Getting in the Zone

UGH. Poor Little C is sick yet again. Yesterday preschool called to say she had a fever and she has been feeling pretty miserable. She got up at 5am this morning (double ugh) so I’m a tired mommy this morning. So instead of focusing on the 4 hours of broken sleep I got last night, let’s focus on cardio. Since I’m all about getting down to the basics on this blog, it would be negligent of me not to talk about cardio, weight-loss, and how the two really aren’t as synonymous as we are lead to believe. To better understand your body, weight loss, and maintaining a healthy lifestyle, you first have to understand heart rate and how it plays a major role.

The fitness community, trainers, all of us have been trained to use weight-loss exercise and the term “cardio” synonymously when in fact this is really not the case. In fact, there are several heart rate “zones” and each one effects the body differently.

Cardiovascular exercise is defined as “physical exercise of relatively low intensity that depends primarily on the aerobic energy-generating process”. Aerobic literally means “relating to, involving, or requiring free oxygen”, and refers to the use of oxygen to adequately meet energy demands during exercise via aerobic metabolism.

In the last ten years or so there has been a lot of talk about the “fat-burning zone”, but this terminology is actually rather misleading. This fat-burning zone occurs at a lower-intensity level (between 55 and 72 percent max heart rate) when fat oxidation rates are at their highest. When you exercise at a low-intensity level, a larger percentage of calories burned are coming from fat stores rather than carbohydrate stores; about 60 percent of the calories burned come from fat. The key to this kind of cardio is that it can be performed for long periods of time (so no sprints, intervals, etc) and is also known as steady-state cardio or long duration cardio.

So I’m sure right now you’re thinking, “ok, great, I’ll just do lots of low-intensity long distance runs and walks and easy bike rides” but before you write off intervals and sprints, there is more to weight-loss than just staying within the fat-burning zone. The cardio zone is a step above the fat-burning zone, and is defined as aerobic exercise performed at a higher intensity level. The cardio zone is between 70 percent and 85 percent of maximum heart rate, and at this intensity, a larger percentage of calories burned come from carbohydrate stores rather than the fat stores. Although the fat-burning zone utilizes a larger percentage of fat as fuel compared to the cardio zone, it does not burn as many calories, and for overall fat loss what matters most is the difference between the number of calories you expend and the number of calories you consume. Exercising at this intensity level for an extended period will burn more calories than exercising at a lower intensity. Higher-intensity exercise also has a more significant effect on keeping your metabolism elevated after your workout, which also adds a few more calories to your deficit.

So, with all of this said, the most ideal choice is vary your workouts with both fat-burning and cardio zone routines. Keep your body guessing, and you will always make improvements. Read below for a guide on determining your target heart rate zone!


Maximum heart rate is determined by subtracting 220 from your age. From that, you can determine your target heart rate zone by multiplying your maximum heart by the percentage you wish to be in. For example, a 30-year-old woman who wishes to be in the fat-burning zone would calculate her MHR like this: 220 – 30 = 190 maximum heart rate. Multiply 190 by 55 percent to get 104 beats per minute; multiply 190 by 72 percent to get 137 BPM. The target heart rate for a 30-year-old woman in the fat-burning zone is 104 to 137