THE POWER OF HEMODYNAMICS
With any powered event, the ability to develop and sustain power is greatly determined by the ability to fuel the system. During exercise, the muscles and brain are supported by the cardio vascular system, which delivers oxygen, fuel for energy and removes waste via the blood.
At high outputs, endurance sport and motor sports, the demand for blood is high and it is essential high blood flow can be provided and sustained.
Blood flow refers to the speed at which the blood can move through the central and peripheral circuits. This determined by the cardiac output (ability to pump blood), total peripheral resistance (TPR) and the peripheral pump. These three effect blood flow and blood pressure, both important in performance.
Cardiac output is a function of heart size and heart rate. With improved fitness, the size of the heart increases to enable more blood to be pumped each beat helping sustain greater blood flow during exercise. Heart rate increases during exercise linearly with power, thus to increase your power output, you need to develop the ability to supply enough blood. By increasing heart rate you increase cardiac output and provide more blood flow.
Total peripheral resistance, is the internal resistance to blood flow. Upon exercise, the blood vessels dilate (expand) to allow greater blood volume to flow and maintain blood pressure. TPR is affected by cardiac output, the peripheral cardiovascular network and the peripheral pump. As cardiac output increases, TPR increases, requiring the heart to work harder in order to pump against the pressure and maintain flow, eventually leading to cardiovascular fatigue. Higher TPR restricts blood flow through he arterial circuit into the muscles and into the venous circuit.
Reducing TPR has a significant impact on endurance performance. Lower resistance allows the greater blood flow at lower cost/energy demand on the heart. High TPR has a detrimental effect on the cardiovascular system, limiting blood flow through the muscles and into the venous circuit and back to the heart. Reduced venous return decreases heart rate which decreases cardiac output.
The peripheral pump (muscles) helps return blood back to the heart through the venous system. See the peripheral pump article for the mechanisms affecting the peripheral pump.
Appropriate training will enhance peripheral hemodynamics (Cardiac output, TPR and peripheral pump), allowing more blood flow through the peripheral circuit. As you develop the ability provide more blood flow, the ability to produce more power will follow.
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