Sid Valley Cycling Club - Basic Cardiovascular Physiology

Basic Cardiovascular Physiology

First, let's review the basic physiology of the circulatory system asking ourselves the question "What does the heart rate really indicate?" The components of the cardiovascular system are:

the heart (the pump)
the arteries (a distribution system)
the capillaries (the exchange system where gases, nutrients, and other chemical compounds move to and from surrounding tissue
the veins (which are the return circuit)

With every heart beat (contraction of the heart pump), a certain amount of blood (stroke volume) is pushed through the system. The contraction frequency of the heart is the heart rate (HR). The amount of blood moved to the cells of the body every minute is the product of the heart rate and stroke volume (HR x strove volume).

With physical activity (exercise) more oxygen is required by the muscle cells, and the circulatory system responds by increasing the heart rate (and the cardiac output). With aerobic training, the actual amount of blood pumped per heart beat (stroke volume) increases and the efficiency of the exchange process at the capillary level improves. The result is a lower heart rate for any level of physical activity in the trained versus the untrained individual. Thus aerobic training benefits include:

a lower resting heart rate
a lower heart rate for any specific level of exertion
as well as an increased exercise capacity for an individual's maximum heart rate.

The training effect results when the heart muscle is "stressed" by an increase in cardiac output (just as muscles in the arms and legs respond to the stress of lifting free weights). As the cardiac output is directly proportional to the heart rate, a heart rate monitor (HRM) can be used to structure and monitor an aerobic training program

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