Chapter 8

Cardiorespiratory Fitness

Cardiorespiratory Endurance

• Is considered health-related because:– Low levels are associated with an increase

risk of premature death, specifically from cardiovascular disease.

– High levels are associated with many health benefits.

• Lower blood pressure, body weight/fat, better control of blood sugar, etc.

Aerobic and Anaerobic• “Aerobic” means “with air”, “using oxygen”.

– The term aerobic relates to the energy processes that occur in the presence of adequate oxygen.

– “Aerobic Fitness” is the ability of the heart and lungs to provide the oxygen needs of the body (muscular system) over a sustained period of time.

– Aerobic Fitness may be limited by:• The ability of the lungs to intake O2 and transport to the blood• The ability of the heart to pump oxygenated blood to the

tissues, the ability of the blood vessels to carry the blood, or the ability of the blood to completely saturate with oxygen.

• The ability of the muscles to extract oxygen and to utilize it.

Anaerobic• “Anaerobic” refers to:

– an inadequate supply of oxygen to meet the demands of physical work; the body starts accumulating lactic acid, which is unable to reduce without adequate oxygen. In other words, because there is not enough O2 present, pyruvate is not allowed to enter into Krebs cycle in the cell’s mitochondria. Due to the lack of ample O2, pyruvate converts to Lactic acid, and accumulates in the cell.

• “Anaerobic threshold” refers to:– the point when oxygen availability is not sufficient to meet the demands

of the workload. The AT is the point at which blood lactate concentrations start to rise above resting values.

Oxygen Consumption• The most accepted index of work capacity is maximal oxygen consumption

(VO2max). (“V”= volume of oxygen used per minute, “O2”=oxygen, and “max”=maximal exercise conditions).

• VO2max represents the maximal rate of delivery of oxygen from the inspired air to the working tissues (skeletal muscle). In other words, VO2max is the greatest rate at which oxygen can be consumed during exercise or the maximal rate at which oxygen can be taken up, distributed, and used by the body during physical activity.

– Remember, “Uptake, Distribution, and Utilization.”• Physiologically, VO2max is the product of maximal cardiac output and maximal

(a-v O2) difference. This is the amount of O2 extracted from the blood.• Exercise training can significantly improve the oxygen transport system and

increase VO2 max by increasing both the maximal cardiac output and the maximal (a-v O2) difference.

– These improvements are one or a combination of improvements in the systems of respiration, cardiac function, central circulation, peripheral circulation, and skeletal muscle metabolism.

• The extent of improvement is determined, in part, by the net training work rate performed, and thus, depends on the frequency, intensity, and duration of each exercise session. The initial level of fitness also dictates the amount of fitness improvements (The lower the level of initial fitness, the greater possible gains.)

Maximal Oxygen Uptake (VO2max)

• Defined as the greatest rate at which oxygen can be consumed during exercise.

• Typically expressed in milliliters of oxygen consumed per kilogram of body weight per minute (ml.kg-1.min-1).

• Laboratory criteria for achieving a true VO2max:– Oxygen consumption plateaus during last minutes– RER increases to 1.15 or higher

– HR within 10 bpm of age-predicted HRmax

– Blood lactate levels rise above 8 mmol/liter

MEASUREMENT OF VO2MAX • The measurement of max VO2 is a

measurement of aerobic or cardio-respiratory fitness.

• Direct measurement of oxygen uptake during max exercise is considered the best measure of heart and lung endurance.

• However, direct laboratory measurement is expensive and time consuming, requires highly trained personnel, and therefore is not practical for most testing situations.

MEASUREMENT OF VO2MAX• Therefore, various formulas and tests

have been developed as substitutes.• They include:

– Non-exercise test VO2max prediction equations

– Field tests of cardio-respiratory endurance– Sub-maximal laboratory tests– Maximal laboratory tests.

Considerations prior to testing…

• When conducting a bicycle or treadmill test, the tester should include heart rate, blood pressure, and ECG monitoring on all high risk individuals.

• The test can then be used for determination of both cardio-respiratory fitness and potential health problems such as high blood pressure and heart disease (as dx by a physician).

• Although blood pressure and ECG monitoring is not necessary when testing apparently healthy subjects, some testing facilities do it as an extra precaution.

Resting Blood Pressure

• Blood pressure is the force of blood against the walls of the arteries and veins created by the heart as it pumps blood to every part of the body.

• Hypertension is a condition in which the blood pressure is chronically elevated above optimal levels (See p. 8 in packet).– Diastolic BP of > 90 mm Hg or systolic BP of

>140 mm Hg on at least two occasions.

Here's a look at the four blood pressure categories and what they mean for you.

Top number (systolic)

  Bottom number (diastolic)

Your category

What to do*

Below 120

and Below 80 Normal blood pressure

Maintain or adopt a healthy lifestyle.

120-139 or 80-89 Prehypertension

Maintain or adopt a healthy lifestyle.

140-159 or 90-99 Stage 1 hypertension

Maintain or adopt a healthy lifestyle. If blood pressure goal isn't reached in about 6 months, take one or more medications.

160 or more

or 100 or more Stage 2 hypertension

Maintain or adopt a healthy lifestyle. Take more than one medication.

*Note: These recommendations address high blood pressure as a single health condition. If you also have heart disease, diabetes, chronic kidney disease or certain other conditions, you'll need to treat your blood pressure more aggressively.

Source: Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure, 2003. Numbers are expressed in millimeters of mercury (mm Hg).

Adopting healthy lifestyle habits goes far in controlling and reducing high blood pressure. Here's how five basic changes to your lifestyle can reduce your systolic blood pressure — the first number in a blood pressure reading.

What to doHow to do it Reduction in systolic

blood pressure*

Maintain normal body weight (body mass index 18.5-24.9)

Eat a healthy diet; get plenty of exercise 5-20 mm Hg per about 22-pound weight loss

Adopt DASH eating plan Eat lots of fruits, vegetables and low-fat dairy products; cut back on fat

8-14 mm Hg

Reduce dietary sodium Limit sodium consumption to 1,500 mg to 2,400 mg a day; in general, less is better.

2-8 mm Hg

Get regular physical activity Engage in exercise that increases your heart and breathing rates for at least 30 minutes most days of the week

4-9 mm Hg

Drink alcohol only in moderation Limit alcohol to 2 drinks a day for men and 1 drink a day for women 2.5-4 mm Hg

*The effects of adopting these modifications in your lifestyle can vary by individual. To reduce your overall risk of cardiovascular disease, don't smoke.

•DASH is Dietary Approaches to Stop Hypertension. •mm Hg is millimeters of mercury •mg is milligrams Source: Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure, 2003.

• To take blood pressure, a sphygmomanometer and a stethoscope are needed.

• Several blood pressure readings by different observers, or on different occasions by the same observer, are recommended.

• See page 9 in packet and p. 32-38 ACSM for guidelines to take blood pressures.

Heart Rate

• The RHR can be obtained through auscultation (stethoscope bell), palpation (feeling with fingertips), or ECG recordings.

• With palpation, use the radial artery at rest, and the carotid artery during exercise.

• The RHR fluctuates widely; measure upon awakening three mornings in a row, and average.

Heart Rate• Heart rate refers to the number of times the heart contracts in 1 min.

• True resting heart rate should be taken upon awakening, and averaged from measurements taken on at least 3 separate mornings.

• Sites of palpation: best determined during rest at the radial artery. During exercise, it is easier to feel the carotid artery, but remember to use caution!!

• Resting heart rate can be affected by medications, level of conditioning, stress, season of the year, gender, and smoking.

– See p. 38-40 ACSM• Max heart rate is the maximum

number of times per minute the heart could beat.

– Estimated max beats equation is 220-age.

– Max heart rate can be affected by medications.

• Polar Heart rate monitors are great for measuring exercise heart rate.

Non-exercise Test VO2max Prediction Equations

• Direct measurement of VO2max is not always practical (time, expense, technical supervision).

• Several regression equations are available that predict VO2max using non-exercise test variables such as age, gender, body composition, and level of physical activity. See p. 13 packet.

• These equations broadly classify people as having poor, average, or good cardio-respiratory fitness.

Field Tests for Cardio-respiratory Fitness

• Several field tests have been developed that allow aerobic fitness to be estimated. – 1-mile and 1.5 mile run tests– 12-minute Walk/Run test– 1-mile walk test– Queen’s College Step Test

• These are practical, inexpensive, less time consuming than laboratory tests, are easy to administer for large groups, and quite accurate when properly administered.

• Refer to pp. 90-92 ACSM for procedures and equations to determine VO2.

• VO2 max norms are found on p. 14 in packet.

Run tests 1 or 1.5 mile run. Objective is to cover

the distance in the shortest time possible.

• 12 minute run: objective is to go as far as you can in 12 minutes.

• PACER test (Fitness Gram):– Used in schools to test CRE– Objective is to run as long as possible back

and forth across a 20 meter space at a pace which gets faster each minute.

Walk test• Originally developed by the Rockport

Shoe Company, based on research done to promote walking.

• Goal is to walk 1 mile as fast as possible.

• Is considered safer and easier than running, as the majority of Americans cannot run.

• It is valid for the elderly is they are accustomed to walking.

Interpretation of test results• Direct measurement uses actual

oxygen uptake to determine VO2• Indirect measurement uses:

– Time, speed or distance (workload)– Heart rate response– Use of a formula (regression equation) or

chart to estimate VO2

• VO2 scores are given a rating or classification

VO2 norms and classifications:

• Norms are based on statistical averages based on the groups tested

• Standards are developed based on those norms

• Standards can be different– Performance related– Health and fitness related

Interpretation of norms

• 90-100%= Excellent

• 75-88%= Very good

• 60-74%= Good

• 45-58%= Average

• 30-44%= Fair

• 15-28%= Poor

• 0-14%= Very poor

Classifications:• Women, ages 20-29

– Low= <28– Ave= 35-43– High= 49-53

• Men, ages 20-29– Low= <38– Ave= 44-55– High= 57-62

Classifications: (from ACSM)

• Women, ages 20-29• Low= <30• Ave= 33-36• High= 40• Men, ages 20-29• Low= <35• Ave= 41-44• High= 47

Other classifications:

• FitnessGram– HBZ= healthy benefit zone– “Needs improvement”– “Good”– “Better”

Sub-maximal Laboratory Tests• Less risky, less expensive, and requires less motivation than

maximal stress tests.• The sub-maximal exercise test (physiological response to a

fixed workload, or work required to reach a fixed physiological response) makes three assumptions (not entirely accurate however, causing a 10-20% error in estimating VO2max):– That a linear relationship exists between HR, oxygen update, and

workload– That the maximum HR at a given age is uniform (=220-age).– That the mechanical efficiency (oxygen uptake at a given workload)

is the same for everyone.• Oxygen uptake at any given workload can vary by 15% among

different people. In other words, people vary in the amount of oxygen they require to perform a certain exercise work load.– Some people are more efficient than others, and thus the average

O2 consumption associated with a given workload may differ significantly from one person to another.

• Sub-max stress tests tend to overestimate VO2 for those who are highly trained, and underestimate VO2 for the untrained (those with a high heart rate for a given workload).

•The reasoning underlying sub-maximal lab tests is that the person with the higher VO2 is able to accomplish a given amount of exercise with less effort (or more exercise at a particular heart rate).

Assessment of VO2 max• Sub-maximal Laboratory Tests

– Step tests • 1) Modified Canadian Aerobic Fitness Test• 2) YMCA 3-minute step test • 3) Queens College Step Test

– Treadmill tests• Typical cut-off point is 85% predicted max HR

– Bike tests• YMCA• Astrand

RPE scale, 0-10

Maximal Laboratory Tests

• The graded exercise test to exhaustion, with heart rate monitoring (with ECG in high risk individuals), is considered the best substitute for direct VO2max measurement.– Treadmill

• Bruce-most popular, followed by the Balke. • Naughton-used for cardiac patients.• Arizona State Univ. test for college

– Cycle• Astrand• Storer-Davis• Wingate Anaerobic