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Prediction of Maximal Oxygen Consumption

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Assessing Cardiorespiratory
Endurance
A Fitness Indicator
Determination of Fitness Level
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Everyone possesses some degree of
cardiorespiratory endurance (CRE)
CRE=a health associated component
that relates to the ability of circulatory
and respiratory systems to supply fuel
during sustained physical activity and to
eliminate fatigue products after
supplying fuel.
VO2 max
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VO2 max is the most commonly used
index to assess CRE
Definition - The largest amount of
oxygen that an individual can utilize
during strenuous exercise to complete
exhaustion
Has become the accepted measure of
CRE
AEROBIC GLYCOLYSIS AND THE
ELECTRON TRANSPORT CHAIN
KREBS
CYCLE
METABOLISM OF FAT
OXIDATIVE PHOSPHORYLATION
VO2 max
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Units
– liters/minute or ml/minute (absolute)
– ml/kg/min (relative to body weight)
– ml/kg of FFM/min (relative to FFM)
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Range 15 (sedentary with disease) to
75 (young endurance runner) ml/kg/min
Women about 10-20% lower than men
Methods of Determining VO2
max
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Submaximally
Maximally
GXT
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Graded Exercise Testing - GXT
(incremental increases in workload)
General Guidelines
– measure the subject’s HR and BP and
RPE at regular intervals (near the end of
each stage [HR, BP, RPE] or every minute
[HR])
– if HR does not reach steady state during
the stage extend stage 1 minute
GXT
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General Guidelines
– All testing begins with a 2-3 min warm-up
– Cool- down at a low intensity for at least 4
minutes - continue measuring HR, BP and
RPE
– increase intensity in .5-2 MET increments
– closely observe subject for
contraindications
Submaximal Assumptions
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1. A steady-state HR is obtained for
each exercise work rate
2. A maximal HR for a given age is
uniform (220-age)
Assumptions
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3. Mechanical efficiency (ie. VO2 at a
given work rate) is the same for
everyone.
– This may not be true and it has been
suggested that submaximal exercise
testing underestimates VO2max in the
untrained and overestimates in the trained
Submaximal Assumptions
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4. There is a linear relationship
between HR and Workload
5. HR will vary depending on fitness
level between subjects at any given
workload
Age vs. HR
HR (beats/min)
HR vs. Age
240
190
HR - max
140
90
10 20 30 40 50 60 70 80
Age (years)
Submaximal Protocols
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Oxygen consumption for any given WL
does not vary between subjects
The slope of the line is about the same
for any two given subjects
The rate of increase in O2 consumption
with increasing WL does not vary
between subjects
EXERCISE INTENSITY AND OXYGEN
UPTAKE
Submax Protocols
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HR does vary between subjects
rate of increase in HR depends on
fitness level
The more fit you are the lower your HR
at any given WL
An untrained person will reach their HR
max at a lower WL vs. a trained person
of the same age.
HEART RATE AND INTENSITY
HEART RATE AND TRAINING
190
170
150
130
110
90
untrn
00
21
00
18
00
15
00
12
0
90
0
60
0
trn
30
HR (bpm)
HR vs. Workload
Workload (kgm/min
.
HEART RATE, VO2, AND INCREASING
WORK
HR vs. WL and VO2
HR (bpm)
250
200
150
Hr
100
50
0
150
0.6
600
1.5
1050
2.4
1500
3.5
1950
4.6
VO2 (l/min) and Workoad
(kgm/min)
Submaximal Protocols
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1.
2.
3.
4.
5.
YMCA - bike
Astrand Rhyming – bike
ACSM - bike
Bruce Protocol - treadmill
McCardles Step Test
YMCA
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Multi-stage protocol
3-4 consecutive 3 minute stages
HR between 110-150 bpm (the HR
range at which the relationship between
VO2 and WL is most linear)
YMCA Procedures
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1. Adjust seat height (legs nearly
straight when extended - 5Вє bend)
2. Measure pre-exercise BP and HR
with subject seated on bike
3. Pedal at 50 rpm (if using a
metronome - 100x/minute)
4. Warm-up, zero resistance for 2-3
minute
YMCA Protocol
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5. Stage 1
– .5 kp for 3 minutes
– at every stage measure BP at 2.0 min
(more often if hypertensive)
– at every stage measure HR during last half
of minutes 2 and 3
– if HR at 2 and 3 minutes differ by more
than 6 bpm extend the stage for 1 min
YMCA Protocol
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6. Stage 2
– Workload in this stage and successive
stages depends on HR during stage 1 (p
75 guidelines)
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7. Continue test until HR recorded at
two successive WL are between 110
and 150 bpm (for many this occurs
during 2nd and 3rd WL)
YMCA Protocol
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8. Note that if HR is greater than 110 at
end of 1st stage then only one more
stage is necessary
9. At completion of test reduce
resistance to .5kp and allow subject to
pedal for at least 4 minutes or until HR
falls below 100 bpm and BP stabilizes.
YMCA Protocol
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10. The HR measured during the last
minute of each stage is plotted against
workload.
11. The line generated from the plotted
points is extrapolated to the agepredicted HR max
12. A perpendicular line is dropped to
the x-axis to estimate the work rate this
person would achieve if taken to max.
200
HR
150
100
Hr
50
0
150
0.6
450
1.2
750 1050 1350 1650
1.8 2.4 3.2 3.8
VO2 (l/min) and Workload
(kgm/min)
ACSM Bike Test
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1. 2-3 minute warm-up
2. Take HR twice during each stage (3
minute stages) and RPE/BP once
(similar to YMCA)
3. If HRs are greater than 110, steady
state should be reached (HRs within
6bpm) before increasing the workload
ACSM
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Protocol
Stage 1
Stage 2
Stage 3
Stage 4
A
150
300
450
600
B
150
300
600
900
C (kgm/min)
300
600
900
1200
ACSM
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Protocol Selection
BW
Very Active
(kg)
No
Yes
<73
A
A
74-90 A
B
>91
B
C
– *very active is defined as aerobic exercise
20 minutes, 3 days/week
ACSM
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5. Terminate test when HR reaches
85% of age-predicted max HR or 70%
of HR reserve
6. Recovery at workload equal to the 1st
stage or less for at least 4 minutes with
HR, BP, and RPE monitored.
ACSM
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Plot HRs from last two stages to
determine VO2max much like YMCA.
Astrand Rhyming
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Single-stage test (VO2 max is
determined using 1 submaximal data
point-HR)
Duration of test is 6 minutes
Astrand Rhyming
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1. Adjust seat height (legs nearly
straight when extended - 5Вє bend)
2. Measure pre-exercise BP and HR
with subject seated on bike
3. Pedal at 50 rpm (if using a
metronome - 100x/minute)
4. Warm-up, zero resistance for 2-3
minute
Astrand Rhyming
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5. Pedal rate is 50 rpm
6. Determine Workload
– unconditioned males - 300 or 600 kgm/min
– conditioned males - 600 or 900 kgm/min
– unconditioned females - 300-450 kgm/min
– conditioned females - 450 or 600 kgm/min
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7. 6 minute test
Astrand Rhyming
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8. At end of 2nd minute of pedaling
take HR (BP at 1.25-1.5 min)
– want the HR to be between 125-170bpm
– if less than 125 increase resistance by 1 kp
for men and 1/2 kp for women
– if greater than 170 bpm decrease
resistance by 1 kp
– continue to monitor HR every minute until
HR exceeds 125
Astrand Rhyming
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9. At the end of the 5th and 6th minute
take HR and average the two values
(make sure values are within +6bpm to
assure a steady state HR was obtained)
10. BP at 4:30 and 5:30
11. Reduce resistance and cool-down
for 4 minutes.
Astrand Rhyming
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10. Determine VO2 from nomogram (p.
73 guidelines, p.69 Heyward)
11. Age-correction factor (p. 74
guidelines, p.72 heyward)
12. Convert to relative value
Treadmill Tests
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Bruce Protocol
Balke
Ellestad
Others……….
Treadmill Protocols
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Bruce and Ellestad
– larger increments
– use on younger and/or more physically
active
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Balke-Ware
– smaller increments (1MET/stage or lower)
– use on older, deconditioned, and/or
diseased subjects
Treadmill Protocol
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Single-stage (using one data point)
even though we may have more than
one stage
May need to have a long
accustomization period and explanation
of procedures before beginning
Bruce Treadmill Protocol
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1. Measure resting BP and HR while
standing on the belt of the treadmill
2. Ask subject to straddle the belt while
starting treadmill at 1.7 mph and 0% grade
3. Ask subject to begin walking and when
comfortable release handrails
4. This is a warm-up and should continue
until subject is comfortable
Bruce Treadmill Protocol
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5. Stage 1
– Increase grade to 10%
– 3 minutes long
– Measure HR at end of each minute and BP
at end of each stage
Bruce Treadmill Protocol
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6. The objective is to reach a steady
state HR between 115 and 155 bpm
(usually occurs during the first 6
minutes of exercise or by the end of the
2nd stage) – Page 98 guidelines
7. Once subject reaches proper HR
terminate the test at the end of that
stage
Bruce Treadmill Protocol
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8. Reduce treadmill speed to 1.7mph
and 5% grade and cool-down for 4
minutes.
9. VO2 is estimated from the last
minute of a fully completed stage
Treadmill Protocol
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10. Calculate VO2 from the gender specific
equations
Males
– VO2=SMVO2 [(HRmax-61)/(HRSM-61)]
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Females
– VO2=SMVO2[(HRmax-72)/(HRSM-72)]
– SMVO2 = submaximal VO2 from table or ACSM
equations
– HRSM = submax HR from test
Modified Bruce Protocol
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Start at 1.7 mph, 0% grade or at 1.7
mph and 5% grade (used on diseased
and elderly populations)
Treadmill Protocol
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Protocols should be individualized
Test time should ideally be 8-12min
Increments of 10-15 W/min or 1-3%/min
grade can be used for the elderly
McCardle’s Step Test
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Bench ht. = 41.25 cm
Step Rate = 24 step/min (metronome =
96) for men and 22 step/min
(metronome=88) for women
3 minutes of stepping
Record HR from the first 15seconds
after the stepping has stopped
McCardle
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Men
– VO2 = 111.33 - (0.42 x HRrec)
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Women
– VO2 = 65.81 - (0.1847 x HRrec)
– value is ml/kg/min
Maximal Testing
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Assumption: The subject was highly
motivated and gave a maximal effort.
Max Testing
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Laboratory Tests
1. Open Circuit Indirect Calorimetry
2. Cycle
3. Treadmill (Bruce)
Maximal Protocols
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Field Tests
4. 12 minute run
5. 1.5 mile run
6. Rockport Walking Test
Measuring Energy Costs of
Exercise
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Direct calorimetry—measures the
body's heat production to calculate
energy expenditure.
Indirect calorimetry—calculates
energy expenditure from the respiratory
exchange ratio (RER) of CO2 and O2.
A CALORIMETRIC CHAMBER
Open Circuit Indirect
Calorimetry (Gas Analysis)
% O 2 in the A ir= 20.93 %
(for s im p lic ity 21 % )
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V I= V o lu m e o f A ir
Inha led b y the subject
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Fo r exa m p le 100L /m in
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G as
A na lys is
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 V O 2 E = V o lum e o f O 2 exp ired= 16 L /m in
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V O 2m ax = 21L/m in – 16 L /m in
= 5L/m in
V E -V o lum e o f A ir
E xp ired b y S ubject
   (let’s assum e fo r
sim p lic ity = V I
= 100 L/m in)
Respiratory Exchange Ratio
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The ratio between CO2 released (VCO2)
and oxygen consumed (VO2)
RER = VCO2/VO2
The RER value at rest is usually 0.78 to
0.80
RER
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Value ranges from .7-1.0
0.7 mainly uses fats as an energy
source
1.0 mainly uses carbohydrates as an
energy source
Can exceed 1.0 during heavy nonsteady state, maximal exercise, or when
nervous due to hyperventilation
(increased CO2)
KCALS
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(RER + 4) x (Liters of O2 consumed per
minute) = kcal/minute
For example:
– RER determined from gas analysis = .75
– 4 + .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
Cycle to Max
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15 W/min protocol
VO2males =10.51 (power in W) + 6.35
(BW in kg) - 10.49 (age in y) + 519.3
VO2females =9.39 (power in W) + 7.7 (BW
in kg) - 5.88 (age in y) + 136.7
values are in ml/min - divide by BW in
kg
Treadmill to Max (Bruce)
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VO2 = 14.8 - 1.379 (time in min) + 0.451
(time2) - 0.012 (time3)
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While holding handrail
VO2 = 2.282 (time in min) + 8.545
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Population-specific Equations
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P. 61 Heyward
Active vs. Sedentary, Gender specific,
Cardiac patients
12 minute run
80
60
40
20
0
Distance
1.
9
1.
7
1.
5
VO2
1.
3
1.
1
VO2
VO2
12 minute run
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The further you can run in 12 minutes
the higher your VO2max
1.5 mile run/Rockport Walking
80
VO2
60
40
VO2
20
0
6
8
10
12
time
14
16
18
1.5 Mile Run/1 Mile Walk
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The faster you can run 1.5 miles or walk
1 mile the higher your VO2max
Field Tests
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12 min run
– VO2 = 3.126 (meters in 12 min) - 11.3
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1.5 mile run
– VO2 = 3.5 + 483/(time in minutes)
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Rockport Walking Test (1 mile walk)
– VO2 = 132.853 - 0.1692 (BW in kg) 0.3877 (age in y) + 6.315 (gender) - 3.2649
(time in min) - 0.1565 (HR)
– 0 for female; 1 for male; HR at end of walk
Normal Responses to GXT
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1. Systolic BP increases in direct
proportion to increasing WL
2. HR increases linearly with WL
3. Diastolic BP changes very little
4. Shortened QT Interval
5. Reduced R-wave amplitude
6. Positive upslope of ST segment
Abnormal responses to GXT
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1. ST segment depression
2. Increased R-wave amplitude
3. V-tach
4. Multiform PVC’s
5. Failure of HR to rise with WL
6. Failure of systolic to rise
7. Systolic and diastolic greater than 250 or
120
Test Termination
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1. Have reached a pre-determined
endpoint
Absolute
1. Suspicion of myocardial infarction
2. Moderate to severe angina
3. Drop in Systolic BP with increasing
Workload (>20)
Absolute
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4. Arrhythmias
5. Pale or cold and clammy skin
6. Severe shortness of breath
7. Dizzy, blurred vision, or confusion
8. Patient requests stop
9. V-tach or multiform PVC’s
10. ST segment depression
Absolute
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11. Excessive rise in BP (systolic >250;
diastolic >120)
12. Failure of HR to increase
Relative
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1.
2.
3.
4.
5.
6.
7.
ECG changes from baseline
Chest pain that is increasing
Wheezing
Leg cramps
High Systolic/Diastolic
Less serious arrhythmias
Less severe shortness of breath
Advantages of Submaximal
Testing
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1. Safer
2. Controlled pace (motivation not a
factor)
3. Not population specific (no pacing
advantage)
4. Quick assessment
5. Cost effective
Advantages of Submaximal
Testing
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6. Don’t need highly trained personnel
7. Can do mass testing
8. No physician supervision required (if
symptom and disease free)
Disadvantages of Submaximal
Testing
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1. VO2 max is not directly measured
(error rate of 10-20%)
2. Don’t get a measure of true maximal
HR
– estimates of max HR using 220-age can
vary by +15 bpm for individuals of the
same age
Advantages and Disadvantages of
a Maximal Test
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Advantages
1. More accurate
Disadvantages
1. Motivation is a factor
2. More risk involved
3. Time
4. Cost of equipment (if using metabolic
cart)
Walking/Running vs.
Cycling/Stepping
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Walking/Running are the most natural
forms of locomotion (most Americans
are unaccustomed to cycling
In general, subjects reach higher
VO2max values during treadmill tests
Treadmill are more expensive than
cycles
Treadmill is less portable
Walking/Running vs.
Cycling/Stepping
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Body weight has a much smaller effect
on cycle ergometry versus treadmills
Treadmill more dangerous (greater risk
of a fall
Measurement of HR is more difficult on
a treadmill and while stepping
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