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Effect of Exercise on Heart

Frequent and regular physical exercise is an important component in the prevention of some of the diseases of affluence such as heart disease, cardiovascular disease, Type 2 diabetes and obesity.

Exercises are generally grouped into three types depending on the overall effect they have on the human body:

Flexibility exercises such as stretching improve the range of motion of muscles and joints.
Aerobic exercises such as walking and running focus on increasing cardiovascular endurance.
Anaerobic exercises such as weight training, functional training or sprinting increase short-term muscle strength.

Physical exercise is considered important for maintaining physical fitness including healthy weight; building and maintaining healthy bones, muscles, and joints; promoting physiological well-being; reducing surgical risks; and strengthening the immune system.It is a common belief that training a particular body part will preferentially shed the fat on that part; for example, that doing sit-ups is the most direct way to reduce subcutaneous belly fat. This is false: one cannot reduce fat from one area of the body to the exclusion of others.

Most of the energy derived from fat gets to the muscle through the bloodstream and reduces stored fat in the entire body. Sit-ups may improve the size and shape of abdominal muscles but will not specifically target belly fat for loss. Instead, such exercise may help reduce overall body fat, affecting all parts of the body as determined by genetics. In fact, belly fat will often be the last fat removed from the body.

A recent review by Warburton, Nicol and Bredin (2006) examines the data of the benefits of regular physical activity, which is partially summarized below.

With both men and women, there is a 20%-35% relative risk reduction to all causes of death, including cardiovascular disease, for those who do the most physical activity (Warburton, Nicol & Bredin, 2006). An increase in energy expenditure to about 1000 kilocalories of physical activity a week (this is equivalent to walking one hour on five days of the week) is associated with a mortality benefit of about 20%.

From a different perspective, Warburton and colleagues note that physically inactive middle-aged women (who engage in less then 60 minutes of exercise per week) are at a 52% increase to all causes of mortality. The scientists further state that persons who are fit, yet have one or more risk factors to cardiovascular disease (such as hypertension, chronic obstructive pulmonary disease, diabetes, smoking, elevated BMI, and high cholesterol levels) are also at a lower risk of premature death then their sedentary counterparts.

In addition, it appears that there is a graded INDIRECT (or inverse) effect for those engaging in more (e.g. accumulating more time/week) physical activity and their associated risk reduction of death from all causes of mortality.

Thus, to summarize Warburton et al., there is indisputable evidence of the positive effectiveness of regular physical activity in the primary and secondary prevention of chronic diseases such as diabetes, hypertension, obesity, cardiovascular disease, some forms of cancer,
depression and osteoporosis. And, there clearly appears to be a linear association with increased
physical activity and improved health status.

Vigorous exercise elicits a greater energy expenditure then moderate exercise, and thus controlling for energy expenditure allows for the optimal way to assess the effects of aerobic exercise intensity.

All of the epidemiology studies that controlled for energy expenditure found greater cardioprotective benefits from the higher aerobic exercise intensities as compared to the moderate aerobic exercise intensities. As a matter of fact, no epidemiological study reported a greater cardioprotective benefit from moderate intensity versus vigorous aerobic exercise.

The clinical studies showed very similar results. When energy expenditure was controlled for in the study, the vigorous exercise intensity was more beneficial in altering one or more risk factors to coronary heart disease. Specifically, in relation to the coronary heart disease, the greatest cause of mortality in America, aerobic exercise of a more vigorous type resulted in lower incidence.

Regular physical exercise has been shown to play a critical role in the prevention and management of numerous chronic diseases including hypertension, diabetes, osteoporosis, obesity, cancer and depression (Warburton, Nicol & Bredin, 2006). However, Swain and Franklin (2006) state that the reason vigorous aerobic exercise provides greater cardioprotective benefits than moderate intensity exercise is presently unknown. However, it is well documented that vigorous exercise results in improved aerobic capacity.

In the long term, exercise helps the brain by:

increasing the blood and oxygen flow to the brain
increasing growth factors that help create new nerve cells
increasing chemicals in the brain that help cognition

Swain and Franklin hypothesize that a possible mechanism could be improved autonomic nervous system function (or tone). With regular aerobic exercise the sympathetic nervous system (that part of the autonomic nervous system that speeds up bodily processes) is reduced at rest while the parasympathetic nervous system (that part of the autonomic nervous system that slows down bodily processes) is increased (meaning it slows down cell process even more) at rest.

This major neurological system consequence from aerobic exercise may possibly be one of the underlying mechanisms that modulates (positively induces) many improved effects involved with coronary function; and thus be a foremost contribution to improved cardioprotective benefits. Swain and Franklin conclude their hypothesis with the fact that higher intensity aerobic exercise enhances these autonomic system tone changes.

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