Interval Training- The Hypothesis

By utilising short periods of high intensity exercise ( 3 to 5 minutes) interspersed with periods of low level of work lactic acid accumulation can be minimised.
At he high intensity work level increase fat burning occurs with reduction in fat stores. The need is to exercise at the anaerobic level but for periods of short duration thereby obtaining the benefits of reducing fat stores without increasing the risk of a significant metabolic acidosis with its consequences.

Based on the information above it is apparent that the most appropriate training for those patients with cardiovascular disease is one utilising the anaerobic interval.

Use of this level of training is however not without associated risks which may be summarised as follows:

• Complications based on the development of a degree of metabolic acidosis

Such complications are directly proportional to the lactate level.
Higher in the “high risk” patient
Higher in those patients with diabetes or renal failure
Higher in those patients with low fitness levels.
Higher in the obese patient
May result in varying degrees of heart block up to and including complete.

• Metabolic acidosis may occur prior to cardiac arrest in ischaemic patients

• Increased risk of ischaemic changes which may be silent

Silent ischaemia is present in a small but significant number of patients
Whilst most patients will develop associated symptoms these patients do not

• Increased risk of high grade ectopic activity

Ectopic activity can only be detected by cardiac monitoring
Ectopic activity which occurs at rest and disappears during exercise is generally more benign. High Grade ectopic activity may predict future cardiac arrest

• Is associated with biochemical changes including changes in potassium and magnesium levels which are detrimental to the myocardium.

The American Heart Association Heart Association in their scientific statement have provided risk classifications for patients depending on their clinical state and divided patients into four categories:

1 Class A Apparently Healthy Individuals
2 Class B Patients with known cardiac disease but low risk
3. Class C Patients with moderate to high risk of exercise
4 Class D Unstable Disease and activity Restriction.

Class A Apparently Healthy Individuals

Apparently healthy individuals

This classification includes:

1. Children, adolescents, men <45 years, and women <55 years who have no symptoms or known presence of heart disease or major coronary risk factors.
2. Men >45 years and women >55 years who have no symptoms or known presence of heart disease and with >2 major cardiovascular risk factors.
3. Men >45 years and women >55 years who have no symptoms or known presence of heart disease and with ≤major cardiovascular risk factors.

Activity guidelines:

No restrictions other than basic guidelines.

Supervision required:

None.

ECG and blood pressure monitoring:

Not required.

* It is suggested that persons classified as Class A02 and particularly Class A-3 undergo a medical examination and possibly a medically supervised exercise test before engaging in vigorous exercise.

Class B Known Stable Cardiovascular Disease

Presence of known, stable cardiovascular disease with low risk for complications with vigorous exercise, but slightly greater than for apparently healthy individuals

This classification includes individuals with any of the following diagnoses:

1. Coronary artery disease (myocardial infarction, bypass surgery, angioplasty, angina pectoris, abnormal exercise test, and abnormal coronary angiograms) whose condition is stable and who have the clinical characteristics as outlined below.
2. Valvular heart disease, excluding severe valvular stenosis or regurgitation with the clinical characteristics as outlined below.
3. Congenital heart disease; risk stratification for patients with congenital heart disease should be guided by the 27th Bethesda Conference recommendations.
4. Cardiomyopathy: ejection fraction of <30 percent; includes stable patients with heart failure with clinical characteristics as outlined below but not hypertrophic cardiomyopathy or recent myocarditis.
5. Exercise test abnormalities that do not meet any of the high risk criteria outlined in class C below.

Clinical characteristics (must include all of the following)

1. New York Heart Association class 1 or 2. None or slight shortness of breath.
2. Exercise capacity ≤6 METs. Equivalent to walking at 7kilometers/hour.
3. No evidence of congestive heart failure.
4. No evidence of myocardial ischaemia/angina at rest or the exercise test at or below 6 METs.
5. Appropriate rise in systolic blood pressure during exercise.
6. Absence of sustained or non-sustained ventricular tachycardia at rest or with exercise.
7. Ability to satisfactorily self-monitor intensity of activity.

Activity guidelines:

1. Activity should be individualized, with exercise prescription provided by qualified individuals and approved by primary healthcare provided.

Supervision required:

1. Medical supervision during initial prescription session is beneficial.
2. Supervision by appropriate trained nonmedical personnel for other exercise sessions should occur until the individual understands how to monitor his or her activity.
3. Medical personnel should be trained and certified in Advanced Cardiac Life Support. Nonmedical personnel should be trained and certified in Basic Life Support (which includes cardiopulmonary resuscitation).

ECG and blood pressure monitoring:

1. Useful during the early prescription phase of training, usually 6 to 12 sessions.

Adapted from: Fletcher,GF, Balady, GF, Amsterdam EA, et al. Circulation 2001; 104:1694. Copyright © 2001 Lippincott Williams and Wilkins.

Class C Moderate-to-high risk for cardiac complications

Those at moderate-to-high risk for cardiac complications during exercise and/or unable to self-regular activity or to understand recommended activity level.

This classification includes individuals with any of the following diagnoses:

1. Coronary artery disease with the clinical characteristics outlined below.
2. Valvular heart disease, excluding severe valvular stenosis or regurgitation with the clinical characteristics as outlined below.
3. Congenital heart disease; risk stratification for patients with congenital heart disease should be guided by the 27th Bethesda Conference recommendations.
4. Cardiomyopathy: ejection fraction of <30 percent; includes stable patients with heart failure with clinical characteristics as outlined below but not hypertrophic cardiomyopathy or recent myocarditis.
5. Complex ventricular arrhythmias not well controlled.

Clinical characteristics (any of the following)

1. New York Heart Association class 3 or 4. Marked or severe breathlessness at high work or rest.
2. Exercise capacity <6 METs. Unable to walk at 7 kilometres/hour.
3. Angina or ischaemic ST depression at a workload <6 METs.
4. Fall in systolic blood pressure below resting levels during exercise.
5. Non-sustained ventricular tachycardia with exercise.
6. Previous episode of primary cardiac arrest (i.e. cardiac arrest that did not occur in the presence of an acute myocardial infarction or during a cardiac procedure).
7. A medical problem that the physician believes may be life-threatening.

Activity guidelines:

1. Activity should be individualized, with exercise prescription provided by qualified individuals and approved by primary healthcare provided.

Supervision required:

1. Medical supervision during all exercise sessions until safety is established.

ECG and blood pressure monitoring:

1. Continuous during exercise sessions until safety is established, usually ≤12 sessions.

*Class C patients who have successfully completed a series of supervised exercise sessions may be reclassified to Class B providing that the safety of exercise at the prescribed intensity is satisfactorily established by appropriate medical personnel and that the patient has demonstrated the ability to self-monitor.

Adapted from: Fletcher,GF, Balady, GF, Amsterdam EA, et al. Circulation 2001; 104:1694. Copyright © 2001 Lippincott Williams and Wilkins.

Class D. Unstable Disease and Activity Restriction

Unstable disease and activity restriction*

This classification includes individuals with any of the following:

1. Unstable ischaemia.
2. Severe and symptomatic valvular stenosis or regurgitation.
3. Congenital heart disease; criteria for risk that would prohibit exercise conditioning in patients with congenital heart disease should be guided by the 27th Bethesda Conference recommendations.
4. Heart failure that is not compensated.
5. Uncontrolled arrhythmias.
6. Other medical conditions that could be aggravated by exercise.

Activity guidelines:

1. No activity is recommended for conditioning purposes.
2. Attention should be directed to treating the patient and restoring the patient to Class C or better.
3. Daily activities must be prescribed on the basis of individual assessment by the patient’s personal physician.

* Exercise for conditioning purposes is not recommended.

Adapted from: Fletcher,GF, Balady, GF, Amsterdam EA, et al. Circulation 2001; 104:1694. Copyright © 2001 Lippincott Williams and Wilkins.

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