 H2O + CO2


• During incremental exercise:

– Increased acidosis (H+ concentration)

– Buffered by bicarbonate (HCO3-)

Marked by increased ventilation

Hyperventilation


1000

2000

3000

4000

5000

6000

2000 2500 3000 3500 4000 4500

VO 2 (ml/min)

AT

By V Slope Method

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80 100 120 140 160 180

Heart Rate

0

50

100

150

200

VE

(L/

min

)

By Minute Ventilation Method

Respiratory Exchange Ratio/Quotient

• Respiratory Exchange Ratio (RER): CO2 expired/O2

consumed

• Respiratory Quotient (RQ): CO2 produced/O2

consumed at cellular level

• RQ indicates type of substrate (fat vs. carbohydrate) being metabolized:

– 0.7 when fatty acids are main source of energy.

– 1.0 when CHO are primary energy source.

• Can exceed 1.0 during heavy non-steady state, maximal exercise due to increased respiratory and metabolic CO2.

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Oxygen Deficit and Debt

• Oxygen deficit: difference between the total oxygen used during exercise and the total that would have been used if it had achieved steady state immediately

• Excess Post-Exercise O2 Consumption (EPOC) or O2 debt: increased rate of O2 used during recovery period. The extra oxygen is used in theprocesses that restore the body to a resting stateand adapt it to the exercise just performed.

Oxygen Deficit and Debt

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EPOC or Recovery VO2

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 re-conversion of lactate to glycogen.

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Energy expenditure: is the energy expended by individuals

engaging in physical activity and is often expressed in kilocalories.

Activities can be categorized as light, moderate or heavy by deter-

mining the energy cost.

Quantification of Energy Expenditure Energy expended is

computed from the amount of oxygen consumed. Units used to

quantify energy expenditure are:

A Kilocalorie is a measure expressing the energy value of food. It is the amount of

heat necessary to raise 1 kilogram (kg) of water 1C. A kilocalorie (kcal) can be

expressed in oxygen equivalents. Five kilocalories equal approximately 1 liter of

oxygen consumed (5 kcal 1 liter O2).

A MET is defined as the oxygen consumed (milliliters) per kilogram of body weight

per minute (mL/kg). It is equal to approximately 3.5 mL/kg per minute


(RER + 4) x (L/O2 consumed per minute) = kcal/minute

• Example:

– RER determined from gas analysis =0.75

– 4.0 + 0.75 = 4.75

– L of O2 per minute = 3 liters

– 4.75 x 3 = 14.25 kcal/min

– If exercised for 30 minutes = 427.5 kcals

Estimating Energy Expenditure

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Estimating Energy Expenditure

From RER: (RER + 4) x (L/O2 per minute) = kcal/minute

– RER = 0.75

– 4.0 + 0.75 = 4.75

– L of O2 per minute = 3 liters

– 4.75 x 3 = 14.25 kcal/min

From VO2: 1 L/min of O2 is ~ 5 kcal/L

– VO2 (L/min) = 3

– 3 * 5 kcal/L = 15 kcal/min

3.+aerobic+capaciy+and+endurance (1)

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