Can exercise be used to lower blood pressure? The phenomenon of post exercise hypotension is a well-recognized phenomenon. After a single bout of mild-to-moderate exercise, there is a sustained lowering of the blood pressure that can last for up to 13 hours in humans. This response is more pronounced in people with high blood pressure than in people with normal blood pressures. High blood pressure, being the leading risk factor for heart attacks, strokes, and chronic renal failure, makes taking advantage of post exercise hypotension especially beneficial to people with hypertension.
Scientific studies have shown that there are at least two processes involved in the generation of post exercise hypertension. There is a peripheral process that takes place in the muscles exercised and that involves the release of histamine. During exercise, histamine is released in the muscles exercised and causes vasodilation, which reduces peripheral resistance and lowers the blood pressure. This is the process that predominates after aerobic exercise. For unknown reasons, this is not the chief process that produces post exercise hypotension after resistance exercise. Even stranger is that this process is more active in women than in men.
With resistance exercise, post exercise hypotension is produced by a centrally acting mechanism involving the production of a neurotransmitter known as substance P. Resistance exercise stimulates the nerves in muscles that travel to the spinal cord and then to the brain. The impulses generated by the exercising muscles reset baroreceptors in the brain, thereby lowering the blood pressure. The stimulation of the brain receptors by substance P also decreases the cardiac output, the amount of blood pumped by the heart, and this further decreases the blood pressure. It is still unknown why this process predominates in resistance exercise, whereas in aerobic exercise, the histamine process predominates. It is very likely that both systems activate during either form of exercise, but with the preferences herein described.
Post exercise hypotension can be a double-edged sword. It is during this period of recovery that adaptations to physical training take place and generate physical fitness. Post exercise hypotension is also beneficial as a therapeutic and preventative measure for those people faced with high blood pressure. But, on the other hand, if this response is exaggerated, it can lead to post exercise syncope or light-headedness.
To prevent an exaggerated post exercise hypotensive response, several measures have been tried, including a period of cool-down exercises, aggressive rehydration, compression stockings, cold immersion after exercise, muscle contractions such as squats, and technique known as inspiratory resistance breathing. Taking antihistamines may also prove to be an effective measure for controlling post exercise hypotension and syncope/light-headedness.