Cardiorespiratory fitness

Cardiorespiratory fitness refers to the ability of the circulatory and respiratory systems to supply oxygen to skeletal muscles during sustained physical activity. Regular exercise makes these systems more efficient by enlarging the heart muscle, enabling more blood to be pumped with each stroke, and increasing the number of small arteries in trained skeletal muscles, which supply more blood to working muscles. Exercise improves the respiratory system by increasing the amount of oxygen that is inhaled and distributed to body tissue. A 2005 Cochrane review demonstrated that physical activity interventions are effective for increasing cardiovascular fitness.

There are many benefits of cardiorespiratory fitness. It can reduce the risk of heart disease, lung cancer, type 2 diabetes, stroke, and other diseases. Cardiorespiratory fitness helps improve lung and heart condition, and increases feelings of wellbeing.

The American College of Sports Medicine recommends aerobic exercise 3–5 times per week for 30–60 minutes per session, at a moderate intensity, that maintains the heart rate between 65–85% of the maximum heart rate.

The cardiovascular system is responsible for a vast set of adaptations in the body throughout exercise. It must immediately respond to changes in cardiac output, blood flow, and blood pressure. Cardiac output is defined as the product of heart rate and stroke volume which represents the volume of blood being pumped by the heart each minute. Cardiac output increases during physical activity due to an increase in both the heart rate and stroke volume. At the beginning of exercise, the cardiovascular adaptations are very rapid: “Within a second after muscular contraction, there is a withdrawal of vagal outflow to the heart, which is followed by an increase in sympathetic stimulation of the heart. This results in an increase in cardiac output to ensure that blood flow to the muscle is matched to the metabolic needs”. Both heart rate and stroke volume vary directly with the intensity of the exercise performed and many improvements can be made through continuous training.

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Wikipedia