Last week I was at a spin class, and the instructor had us do a steady ride for a song or two, and said we’d be burning more calories in this aerobic pace because we were in the fat burning zone. Then she said we should come to her endurance ride because it would be 90 minutes in the fat burning zone. I was thinking to myself, “Wait what? Is the fat burning zone still a thing?” I haven’t heard that terminology in forever, so I started doing some research…aka Googling
From what I remembered, the fat burning zone was maintain your heart rate at a certain rate in order to burn the most fat/calories. So why is this the case, supposedly? Here’s a great explanation from Active:
The fat-burning zone is a concept that the body burns a greater amount of fat at lower-intensity aerobic exercise than it does at higher intensities. Actually, the body burns a greater percentage of fat at lower intensities than at higher intensities. At lower intensities the body may burn 50 percent of the calories from fat, while at higher intensities it may only burn 35 percent. But at higher intensities you burn way more total calories—and more fat calories overall—than you do at lower intensities.
Very interesting. And that’s what I was thinking in the class. We did a lot of hill rides and sprints and in my mind, that probably burns more calories overall than a steady pace. Furthermore, us runners know that the more you do something at a certain pace/rate, the more your body adapts. If you’re in the aerobic zone for every workout for months, eventually you will plateau. Speaking of plateau, I wrote about a few ways to beat that pesky plateau a while ago.
Let’s also talk about the afterburn effect. You may have read in plenty of fitness magazines that the reason HIIT (high intensity interval training) is so beneficial is because of the afterburn. For hours after you’re done exercising, your body continues to burn calories, whereas after aerobic exercises, there isn’t much of an afterburn. In a study done by the University of Maine, “A low intensity exercise group cycled at a steady rate of 3.5 minutes. The higher intensity exercise group required three 15 second sprints as fast as the subjects could run.”
What were the results?
The cycling group burned 29 calories vs. 4 calories for the sprinting group during the exercise. But when you take into account the calories burned after exercise, or the afterburn effect, the numbers look much different – 39 calories burned for the cycling group vs. 65 calories burned for the sprinting group. A surprising 95% of the total calorie burn occurred after the sprinting exercise!2 Keep in mind the cycling group exercised for almost 5x longer than the sprint group (3.5 minutes vs. 45 seconds).
I’ll admit, sometimes when I do a quick hill sprint session on the treadmill and I’m done in 15-20 minutes, I feel like I should keep exercising. But it’s clear that HIIT training really does have more “bang for your buck.” Why slog along on a treadmill for hours (okay maybe that’s an exaggeration) when you could do circuit training or HIIT and be done in 20-30 minutes (and reap the same benefits if not better)?
Obviously, this all doesn’t relate to those of us who are training for a long distance race. That is always the conundrum I have. I want to burn more fat and get leaner, but I’m be training for a half marathon or a marathon, so long, steady state cardio is my life at the moment, other than track workout or tempo days. Though I have started doing circuit training for strength workouts that are high intensity and last 30 minutes. I’ve loved it so far, and it’s a good change of pace from my usual lifting routine. Here’s an example of a workout I do.
Have you heard the term “fat burning zone” used recently?
What do you think of it vs. HIIT?
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