There is no “fat-burning zone”. Instead, surprise your body with HIIT cardio.
One of the most deep-seated and fiercely argued tenets of cardio work is that in order to burn fat, you should always be working in the “fat-burning zone.” If you’ve ever been on a cardio machine at a health club, you’ve seen those nifty little guides that relay the supposed effects of different heart rate zones. With words such as “Maximum Fat Burn Zone” plastered all over lower heart rates, it’s no wonder that we’ve all been seduced into thinking that the only way to burn that stubborn fat off is to keep our heart rates low and steady.
Consistently working out at a low intensity can actually train your body to store fat. You read that correctly. If you consistently perform low-intensity exercise (that is, at a low heart rate), your body will adapt by beginning to store fat so that it can complete the next bout of exercise more effectively. This scenario is called “metabolic efficiency,” and it’s the ultimate catch-22 of exercising.
Metabolic confusion is the opposite of metabolic efficiency. By regularly switching up the duration, intensity, and type of exercise you’re doing, you can keep your metabolism on its toes. When your body doesn’t know what type of workout is coming next, it doesn’t have the opportunity to burn fewer calories in order to complete the task at hand. Instead, your body is forced to react to the ever-changing stimuli of new workouts and therefore will burn a higher amount of calories. Studies show that high-intensity interval training (HIIT) is the most effective form of exercise to achieve metabolic confusion and burn abdominal visceral fat.
What constitutes a HIIT workout? Any activity that spikes your heart rate up to about 70 percent of its maximum for a short period of time, then allows you to recover at a lower heart rate, then spikes your heart rate up again. If you were to graph your heart rate, it might look a rising series of peaks and valleys.
The effectiveness of HIIT workouts is because of a phenomenon known as excess postexercise oxygen consumption (EPOC). After a workout, your body will continue to consume oxygen for a certain amount of time in order to bring your body back into its resting state. The more oxygen your body consumes, and the longer it does this, the more calories you will burn. As you know, more calories burned equals more pounds lost, which equals a tighter tummy for you. The key letter in the acronym is “P” for postexercise. This means that not only are you burning fat during your workout but you will also continue to burn calories and fat long after your workout has ended.
The only caveat about HIIT is that more is not always better. There is a limit, however, to how much stress the body can handle; if you tax your body too often and too intensely, you will pass the threshold of good stress and cross over into the bad stress zone, causing a release of that dreaded cortisol, which can cause your body to store fat. In order to avoid this scenario, it’s important to give your body time to recover between HIIT workouts, ideally 48 hours. For this reason, the Core Envy program spaces out HIIT workouts throughout the week.
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Allison Westfahl’s Core Envy will tone and sculpt your abs, back, stomach, and sides—and build a strong, sexy core you’ll love showing off. Her Core Envy program solves the problems other abs programs ignore with a three-part approach to slim down and tone up. You’ll clean up your diet, fire up your metabolism, and tighten up all the muscles of your core without a gym or equipment. In just three weeks, you’ll start seeing results.