Interval Training: How Does it Burn Fat?

Interval Training: How Does it Burn Fat? (The Answer Totally Makes Sense)

Traditionally, we have been told by many so called experts that if we wanted to burn fat then we need to train in the “fat burning zone.”  According to these experts, training in the fat burning zone is the only way to burn fat when you exercise.  Well, they are right.  If you want to burn fat during your workout, do some long boring cardio in the fat burning zone.  But, if you want to triple the amount of fat that you burn, do interval training workouts.  Some basic physiology tells us how interval training burns fat long after you finish your workout.

High intensity interval training exhausts your supply of immediate carbohydrates that are stored in the muscles.  This supply is known as glycogen.  The phosphocreatine system and the glycolytic system are dependent upon glycogen stored in the muscles and the liver.

Interval training demands energy so quickly that fat stores are not able to provide energy rapidly enough to keep up with demand.  Interval training requires carbohydrate stores, glycogen to be specific, to supply the fast energy that is needed.  During your recovery period and the hours after your workout when there is plenty of oxygen present and the demand for energy quickly has slowed down, your body utilizes your fat stores to convert that fat into glycogen for the next time you workout with a high intensity.  This process of replacing the fast energy stores that you used up during your interval training workout may take hours to completely restore the glycogen stores.

So, the secret to burning fat is to not burn fat during your workout.  Burn for hours afterwards by exhausting your glycogen stores.


Interval Training – Challenge Any of the 3 Energy Systems

Interval Training – Challenge Any of the 3 Energy Systems

At the root of all training routines is the need to make the body more efficient at producing energy for your given activity, whether that is a sport, general health or life.  If you are not training specific to the energy requirements of your activity you may be wasting your time.  This article will look at what those energy systems are and give a better idea of what you may need to do to challenge those energy systems.
All of the body’s energy requirements are supplied by a chemical called ATP.  The breakdown of ATP produces an enormous amount of energy but the body can not store a large quantity of it.  It must replace the ATP that is used in a fast and efficient manner.  It does this in 3 major ways.  Though protein can be used to produce energy, it eventually ends up in one of the 3 major pathways and will not be discussed.
1.  Creatine phosphate system (PCr) – By far the fastest source of energy, the PCr system will only sustain energy requirements for a matter of seconds, not usually more that 10-15 seconds.  Think of the tip of a match, it will only burn for a few seconds but is enough to start the next system.  The PCr system is will suited for high intensity, short duration activities.  It can operate independent of oxygen supply (anaerobic).
2.  Glycolytic system – This system is somewhat like the kindling of a fire.  The glycolytic system relies on carbohydrate breakdown to “rebuild” ATP.  This carbohydrate is stored in the muscle and liver as glycogen.  The breakdown of carbohydrate can sustain energy requirements for a much longer period of time than the PCr system, up to 2 minutes according to some sources, and can also function without oxygen (anaerobic).
Two end products are produced through the glycolytic process: pyruvate and lactate.  The production of pyruvate is known as slow glycolysis and can be combined with oxygen to produce more ATP.  The production of lactate is known as fast glycolysis and can later be converted to pyruvate.
3.  Oxidative system – This may be compared to the oak log on the fire that can burn for a long period of time but takes some time to get started.  The oxidative system can use pretty much any substrate (fat, carbohydrate, protein) to rebuild ATP molecules.  It takes a much longer time but is very efficient.  The processes involved in the production are very complicated and are outside of the scope of this article.  However, this is the system that burns the fat that we want to get rid of.
Simply put, our energy systems are very similar to the building of a sustainable winter fire.  First we need a fast source of energy to ignite (a match), and slightly longer source to continue the fire (the kindling) until the logs will burn and put out the heat (the log).  To learn how to train these energy systems so that they will become more efficient go to training your energy systems.


Specific Formula to Charge Your Energy Systems

Specific Formula to Charge Your Energy Systems

In a previous article I outlined a basic model of how your body produces the ATP necessary to power your body.  That’s all great in theory but how do you apply that to your interval training workout?  Each sport or activity has different energy system requirements.  How do you tweak your interval training workout to get the most out of the energy system that dominates your sport?
Though all of the energy systems mentioned are active at any given time, depending on the intensity of the activity, one system may be more active than the others.  In this article I am going to give you a formula that you can use to specifically train the energy system that dominates the energy demands in your sport.

Training the Phosphocreatine (PCr) System
The PCr is most utilized during activities that require short bursts of high intensity.  Some examples may include weightlifting, sprinting, baseball, football, etc.  These sports require all out effort for less than 10-15 seconds.
When designing an interval training program consider the amount of time you will be exerting a maximal amount of effort and add about 5-10 seconds.  That will become the time for your work phase.  Now multiply that number by 3 to calculate the rest phase.  This is known as a 1 to 3 work to rest ratio.  So, if you are doing a work phase of 20 seconds, your rest phase will be 60 seconds.

Training the Glycolytic System
The glycolytic system is able to sustain high intensity activity for up to 3 minutes depending on the intensity of the activity.  The greater the intensity, the shorter duration that glycolysis is able to sustain the activity. Sports that may rely most heavily on the glycolytic system include soccer, basketball and hockey.  These sports require bursts of effort greater than 10 seconds with some limited rest in between intense bouts.
An interval training program should be designed according to the amount of time you will be performing at maximum intensity.  Your work to rest ratio is going to be more like 1:2.  For example, the work phase may be between 30 seconds to 90 seconds.  The rest phase would be 2x that of the work phase.  So, 30 seconds of high intensity work and 60 seconds of rest.

Training the Oxidative System
Though interval training challenges mostly the PCr and glycolytic systems, some research studies suggest that improving power output through interval training can improve endurance performance.
The oxidative system is the fat burning furnace of the body.  It takes a longer time to produce the ATP necessary to fuel the body, however, it creates about 10x more ATP than PCr and glycolysis.  That is why your body tries so hard to hang on to it.  Sports that rely on the oxidative system most heavily are those that require a light to moderate intensity over a sustained period of time greater than 3 minutes.
To use interval training for your endurance sport use a 1:1 work to rest ratio.  Your intensity should be greater than what you would normally compete at.  A good example of traditional interval training protocols for endurance sports is Fartlek training.  For example, sprint for 3-6 minutes and then slow down to a jog for the same amount of time.  Repeat for the desired number of repetitions.
Regardless of what sport or activity you participate in, you can design an interval training program that will supercharge the energy system that your body relies most heavily on.  It is important to vary your program every 3-4 weeks so that your body is constantly challenged.  Most importantly, have fun with it.  Interval training provides so many different options that you should never get bored.