• Elements of Exercise Prescription
  • Contraindications to Exercise
  • Risk Stratification
  • Blood Chemistries
  • Pulmonary Functions
  • Body Composition
  • Electrocardiography
  • Exercise Testing
    • Interpretation

RESOURCES

• American College of Sports Medicine, Guidelines for Exercise Testing and Prescription, Lippencott, Williams & Wilkins.

ELEMENTS OF EXERCISE PRESCRIPTION

Exercise prescription is the development of a specific exercise program based on a comprehensive evaluation. Whereas, exercise programming is basic exercise advice based on a limited evaluation. Neither exercise programming or exercise prescription can proceed without some kind of prior evaluation. Programming can include advice on physical activity.

Exercise prescriptions are more often given in the clinical setting where more precise guidelines are required for treatment of specific diseases. Whereas, exercise programming is more often utilized in the health and fitness setting where generic programs can be provided for large numbers of apparently healthy adults. On the other hand, many adults with controlled disease are found in the health & fitness industry. In these cases, the Fitness Specialist should comprehend the aspects of disease and the limitations of less comprehensive evaluations.

The elements of a complete exercise prescription are diagramed below.

Each of these elements change depending on the setting and the purpose of the exercise prescription. In addition, the methods to measure each element also changes depending on setting and purpose. The two extremes of spectrum are summarized in the table below

CONTRAINDICATIONS TO EXERCISE TESTING AND PRESCRIPTION

No matter what kind of exercise testing or physical conditioning is in order, the first step of the clinical evaluation is to determine if any contraindications to exercise exist. Contraindications to exercise must be continually evaluated. Some contraindications can be determined from a simple medical history or physical examination. Others require further laboratory procedures and perhaps, even stress testing to determine. Even after all the testing has been competed, contraindications for exercise training can still manifest.

Contraindications to exercise are not specific to the clinical environment.

The three main purposes for exercise testing are

1. Diagnostic and/or Prognostic
2. Therapeutic
3. Prescriptive

The purpose of diagnostic/prognostic exercise testing is to provoke certain conditions or disease so that it can be found and evaluated. The exercise test is more aggressive with larger work increments. The end point of the test is the detection of disease. The recovery is also designed to stress the heart more. The patient is usually put into the supine position to see how the heart responds to an increased venous return caused by the position.

Therapeutic exercise tests are designed to evaluate medical and surgical intervention and are similar to the diagnostic tests. In this case, a condition has been diagnosed for a patient and the patient has been either put on medication to control a condition or has undergone a surgical procedure to correct a problem. The purpose of this test is to see how effective the intervention was. For example, a patient presents to the physician with chest pain. The physician uses the diagnostic tests to determine the presence of angina and then prescribes medications to control the discomfort. The physician then performs another exercise test, the evaluation test, to determine if the medications can effectively control the angina.

On the other hand, the prescriptive test is to determine the functional capacity of the individual and to see how the heart rate and blood pressure respond to the work so that a safe and effective exercise prescription can be given. The test protocol is less aggressive with smaller work increments and an active recovery. The end-point of the test is usually 85% of heart rate max or a maximal voluntary effort.

Prior to any type of exercise testing, the contraindications must be determined based on the purpose of the test and the testing environment. What appears to be contraindications to exercise testing in one setting may not be in another. Although standards of practice should be taken into consideration, the medical director of the program is ultimately responsible for determining contraindications for that site.

The following contraindications were presented by the American College of Sports Medicine. These have been divided into two categories, Absolute and Relative.

Absolute Contraindications

A recent significant change in the resting ECG suggesting infarction or other acute cardiac events. Exercise testing in the presence of suspected infarction or other unknown cardiac events can further compromise the condition. For example, a silent infarct which has not been previously evaluated may reinfarct and cause more cardiac damage during exercise. These ECG changes should be referred to the physician to be evaluated before exercise testing can proceed.

In a prescriptive setting, these ECG changes are absolute contraindications. However, these ECG changes may be an indication for diagnostic/prognostic exercise testing as part of the evaluation process. Later, after medical or surgical intervention, exercise testing may be appropriate to evaluate the efficacy of the intervention.

Recent complicated myocardial infarction. A recent complicated infarct may become more compromised by exercise. However, low-level discharge exercise tests are frequently administered to uncomplicated infarct patients. In such cases, the enzymes and ECG changes must be stabilized prior to testing.

Unstable angina. Unstable angina is a recent change in anginal patterns. More than half of the post MI patients who survive the MI report that the nature or pattern of their angina changed before the infarct. The typical interval was approximately seven days. Therefore, changing anginal patterns indicates a worsening of the disease and probable infarct.

Uncontrolled ventricular dysrhythmia. Typical ventricular dysrhythmia include frequent PVCs, either unifocal or multifocal, couplets, and Ventricular tachycardia. These dysrhythmia compromise cardiac function because the abnormal beat often produces little or no stroke volume. Cardiac output may be decrease at rest and may not increase with exercise.

On the other hand, some ventricular dysrhythmia are diagnosed by exercise testing especially if they can not be provoked during a 24 hour Holter Monitor. In addition, the medications used to control the ventricular dysrhythmia may be evaluated by exercise testing.

Uncontrolled atrial dysrhythmia that compromises cardiac function. Common atrial dysrhythmia include atrial flutter, atrial fibrillation, and paroxysmal atrial tachycardia. In these dysrhythmia, the atria may not be contracting normally. The contribution of the atrial kick to the cardiac output may be absent. In addition, the ventricles may not get the signal from the atria to contract at a rate appropriate for exercise. Cardiac output may not increase with exercise in the presence of these rhythms.

On the other hand, diagnostic/prognostic exercise testing may used to evaluate the dysrhythmia and exercise testing to evaluate medical intervention may be used following administrations of medications.

Third degree A-V Block. A third degree heart block is a complete heart block or a complete dissociation between the beating of the atria and the ventricles. The atria and the ventricles are contracting at their own rate and the atria do not communicate the impulse to beat to the ventricles. The atria usually contract faster at a rate of 70 to 80 per minute; and ventricles usually contract around 30 per minute. This has also been called an idioventricular rhythm.

The slow ventricular rate is associated with a reduced cardiac output and therefore compromised blood flow. There are two types of complete heart block, congenital and acquired. These types are summarized in the table below. Acquired heart block is associated with 1) coronary heart disease, 2) hypertension, and 3) aortic valvular disease.

Exercise testing can be use to determine the efficacy and evaluation of the pacemaker.

Acute congestive heart failure. Congestive heart failure is a circulatory insufficiency resulting from a variety of etiologies. The heart is in congestive heart failure when it is unable to maintain stroke volume. Excess fluid blacks up into the ventricle, the atria and eventually the pulmonary system. Pulmonary edema as well as edema of the extremities results. Pulmonary edema leads to a cough and shortness of breath which can be detected at rest or during exercise. Cardiac output is compromised at rest in congestive heart failure. Exercise exacerbates the condition.

Patients with congestive heart failure can will often have exercise testing for prognostic evaluation. In addition, the efficacy of medications may also be evaluated through exercise testing.

Severe aortic stenosis. Aortic stenosis is a narrowing of the aortic valve. The narrowing presents an increased resistance to blood flow, an increased afterload, and increased work of the heart.
The work of the heart is compromised at rest in severe aortic stenosis. In addition, the blood flow to the coronary arteries is decreased because of increased ventricular pressures. Exercise further increases the work and subsequent demand for coronary blood supply. Ischemia, infarct, dysrhythmia, and loss of consciousness (via decreased cerebral blood flow) can result with exercise in severe aortic stenosis.

Mild cases of aortic stenosis can tolerate exercise well. In some cases, a patient with aortic stenosis will undergo a prognostic exercise test to determine if exercise is appropriate.

Suspected or known dissecting aneurysm. A dissecting aneurysm is a weakening of the vessel wall which causes a ballooning between the intimal and medial layers of the vessel wall. Atherosclerosis and hypertension are contributing factors. Because the ballooning is susceptible to rupture, the higher blood pressures of exercise must be avoided.

Active or suspected myocarditis or pericarditis. Myocarditis is an inflammation of the cardiac muscle tissue which can be associated with many types of infection. Pericarditis is an inflammation of the pericardial sac surrounding the heart and can result from many different causes from trauma to infarction. The treatment for both conditions is bed rest.

Thrombophlebitis or intracardiac thrombi. Thrombophlebitis is an inflammation and clotting of a vein and intracardiac thrombus is a clot in the chambers of the heart. Exercise is contraindicated because the higher blood flow and pressures during exercise can dislodge the clot. The typical recovery time for thrombophlebitis is 4 to 6 weeks during which time anticoagulants are administered.

Recent systemic or pulmonary embolus. An embolus is a clot or substance in the blood stream. A pulmonary embolus is in the pulmonary circulation whereas a systemic embolus is found in the rest of the circulation. Similar to thrombophlebitis, the higher pressures and flow during exercise may move the embolus to a vital area and cause infarct.

Acute infection.

Significant emotional distress (psychosis).

Relative Contraindications

Resting diastolic blood pressure >120 mm Hg or resting systolic blood pressure >200 mm Hg. Elevated pressures may reflect other conditions which may require further medical attention. Each blood pressure should be compared to previous pressures.

Moderate valvular heart disease. Rheumatic valvular disease, aortic regurgitation, mitral valve prolapse, and tricuspid disease are examples of moderate valvular disease. Rheumatic valvular disease is an alteration of the structure of the valve resulting from previous rheumatic fever. Regurgitation and poor opening are the major manifestations. The most common valves involved in rheumatic valvular disease are the aortic or mitral. Occasionally the tricuspid valve will be involved, however, the pulmonary valve is almost never involved.

The most common valvular disease found in women is mitral valve prolapse which is a falling down or dropping down of the mitral valve. Mitral regurgitation and frequent dysrhythmia are symptoms of mitral valve prolapse. A 2% mortality, more specifically sudden death during exercise exists.

Known electrolyte abnormalities (hypokalemia, hypomagnesemia). Hypokalemia, low potassium, and hypomagnesemia, low magnesium, increase the risk of exercise testing. In both cases, toxic responses, characterized by ventricular dysrhythmia, can be provoked by exercise. Diuretic medication for hypertension can lead to hypokalemia. Hypokalemia not only provokes dysrhythmia, but blunts the ST segment response making the ST segments uninterpretable.

Fixed-rate pacemaker. A fixed rate pacemaker improves the chronotropic action of the heart, but does not allow variation in the heart rate. In cases of exercise, where cardiac output increases via heart rate and stroke volume, a patient with a fixed-rate pacemaker will be unable to increase cardiac output adequately.

Exercise testing has also been used to evaluate dysrhythmia associated with exercise in the pacemaker patient.

Frequent or complex ventricular ectopy. Ventricular ectopy includes PVCs, either unifocal or multifocal, couplets, and short runs of V tach. Because ectopic beats are often associated with reduced ejection fraction, frequent and complex ectopy can compromise cardiac output, especially during exercise. Blood pressures should be monitored closely to insure adequate ventricular performance during exercise testing for individuals presenting with ventricular ectopy.

In addition, recent onset of ectopy may result in ventricular irritability secondary to an infarct. A probable infarct should be referred for evaluation prior to exercise testing.

Other indications of increased ectopy may include excess caffeine intake, mitral valve prolapse, digitalis toxicity, or any other type of condition that may require further evaluation before testing.

Ventricular aneurysm. A ventricular aneurysm is a ballooning of the ventricle associated with a massive myocardial infarction. Common locations of aneurysms are the anterior wall and the apex.
Because ventricular aneurysms are usually associated with hypertrophy, ventricular dysrhythmia, and congestive heart failure, caution must be taken in exercise testing and training.

Cardiomyopathy, including hypertrophic cardiomyopathy. Cardiomyopathy is a disease or abnormal condition of the cardiac muscle. Cardiomegaly is a hypertrophy of the heart, often of unknown origin.

Idiopathic Hypertrophic Subaortic Stenosis (IHSS) is a congenital condition characterized by enormous hypertrophy of the ventricle, usually the septum. Because the hypertrophy of the septum provides resistance to the blood flow, the hemodynamics are similar that found in aortic stenosis. In addition, these patients have a high risk of sudden death during exercise.

Uncontrolled metabolic disease. Metabolic diseases include diabetes, thyrotoxicosis, and myxedema. Chapter Eleven discusses Diabetes in detail. Both thyrotoxicosis and myxedema are associated with the thyroid gland. Thyrotoxicosis is a toxic condition due to a hypertrophy of the thyroid gland. It is associated with a rapid heart action. On the other hand, myxedema results from hypofunction of the thyroid gland and is characterized by anemia and mental apathy.

Chronic infectious disease

Neuromuscular, musculoskeletal, or rheumatoid disorders that are exacerbated by exercise.

Advanced or complicated pregnancy. Toxemia of pregnancy is a condition that affects some pregnant women later in gestation. It is characterized by an increased fluid retention which increases both the work of the heart and blood pressure. As a consequence, uterine blood flow is decreased and could be decreased more with exercise.

Heart disease in pregnancy has also been shown to decrease uterine blood flow during exercise in humans (Morris).

The first essential aspect of exercise testing is to determine the existence of these relative and absolute contraindications to exercise. Each contraindication must be evaluated in terms of the purpose of the exercise evaluation and the setting.

Information regarding the contraindications can be obtained from the medical history and physical examination as well as the laboratory testing itself.

RISK STRATIFICATION

Even though exercise is quite effective in the treatment of modern chronic disease, exercise has associated risk. Musculoskeletal injury is probably the most common, but the risk of heart attack and sudden death does exist. Although these risk have a low probability in cases of comprehensive evaluation, the outcome is catastrophic.

The risk associated with exercise testing:

• Sudden Death: 1/10,000 tests (0.01%)
• Heart Attack: 4/10,000 tests (0.04%)
• Complications requiring hospitalization: 10/10,000 (0.2%)

Risk associated with exercise training:

• Apparently Healthy Adult
  • Morbidity: 1/887,526 participant hours
  • Mortality: 1/1,124,200 participant hours
• Cardiac Patient
  • Morbidity: 1/34,673 participant hours
  • Mortality: 1/116,402 participant hours

Levels of Risk

Risk factors for coronary heart disease:

To establish the number of risk factors, add up the number of positive (black) risk factors and subtract the number of negative (green) risk factors. This final sum is the number of risk factors used to establish low and moderate risk.

For the high risk stratification, signs and symptoms suggestive of cardiovascular and pulmonary disease are used in conjunction with the actual diagnosis of disease. These signs and symptoms are listed below

• Pain, discomfort (or other anginal equivalent) in the chest, neck, jaw, arms, or other areas that may be due to ischemia
• Shortness of Breath
  • at rest
  • with mild exertion
• Dizziness or syncope
• Orthopenia or paroxysmal nocturnal dyspnea
• Ankle edema
• Palpitations or tachycardia
• Intermittent claudication
• Known heart murmur
• Unusual fatigue or shortness of breath with usual activities

If a patient presents with one or more of these symptoms or if the patient has been previously diagnosed with cardiovascular, pulmonary or metabolic disease, their risk stratification is High.

Tools used to access information for risk stratification include: Physical Examination Laboratory Blood Reports Medical History Health Habits Body Composition Analysis Exercise Testing Different methods to obtain this information will be used in different settings. The most basic assessment for moderate physical activity in the absence of any evaluation is the Par-Q. The Par-Q was developed by the Canadian government in the 1070s as a public health movement (ParticipAction) to encourage exercise across the country. The questions from the original Par-Q are: Has your doctor ever said that you have a heart condition? Do you frequently have pains in your heart or chest? Do you often feel faint of have spells of severe dizziness? Do you take medication for blood pressure or for your heart? Has your doctor ever told you that you have a bone or joint problem such as arthritis that has been aggravated by exercise, or might be made worse with exercise? Is there a good physical reason not mentioned here why you should not follow an activity program even if you wanted to? Are you over 65 years old and not accustomed to vigorous exercise? If the participant answers NO to all the questions, they can begin a moderate exercise program. If they answer YES to any one of the questions, they should consult their physician before starting an exercise program. In 2002, the Par-Q was revised:   Keep in mind, the Par-Q does not establish risk. It cannot be used for risk stratification. It does not access Overweight & obesity Cholesterol Glucose Diabetes Family History Smoking Physical Inactivity Hypertension not on meds ACSM developed a questionnaire that addressed risk factors, but does not measure them.

BLOOD CHEMISTRIES

Blood chemistries are often cheaper by the dozen. So, a blood report will have more types of blood chemistries than required to evaluate the client/patient for exercise. The components of the blood report include:

• Lipids
• Enzymes
• Electrolytes
• Sugars
• Cell Counts
• Others

The purposes of these reports for exercise testing and prescription include:

1. Establish Risk
   The lipid panel gives values for Total Cholesterol, HDL Cholesterol and Triglycerides. LDL Cholesterol can be calculated from Total Cholesterol and Triglycerides.
   
   Fasting blood glucose provides information on impaired glucose as well as glucose control in diabetes.
   
   
2. Effects of Medications
   Some medications, like diuretics, can affect potassium concentrations. Because low potassium can be fatal during exercise, screening the potassium is a safety issue. If the potassium is too low, refer the client/patient back to their physician for management.
   
3. Further Screening
   Other blood chemistries may be abnormal and may require referral back to the primary physician.
   
4. Nutritional Assessment
   The nutritionist observes the blood chemistries to see nutritional status.

Each health or disease condition requires a different blood work-up. The general work-up in apparently healthy adults is listed below. This would be from a simple Complete Metabolic Profile (CMP).

BLOOD PANELS FOR DISEASE STATES

Some disease states require a variation in the blood analysis:

• DIABETES
  • Glycosylated Hemoglobin - Hb_A1c
  • Glucose Tolerance Test

PULMONARY FUNCTIONS

Of all the assessment activities, pulmonary function are often the least utilized. The assessment of pulmonary function is important in the diagnosis and evaluation of obstructive and restrictive pulmonary diseases.    Obstructive lung disease is clinically identified by a decrease in expiratory flow rates, the anatomical basis of which is airway narrowing.   Whereas, restrictive lung disease is clinically identified by decreased lung volumes.   Pulmonary functions utilized in the diagnosis and prognosis of these diseases include:

• Static Lung Volumes (VC)
• Flow Rate (FEV₁)
• Flow-Volume Loops
• Maximal Ventilatory Volume (MVV)

Pulmonary functions are not the only means of evaluating lung disease.  Other assessments include:

• Diffusion Capacity
• Arterial Blood Gases
• Right to Left Shunts

    Vital capacity maneuver measures dynamic and static lung volumes. Static lung volumes are single volumes whereas dynamic volumes or capacities are combinations of static lung volumes.

    The graph to the right illustrates the vital capacity maneuver.  It starts with normal tidal breathing.  Then you see the complete inhalation followed by the complete and rapid exhalation.  Then normal tidal breathing continues.

Each component of the forced vital capacity maneuver is divided into different pulmonary functions.

Dynamic pulmonary functions are:

• Inspiratory Capacity
• Vital Capacity
• Functional Reserve Capacity
• Total Lung capacity

Whereas the static pulmonary functions are:

• Inspiratory Reserve Volume
• Expiratory Reserve Volume
• Tidal Volume
• Residual volume is a static lung volume, but cannot be measured by the Vital Capacity Maneuver

Diagnostic criteria, based on pulmonary functions

FEV₁ is the percent of the vital capacity that can be exhaled within the first second.

A FEV₁ <60% compromises the ability to exercise.

The forced vital capacity maneuver can be illustrated in a different way; as a flow-volume loop.

Flow rate is plotted on the y axis whereas volume is plotted on the x axis. These values are plotted for every fraction of a second of the total inspiration and expiration. The expiration is above the x axis whereas the inspiration is below.

The plot begins at total lung capacity; with the lungs filled as much as possible.

Different pulmonary diseases exhibit distinct flow-volume loops.

Flow rates are also broken down into fractions of the whole maneuver. That is:

• 25%
• 25-50%
• 25-75%

    MVV measures the capacity to move air in and out of the lungs.   MVV is illustrated in the figure to the right.   MVV measures the largest amount that can be moved in 10 or 20 seconds and corrects that volume to one minute. The MVV has been called the huff and puff test.   It is a series of rapid deep breaths for 10 to 20 seconds.

Relationships among Pulmonary Functions and Physical Work Capacity

Pulmonary functions are assessed in pulmonary disease and are used in the exercise prescription. The only need for measuring pulmonary functions in the health & fitness setting would be for heavy smokers or incorporating exercise in a smoking cessation program.

BODY COMPOSITION

The assessment of body composition in the health and fitness industry, as well as in the clinical setting, can provide useful information in assessing risk of metabolic and cardiovascular disease and providing healthy target weights.

There are many ways to assess body composition. These ways are summarized on the K536 Overweight and Obesity website. For the most part, the Bod Pod, anthropometry, Near-Infared Interactance, and bioimpediance are the most common techniques used in the health & fitness industry. None are accurate; especially with poor training and poor control of factors.

In the clinical setting recommendations can be found at:

In the research setting, Bod Pod, Computed Tomography, Magnetic Resonance Imaging, and Dual X Ray Absorptiometry are most often used.

body fat distribution and total body fat can be utilized to make recommendations for health.

• If your client/patient exhibits an upper body distribution of body fat, weight loss is more critical.
• Target weights in exercise prescription and programming are based on health or risk of disease rather than athletic performance.

Calculating Target Body Weights

Because >33% for women and >25% for men are considered at risk, targeting weight to be under these values should reduce risk.

Good policies in recommending target weights:

1. Give all target weights in ranges of 5%.
2. Give short term (6 months) weight loss goals as 3-5% below current weights
3. Give long term weight loss goals
   1. 25-30% for women
   2. 18-23% for men

The steps to determine target weights:

1. Determine fat weight (FW) from total body weight (TW) and percent fat (%F).
2. Determine lean weight (LW) from total body weight and fat weight.
3. Choose the target percent fat.
4. Convert the target percent fat to target percent lean
5. Calculate target weights (TarWt) from target lean (TarLe) and lean weight.
6. Round up your target weights to the nearest whole number

1. FW = TW x %F
2. LW = TW-FW
3. Women 25-30% or men 18-23%
4. Women 70-75% lean or men 77-82% lean
5. TarWt = LW/(TarLe x 100)

Re-evaluate body composition every six months for individuals who want to lose weight.

ELECTROCARDIOGRAPHY

Electrocardiography measures the electrical activity of the heart and assumes the mechanical action follows. The ECG is the single most important screening tool for the diagnosis of coronary heart disease. It is the single criterion for positive and negative exercise testing.

ECG can provide information on

• Rhythm
• Ischemia
• Infarct
• Size
• Location
• Electrolyte Imbalance
• Pericarditis

The placement for the limb leads for a standard resting 12 lead electrocardiogram are illustrated on the left hand figure. The placement during exercise are illustrated on the right hand figure. This is called the Mason-Likar system.

ECGs during exercise are therefore different than standard resting 12 lead.

Supine and standing 12 leads are analyzed prior to exercise to rule out recent infarctions and/or recent changes in ECG as contraindications for exercise.

The ECG is observed continuously throughout the exercise test and during recovery.

It is more prudent to look at leads that represent the

• left ventricle
• right ventricle
• inferior heart

than to look at all leads that reflect the left ventricle.

EXERCISE TESTING

When exercise testing is used in the clinical setting the testing is often called Stress Testing. Whereas exercise testing used for exercise prescription is often called Graded Exercise Testing or GXT. The purpose of the stress testing is to find disease whereas the purpose of the GXT is to evaluate functional capacity and to prescribe exercise. To compare characteristics of stress testing to GXT, see the table below.

In the health and fitness setting exercise testing includes strength and flexibility testing. For the most part, exercise testing in the clinical setting is limited to cardiovascular function. Strength and flexibility testing are utilized in the clinical setting when the patient exhibits co morbidities in neuromuscular or musculoskeletal diseases.

Most supervised tests are continuous with increasing intensity each stage. Other types of tests include:

• Single stage
• Intermittent
• Ramp

Modes of testing include:

• Treadmill (walk or run)
• Cycle ergometer
• Arm Crank
• Step Testing
• Timed Walk/Run

The most simple exercise testing would be a single stage step test. Whereas the most complex would be a graded exercise test to maximal capacity with the measurement of VO₂max.

The most common exercise test recommended for the health and fitness setting is a graded submaximal cycle ergometer test. The most common test performed in the clinical setting are graded submaximal treadmill tests.

When submaximal tests are used, the test must end beyond the intensity prescribed for the client/patient

.

An important decision about test protocols is, "should the test be maximal or submaximal?" Most tests in the clinical setting are submaximal with the end point being 85% of heart rate max. However, according to the work of Cumming and colleagues, 50% of the individuals who exhibited a positive electrocardiographic response to maximal graded exercise testing would have been missed had the test terminated at 80% of heart rate max (British Heart Journal 34:919, 1972). Had these individuals been tested to 80% heart rate max, yet prescribed exercise intensity above the 80%, they may have been in danger of an adverse event during exercise. If you choose to perform a submaximal GXT, you need to realize that you may have missed vital information.

Variables measured during exercise testing are summarized below. Variable measured at rest and in recovery have an asterisks:

The first five are the most important in a health & fitness setting.

INTERPRETATION OF EXERCISE TESTING

All the variables measured during the GXT need to be interpreted. In that interpretation, a conclusion (positive or negative) for the test needs to be made.

PHYSICAL WORK CAPACITY - (PWC) is the outcome variable for any GXT. It is a measure of the cardiorespiratory endurance. It gives an indication about the types of activities that the client/patient will be able to perform.

The most direct measure of physical work capacity is VO₂max or VO₂peak as it should be called in the clinical setting. If expired gases were not collected during the test, the VO₂peak can be estimated from the ACSM metabolic equations.

Ending workrate provides a measure of physical work capacity if VO₂max is not measured. In any case, the ending work (estimated or measured) is compared to predicted.

Conclusions are:

• Higher than predicted for age and physical activity
• Within limits of predicted for age and physical activity
• Below predicted for age and physical activity

HEART RATE - The heart rate may be the single best indicator of heart work. Heart rate has a normal response to graded exercise. The athlete often exhibits an increases of 4-8/min for each increase in MET; whereas sedentary adults increase 8-12/min for each MET increase. Obesity can exhibit as high as 18/min per MET increase.

As the workrate increases, the heart rate should also. Medications such as Beta Blockers blunt the heart rate response. It is not unusual to find a maximal heart rate of 125/min for a person on beta blockers who should have a predicted HRmax around 150 per minute. If the client/patient is not on beta blockade medication, however, the heart rate response is abnormal. Anxiety HR response would increase rapidly, then exhibit a normal heart rate where it becomes normal. Similarly, the maximal heart rate should be within predicted. HRmax = 220-age (+ 12/min)

A conclusion should be documented regarding the heart rate response as well as the maximal achieved..

RATED PERCIEVED EXERTION- RPE is often not interpreted, but used for exercise prescription to help the client/patient guide exercise intensity.

BLOOD PRESSURE - BP is probably the variable measured during the test that provides the best information on exercise tolerance. In the clinical setting Systolic Blood Pressure represents cardiac output and Diastolic Blood Pressure represents vascular resistance to blood flow.

Systolic blood pressure should increase progressively through graded exercise because cardiac output should increase for each increase in workrate. Diastolic blood pressure should stay the same or decrease because resistance to blood flow should not increase during scenarios of increased blood flow. The mean systolic blood pressure response to graded exercise is: 7.5 mm Hg/MET Hypertensive response is >12 mm Hg/MET Hypotensive response is <5 mm Hg/MET

The hypotensive systolic blood response means the cardiac output is not increasing with the workrate. The heart is failing to adjust to the workrate. Several factors could contribute to the hypotensive response:

• ECG rhythm abnormalities
• ECG ischemic responses

A drop in systolic blood pressure is an indication to terminate the test early. A drop in systolic blood pressure with an increase in diastolic pressure is immediate termination.

Putting the HR and BP response on the same graph, SBP is most often greater than HR. However, it is not unusual in young women to find HR greater than SBP. In the Beta blockade response, both HR and SBP will be significantly lower. The SBP response to anxiety is similar to the HR response.

ECG - The ECG is the single criterion used to determine whether the test is positive or negative. Although, often symptoms, blood pressure, and physical work capacity is also used in the determination of positive/negative testing.

The ST segment of the ECG is the part of the ECG that is used in this evaluation.

ST segment depression indicates an area of the heart is ischemic. Ischemia means low blood flow. Low blood flow occurs when the blood flow cannot match the work demand for it. Atherosclerotic lesions are the primary cause of ischemia during exercise testing. ST segment >1 mm of horizontal depression, for at least 0.80 seconds following the J-point in three consecutive complexes; and is the clinical definition of ischemia and a positive stress test.

If an exercise ECG does not exhibit ST segment depression it is a negative test.

In other cases, an abnormal blood pressure response in the absence of a positive ECG may have medical follow-up.

ST segment elevation indicates an area of injury. This means a heart attack is happening. An exercise test should be terminated immediately if this exhibits during testing. If this exhibits before testing, testing should be cancelled and the patient should go to the ER.

SYMPTOMS - Symptoms important during exercise testing include:

1. Muscle or skeletal
2. Shortness of Breath or Dyspnea
3. Light handedness
4. Dizziness
5. Ischemic symptoms
   1. Angina or chest discomfort
   2. Shortness of breath
   3. Excessive Sweating
   4. Pallor
6. Color of skin
7. Other

Symptoms often accompany ischemia. The classic symptom is angina, a chest discomfort. Other signs of ischemia, in the absence of angina, include shortness of breath, excessive sweating and/or pallor. These symptoms will often be accompanied by a drop in blood pressure; although can occur without a drop.

Angina can be a discomfort anywhere above the waist. It is not a sharp pain. It is pressure, heaviness, or burning. It is typically in the chest and radiates to the left arm. But it can be in the jaw or back. It is relieved by rest or nitroglycerine.

Angina and dyspnea are measured on specific scales.

Dyspnea is more often measured in pulmonary patients.