HIIT Research

Based on research findings, the key is in the balance of the three sources of fuel available to our muscles: Glucose, Adenosine Triphosphate (ATP) and Fatty acids. Fatty acids are stored throughout the body as fat, whereas glucose (stored in the form of glycogen) and ATP are found in the muscle itself. Which source of fuel is primarily utilised depends on the intensity of the exercise and the heart rate that exercise requires. During a steady state of exercise, such as walking, the heart isn’t required to beat above 65-70% of your maximum heart rate (MHR).

At this rate, it is primarily the fat stores which are accessed. Sound like the solution? Not quite. As the name suggests, High Intensity Interval Training requires your heart to work at varying intervals/levels. The idea is to exercise at a high intensity (on-time) for 8-30 seconds and taper off to low-moderate intensity (off-time) for up to a minute, depending on your fitness goals. During on-time, your heart must work at between 70-90% MHR and return to less than 70% during off-time. At between 70-90% MHR, the glycogen and ATP stores within the muscle will be required as a source of energy. However, both ATP and glycogen will provide energy to the muscle for only a limited period of time, meaning your heart rate will need to drop to below 70% MHR during off-time to allow the muscles to search for a means of replenishing such stores.

Enter fat burning process number two.
Once ATP and glycogen are depleted, and your heart rate is reduced to around 70% MHR, your body will break down your fat stores and convert it into glycogen and ATP. In other words, not only will you be burning fat during off-time, but after a short burst of high intensity exercise, your body will need to break down fat again at an even greater rate to replenish ATP and glycogen stores to the muscle. Moreover, this replenishing process will continue for 24-48 hours after the exercise is completed! What makes it even more exciting is that, by continuing the Pilates muscle building process in parallel, the fat burning potential is enhanced even more. The greater the muscle mass, the greater the number of outlets for ATP and glycogen release, the more fat burning required to replenish ATP and glycogen stores! So how long does this form of exercise need to last?

MD Health is proposing a mere 20 minutes (plus 5 minutes warm up and 5 minutes cool down) twice a week to get the best results. That’s a 40 minute fat burning process that would otherwise require at least 2-4 hours of walking to achieve similar results - a fat burning process up to 4 times more efficient.