Dear Sarah,

We are often told that first and foremost exercise is essential to keep our hearts healthy. As I like to walk to work (it takes about 40 minutes and I walk briskly), I'm wondering if this is enough exercise to keep my heart in tip-top shape, or do you think I need more? And can you tell me how exactly exercise benefits the heart?
Thanks,
Lisa

Dear Lisa,
Your heart is the most important muscle in the body, far more important than that six-pack you have been longing for! Unfortunately, heart health often falls off our radar, which is probably why heart disease is becoming one of the biggest epidemics -- and greatest challenges -- in our culture. According to the American Heart Association, 910,000 Americans die each year due to cardiovascular disease. That is equivalent to the death toll of 9/11, every 27 hours. Canadians are not any better -- the number of overweight and obese Canadians according to the Canadian Community Health survey is 59 percent. And yet, cardiovascular disease is the number one most preventable disease.

Get to Know Your Heart...
Your heart is located to the left of the centre of your chest, and is about the size of your fist. Your heart muscle is a double pump; the right side receives blood from the veins of your body and pumps it into your lungs, and your left side receives oxygenated blood from the lungs and pumps it out through your arteries into the rest of your body.

To better understand the heart, think about the common phrase "in a heart beat": Before each beat, your heart fills with blood, the heart muscle contracts and pushes the blood along. Your heart does this all day and all night without 'missing a beat'. Did you know that your heart pumps blood to every cell of your body in less than 60 seconds?

Your body needs a steady supply of blood to keep it running just like gasoline in your car. And when you are exercising, your body needs more oxygen-filled blood so your heart pumps faster to give your body what it needs. The goal of cardiovascular training is to teach your heart to pump at an accelerated but steady pace.

How Can Exercise Help Your Heart?
A healthy heart should beat with a fairly regular rhythm that will change based on levels of exertion and oxygen requirements. A healthy heart has a high stroke volume, which refers to the amount of blood that is pumped out with each beat. And a healthy heart does not have to work as hard to pump blood and that is why you need to do cardiovascular training. Cardiovascular exercise elevates your heart rate and increases the size of your heart, which in turn increases the stroke volume and thus results in lowering your resting heart rate. Cardiovascular exercise can also increase the concentration of hemoglobin in blood, allowing the body to become more efficient at transporting oxygen to your cells.

Cardiovascular exercise also combats three major factors related to heart disease: stroke, obesity and stress. Exercise not only burns calories by making your body work harder, but it also increases you metabolism ( rate at which you burn calories), thereby reducing body fat. Elevated cortisol and lack of proper rest are major contributors to stress. Exercise releases endorphins (the feel good hormones) and reduces cortisol (stress hormones) and helps you sleep better.

How Much Exercise Do You Need?
In general, to achieve maximum benefits, you should gradually work up to an aerobic session lasting 20 to 30 minutes, at least three to four times a week. Exercising every other day will help you keep a regular aerobic exercise schedule. Your intensity should be 60-70 percent of your max heart rate (max heart rate = 220-age). You may want to mix in some high intensity bursts into your routine, which create a greater workout for your heart (and burns more calories). Briskly walking will not get your heart rate up to 60-70 percent of your max heart.

Although cardiovascular exercise can be as simple as jumping on a treadmill or diving into the pool or hopping on a bike, consider making it more exciting. Learn a new sport such as hockey, basketball, ultimate Frisbee or tennis. Or mix up your routine and swim one day, ride your bike the next, go running after that and so on.

Sarah Brown is a very healthy woman. She is not only a fitness instructor at Goodlife where she teaches Body Pump, Body Flow and yoga but she is also a Certified Nutritional Practitioner. If you have a question for Sarah, leave a comment below and she will try and help, but note that not all questions will be answered.