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Exercise decreases the risk for developing high blood pressure and chronic disease. This is largely a result of the positive changes that occur within our hearts and blood vessels.

Let’s talk about cardio (aerobic exercise).

What “dose” of aerobic exercise is recommended?

How often should it be? At least 3 days per week
How hard should it feel? Moderate-intensity*
How long per workout? 30-60 minutes 

*Objectively- 65-75% of maximum pulse rate. Calculate here. Subjectively- Using the talk test, during moderate-intensity exercise you can talk, but not sing.

While this will vary for individuals depending on their current health status, these are general recommendations to use as a starting point. For those with preexisting conditions you can consult with your physician before starting a new exercise program.

This is from the position stand of the American College of Sports Medicine, the largest sports medicine and exercise science organization in the world. They aim to, “advance and integrate scientific research to provide educational and practical applications of exercise science and sports medicine”.

A quick word of insight. I think the goal should be consistency (barring injuries or pain, for which a physician should be consulted). If you can only walk for 10 minutes at a time, no worries, take a break and get back at it. You will be improving your exercise capacity in no time. The good news is it’s never to late to begin and you have your entire life to improve. Just focus on personal growth. We all have different starting points.

Remember, “success is the sum of efforts - repeated day in and day out” -Robert Collier

Now let’s explore how this “dose” of exercise will benefit the body.

How do the heart and blood vessels adapt to exercise?

Aerobic training improves oxygen and nutrient delivery to active muscles, and strengthens our heart.

Cardiac output, described here, is the amount of blood pumped per minute (the product of pulse rate and stroke volume). Cardiac output is a large determinant of exercise capacity.

Pulse rate will increase with the intensity of exercise. Maximum pulse rate decreases with age, so to achieve a greater cardiac output, we can improve (or maintain) our stroke volume. Stroke volume is the volume of blood pumped by the heart with each beat. There are three main ways exercise improves stroke volume.

First, exercise causes more blood from the veins returns to the heart. This causes greater elastic recoil of the heart muscles and causes a more forceful heart contraction, resulting in more blood ejected into circulation.

Second, afterload decreases with training. This is the pressure the heart must overcome to eject blood into our blood vessels. The increased blood velocity to skeletal muscle causes small arteries, or arterioles, to dilate. The relaxed vessels allow for more blood to circulate.

Third, contractility and distensibility improve. Contractility is basically how hard the heart can contract to pump blood into the blood vessels. Greater distensibility means that the heart has a greater ability to stretch to accommodate more blood. Together the result is a greater volume of blood pumped per beat. 

So, exercise allows for stronger heart beats with more blood into relaxed blood vessels. As stroke volume improves with training, so does your cardiac output and exercise capacity.

We will learn more about how your body benefits to exercise in future posts. Until then feel free to leave your thoughts, comments, and questions.

Thanks for reading. Stay curious.



Editor(s): Austin Robinson, PhD

Curious to learn more? Check out these related resources. 

Aerobic activity intensity examples (Mayo Clinic):
Moderate intensity
-Walking fast
-Water aerobics
-Bicycling on mostly level ground
-Pushing a lawn mower

Vigorous intensity
-Swimming laps
-Fast bicycling or biking hills
-Playing basketball or soccer
-Playing singles tennis

Need a race on your calendar for motivation? Sign up for one here. Remember to continue staying active even after the race!
Want to see a heart beating using ultrasound? Check this out.
How about one beating outside the body? Look here.

What’s a cheap and easy way to monitor your pulse rate? The cheapest way would be to take your own take your pulse at the end of exercise manually. Recently, chest strap monitor (Polar H7) seemed to track best for accuracy, this is what I use. Here is the newer version, the Polar H10. You can grab a polar watch to go with it or connect the monitor to your phone using various fitness apps. (I am not affiliated with Polar at all and receive no royalties)