Basics · Fitness

Cardio: The heart of the matter

I recently bought a FitBit Charge HR. I love that it tracks my heart rate and automatically detects when I’m exercising. That is, it automatically detects when I’m doing cardio and logs that information into its app. At first, this annoyed me. I want to see every workout on there. If I do it, I want credit for it! So why would the FitBit only care about cardio?

First, because that’s the way it’s designed. I mean, your heart rate has a direct connection to your cardiovascular fitness and the FitBit Charge HR monitors your heart rate. It makes sense, right? Second, cardio is kind of a big deal. In fact, it is essential to achieving overall health and fitness and is the only type of exercise that strengthens the heart.

During cardio workouts, there are two main systems at play, the cardiovascular system and the respiratory system. Throughout the rest of this article I will sometimes refer to them separately and sometimes refer to the two systems working together as one – the cardiorespiratory system.

start with your heart

Here’s a basic rundown of how the cardiorespiratory system works. When you breathe in, your lungs fill with oxygen. That oxygenated blood is transported to the heart where it is then pumped to the rest of the body. As the blood travels through your arteries, it “drops off” oxygen and other nutrients and “picks up” waste, such as carbon dioxide. Your veins carry that oxygen depleted blood back to your heart. It is then pumped back to your lungs, where the waste is dumped (exhalation) and more oxygen is loaded (inhalation).

Remember this about the cardiorespiratory system:

  1. It delivers nutrients throughout the body.
  2. It removes waste from the body.

While exercising, your muscles require more oxygen than when at rest. As you exercise, your heart rate increases because your heart works harder to keep up with the demand of your muscles. As your heart gets stronger, the amount of blood it can pump increases, which means your muscles receive more nutrients. When your muscles are supplied with more oxygen, you perform better. Cardio also helps to lower blood pressure, decrease your risk of diabetes, increase your bone density, lower your cholesterol, and improve your sleep quality. Basically, cardiorespiratory fitness increases your quality of life.

Cardio exercise is anything that increases your heart rate for a sustained amount of time. If your heart is pumping hard and you’re breathing heavy, you’re doing cardio! If you’re just starting out, pick activities that are considered moderate intensity. As your heart gets stronger and your body gets more efficient, go big! Challenge yourself to exercise at a vigorous intensity. Here’s a quick reference for you.


  • Walking briskly (20 minute miles)
  • Water aerobics (some, not all)
  • Bicycling slower than 10 miles per hour
  • Tennis (doubles)
  • Ballroom dancing
  • Gardening


  • Race walking, jogging, or running
  • Swimming laps
  • Tennis (singles)
  • Aerobic dancing
  • Bicycling 10 miles per hour or faster
  • Jumping rope

Vigorous activities require more effort and put more stress on your cardiorespiratory system than moderate activities. Because of this, vigorous activities burn more calories. Keep in mind that the lists above are just examples, and the level of effort required may vary from person to person based on their overall level of fitness. You get out of it what you put into it, so don’t hold back.

To know which intensity level you’re really exercising at, do the talk test. If you can talk but not sing, you’re exercising at a moderate intensity. If you can only speak one or two words before taking a breath then you’re exercising at a vigorous intensity. If you can sing, well, it’s time to get moving!

FitTip: Including cardio exercises into your routine is a must if you want to be healthy. To have a real impact on your cardiorespiratory system, you should perform cardio exercises at a moderate level (at least!) for 30 minutes three to five days a week. When exercising, breathe in deeply, allowing your chest to expand and rise, and then allow your chest to fall as you breathe out. This is how you collect all that oxygen your body needs. Learning to breathe correctly will power your workouts and help you keep moving for longer periods of time.


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