Assessing Cardiorespiratory Endurance

A Fitness Indicator

Determination of Fitness Level

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

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

Units– liters/minute or ml/minute (absolute)– ml/kg/min (relative to body weight)– ml/kg of FFM/min (relative to FFM)

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 Submaximally Maximally

GXT

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

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

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

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

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. HRHR vs. Age

90

140

190

240

10 20 30 40 50 60 70 80

Age (years)

HR

(bea

ts/m

in)

HR - max

Submaximal Protocols

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

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

HR vs. Workload

90110130150170190

Workload (kgm/min

HR (b

pm) untrn

trn

HEART RATE, VO2, AND INCREASING WORK

.

HR vs. WL and VO2

0

50

100

150

200

250

1500.6

6001.5

10502.4

15003.5

19504.6

VO2 (l/min) and Workoad (kgm/min)

HR

(b

pm

)

Hr

Submaximal Protocols

1. YMCA - bike 2. Astrand Rhyming – bike 3. ACSM - bike 4. Bruce Protocol - treadmill 5. McCardles Step Test

YMCA

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

1. Adjust seat height (legs nearly straight when extended - 5º 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

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

6. Stage 2 – Workload in this stage and successive

stages depends on HR during stage 1 (p 75 guidelines)

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

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

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 age-predicted 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.

0

50

100

150

200

1500.6

4501.2

7501.8

10502.4

13503.2

16503.8

VO2 (l/min) and Workload (kgm/min)

HR Hr

ACSM Bike Test

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

Protocol A B C (kgm/min) Stage 1 150 150 300 Stage 2 300 300 600 Stage 3 450 600 900 Stage 4 600 900 1200

ACSM

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

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

Plot HRs from last two stages to determine VO2max much like YMCA.

Astrand Rhyming

Single-stage test (VO2 max is determined using 1 submaximal data point-HR)

Duration of test is 6 minutes

Astrand Rhyming

1. Adjust seat height (legs nearly straight when extended - 5º 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

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

7. 6 minute test

Astrand Rhyming

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

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

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

Bruce Protocol Balke Ellestad Others……….

Treadmill Protocols

Bruce and Ellestad– larger increments– use on younger and/or more physically

active Balke-Ware

– smaller increments (1MET/stage or lower)– use on older, deconditioned, and/or

diseased subjects

Treadmill Protocol

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

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

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

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

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

10. Calculate VO2 from the gender specific equations

Males– VO2=SMVO2 [(HRmax-61)/(HRSM-61)]

Females– VO2=SMVO2[(HRmax-72)/(HRSM-72)]

– SMVO2 = submaximal VO2 from table or ACSM equations

– HRSM = submax HR from test

Modified Bruce Protocol

Start at 1.7 mph, 0% grade or at 1.7 mph and 5% grade (used on diseased and elderly populations)

Treadmill Protocol

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

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

Men– VO2 = 111.33 - (0.42 x HRrec)

Women– VO2 = 65.81 - (0.1847 x HRrec)

– value is ml/kg/min

Maximal Testing

Assumption: The subject was highly motivated and gave a maximal effort.

Max Testing

Laboratory Tests 1. Open Circuit Indirect Calorimetry 2. Cycle 3. Treadmill (Bruce)

Maximal Protocols

Field Tests 4. 12 minute run 5. 1.5 mile run 6. Rockport Walking Test

Measuring Energy Costs of Exercise

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)

% O2 in the Air=20.93% VI=Volume of Air(for simplicity 21%) Inhaled by the subject

For example 100L/min

GasAnalysis

VE-Volume of AirExpired by Subject

VO2E=Volume of O2 expired=16L/min (let’s assume for simplicity = VI =100L/min)

VO2max = 21L/min – 16 L/min= 5L/min

Respiratory Exchange Ratio

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

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 non-steady

state, maximal exercise, or when nervous due to hyperventilation (increased CO2)

KCALS

(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

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)

VO2 = 14.8 - 1.379 (time in min) + 0.451 (time2) - 0.012 (time3)

While holding handrail VO2 = 2.282 (time in min) + 8.545

Population-specific Equations

P. 61 Heyward Active vs. Sedentary, Gender specific,

Cardiac patients

12 minute run

VO2

020406080

Distance

VO2 VO2

12 minute run

The further you can run in 12 minutes the higher your VO2max

1.5 mile run/Rockport Walking

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time

VO2 VO2

1.5 Mile Run/1 Mile Walk

The faster you can run 1.5 miles or walk 1 mile the higher your VO2max

Field Tests

12 min run– VO2 = 3.126 (meters in 12 min) - 11.3

1.5 mile run– VO2 = 3.5 + 483/(time in minutes)

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

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

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

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

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

11. Excessive rise in BP (systolic >250; diastolic >120)

12. Failure of HR to increase

Relative

1. ECG changes from baseline 2. Chest pain that is increasing 3. Wheezing 4. Leg cramps 5. High Systolic/Diastolic 6. Less serious arrhythmias 7. Less severe shortness of breath

Advantages of Submaximal Testing

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

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

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 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 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 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