Sports

Better understanding the science of heart health

Since February is Heart Month, it is a good time to remind ourselves how important exercise is for the heart and cardiorespiratory system as a whole.

But save for knowing that the heart speeds up while exercising, not many people realize the extensive and intricate processes that go on within the body once you start. Immediate changes begin to happen during the first minutes of your workout – even if you are out of shape and haven’t exercised in years. Here then, are just some of those amazing changes.

Once your mind has motivated to move you to walk, run, cycle, swim, play or work, signals are sent to the muscles causing contractions and begin the process of burning energy. This starts a chain reaction of chemicals and hormones being released that effects every part of your body.

But even before you start moving, hormones from the adrenal gland are released in anticipation and this stimulate the heart to change. The heart not only increases how fast it contracts (heart rate), but also the volume of blood it pumps with each contraction (stroke volume).

More blood fills the chambers of the heart, the recoil of the muscle wall is higher, producing a more forceful contraction. Stroke volumes in non-athletes average around 50 milliliters per beat and can increase up to just over 200 ml/beat in an elite athlete.

Blood flow at rest is about five litres per minute, but during more intense exercise, it can increase to around 35 litres per minute in elite athletes. Think about how much liquid 35 litres is – just over a litre every two seconds pumping through your heart.

In order to be able to do this, the body makes some other immediate changes in blood flow. First, the autonomic nervous system and adrenaline redirects the flow to the muscles and skin to aid in more oxygen getting to the working muscles, and to cool the body through sweating. At rest, the muscles get about 20 per cent of the available blood flow, but this increases to about 80 per cent during heavy exercise.

Hormonal and nervous changes along with substances such as lactic acid and carbon dioxide also help to dilate the peripheral blood vessels. This relaxes the ‘smooth’ muscle cells in the walls of the vessels of large veins and arteries, but also in the small arterioles that feed the working muscles (including the heart muscle).

Dilating the vessels allows more blood to pass through to reach the muscles.

One major benefit for those who begin to exercise on a regular basis is that it stimulates the body to grow more small blood vessels around the heart, lungs and in the muscles, and this helps to lower blood pressure and keeps the heart well-supplied with blood, reducing the chances for heart attack.

Finally there are many other acute effects of a single exercise session, including the release of endorphins (which make you feel good and help you have an optimistic outlook), more blood flow to the brain (increased concentration), hormonally controlled release of fat and carbohydrates into the blood stream, and improved insulin sensitivity (which can help reduce risk of diabetes).

These are just a few of the many amazing processes that happen in your body when you exercise.

Consider these the next time you are debating whether or not to get in some activity or while you are enduring the first few minutes of exercise.

Kerry Senchyna holds a bachelor of science degree in kinesiology and owner of West Coast Kinesiology in Maple Ridge.

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