Exercise and the Heart
I. Benefits of Exercise
II. Aerobic Exercise
III. Isometric, Static Exercise
IV. Weight Reduction and Exercise
V. Effects on Blood Pressure and Atheroma
VI. Effects on Blood
VII. Clinical Studies of Exercise and Heart Disease
VIII. Injuries During Jogging
IX. How to Start an Exercise Program
X. Exercise Stress Test
XI. Conclusion
GLOSSARY
afterload arterial impedance, restriction to blood flow delivered from the left ventricle; force against which the myocardium contracts in systole; a major determinant of wall stress.
angina pectoris short duration, recurrent chest pain or pressure often accompanied by feelings of suffocation and impending doom; most frequently associated with lack of blood and oxygen to the heart muscle.
arrhythmia general term for an irregularity or rapidity of the heartbeat, an abnormal heart rhythm.
atheroma same as atherosclerosis, raised plaques filled with cholesterol, calcium, and other substances on the inner wall of arteries that obstruct the lumen and the flow blood; the plaque of atheroma hardens the artery, hence the term atherosclerosis (sclerosis ¼ hardening).
fitness ability to undertake physical exercise without undue fatigue; the several types of fitness include aerobic, strength, coordination, and flexibility.
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- I. BENEFITS OF EXERCISE
One of the main reasons for practicing some form of regular, moderate exercise is that it always makes you feel and look better. Exercise does not have to be vigorous or strenuous to achieve important goals. Important psycho¬logical benefits can be produced by moderate exercise such as the combination of brisk walking for 20–30 minutes, performing stretching exercises for 10 minutes, and where possible, cycling or swimming for 10–15 minutes daily or at least every second day. These simple exercises are practical, inexpensive, and not time-consuming. - II. AEROBIC EXERCISE
Aerobic literally means ‘‘with air’’; that is, oxygen is required. Aerobic exercise involves the rhythmic contrac¬tion and relaxation of large muscle groups and movement of joints, for example, brisk walking, swimming, cycling, jogging, and dancing. - III. ISOMETRIC, STATIC EXERCISE
Isometric means ‘‘equal measure.’’ The muscle fiber length remains the same when muscular tension is exerted against a fixed resistance; that is, static exercise involves the development of tension within muscle fibers and results in little or no movement of bones and joints. Weightlifting and pushing against a wall are both examples of isometric exercise. Such exercise is also called resistance exercise. - IV. WEIGHT REDUCTION AND EXERCISE
A regular exercise program can cause mild weight reduc¬tion, which is greatly enhanced by a weight-reduction diet. Exercise is most helpful in long-term weight-reduction programs. Physical activity requires energy, which is measured in calories. Think of the body as having several factories. If you shut down half of these factories and let the other half work at half the speed, your output would be diminished. This is equivalent to turning down your metabolic rate (metabolic thermostat). If you go on a crash diet, your metabolic thermostat is turned down to get by on less food. Aerobic exercise 20–40 minutes done regularly three to four times weekly can boost your metabolic rate by 20–30%, and this will accelerate the breakdown of fat stores. The body of an obese individual is programmed to form fat and to store it away. In addition, your cells slow down and you burn fewer calories than normal. Cells slow down even more if you are on a severe weight-reduction diet to conserve energy. The more you exercise, the more dependent you become on fat metabolism. Many obese individuals do not overeat, but their metabolic rate is so low that they store fat. Therefore, start exercising first, then a few weeks later start your diet and continue on an exercise program for at least five years to keep the weight down. - V. EFFECTS ON BLOOD PRESSURE AND ATHEROMA
Blood pressure is not significantly lowered during vigorous exercise. During vigorous exercise such as five miles of jogging or 20 minutes of continuous aerobic exercise, the systolic blood pressure increases markedly in most individ¬uals. In many, the rise in blood pressure is substantial and it is possible that damage can occur in arteries during vigorous exercise. For example, a 40-year-old with a normal systolic blood pressure of 130 mmHg while running one to two miles, will usually have an increase in blood pressure during the run to about 150–180 mmHg. There is usually no increase in the diastolic blood pressure except in patients who have hypertension. Blood pressure rapidly falls on cessation of exercise and returns to the normal resting level within a few minutes. - VI. EFFECTS ON BLOOD
A. Plasma Lipoprotein Cholesterol - VII. CLINICAL STUDIES OF EXERCISE AND HEART DISEASE
Millions of North Americans participate in regular exer¬cise programs. This is a major achievement motivated by various advertisements and literature and the desire to feel fit and well and to possibly to stay alive longer. A few studies have suggested that cardiac death is more common in sedentary individuals than in the physically active, but further analysis of these studies revealed major defects in methodology and interpretation. Published studies on exercise and the risk of coronary heart disease lack standardization of the diagnosis of coronary heart disease, information on the effects of associated risk factors, and reliable evaluation of recreational or occupational physical activity. - VIII. INJURIES DURING JOGGING
The up and down motion of jogging causes tendon, muscle, and joint injuries. In one survey, about 1800 inju¬ries occurred in 1650 amateur runners. Injuries included: (1) Achilles’ tendonitis where the heel and the tendon become painful; (2) shin splints where the muscles at the front of the leg (frontal compartment syndrome) become painful and swollen; (3) painful knees with inflammation of the fluid-filled sac (bursitis), strain on ligaments, or painful knee caps (chondromalacia patellae); (4) painful feet with inflammation of the sole of the foot, plantar fasciitis, and trauma to the bones of the foot; and (5) exacerbation of arthritis of the hips, knees, and ankles. Patients with arthritis must not jog. Women are more susceptible to knee injuries or stress fractures in the pelvis, and in some, osteoporosis (loss of bone) may develop. - IX. HOW TO START AN EXERCISE PROGRAM
A. General Advice - X. EXERCISE STRESS TEST
Graded exercise testing introduced by Robert Bruce five decades ago remains an important diagnostic test for coronary artery disease. When coronary arteries become obstructed by atheromatous plaques, the supply of blood to the heart muscle becomes deficient and the muscle shows signs of ischemia that can be detected by the ECG. Ischemia is defined as a temporary lack of blood and oxygen to an area of cells for example the heart muscle, usually due to severe obstruction of the artery supplying blood to this area of muscle. Thus, the term ischemic heart disease is often used by physicians as it is the manifestation of coronary artery disease. - BIBLIOGRAPHY
Adams, V., Linke, A., Kra¨nkel, N. et al. Impact of regular physical activity on the NAD(P)H oxidase and angiotensin receptor system in patients with coronary artery disease, Circulation, 111:555–562, 2005.