
If your body was a car the muscles would be the engine, so to burn fat you want to build the biggest engine possible and race that engine as hard as it can go. I love training myself like this, and I train a lot of my clients like this (photo of Jamie and Betsy above). In this blog I explore "The Fat Burning Zone" and the science of how High Intensity Interval Training turns your body into a fat burning machine.
DURING your workouts your MUSCLES (importance of resistance training) look for fuel from mainly Carbs and Fats in the bloodstream or within the muscle itself. Protein is mainly used for fuel during the depleted state, post workout.
Energy from Bloodstream: Carbs are in the form of Glucose, Fat is released from stores into bloodstream (liposys).
Energy from within the Muscle: Carbs are in the form of Glycogen, Fat in the Muscle is called Triglyceride.
During your workout your MUSCLES use a combo of Fats and Carbs for energy based on the DURATION and INTENSITY of your workout. The "Fat Burning Zone," is based on the science that fats require more oxygen to be used as fuel. Fat Burning Zone theory is low intensity, more oxygen, fat burning...going along with this theory still high intensity, less oxygen, more Carbs used for fuel. The low intensity part is true but the high intensity part is a little deceiving. As intensity increases, more fat is burned just in a lower percentage to the contribution of Carbs being used as fuel. I believe in the science of what the fat burning zone is (fat burning occurs when oxygen is available), but I don't believe that a low intensity workout in the fat burning zone is efficient for optimal fat loss. This is explained in 2 parts:
Part 1:
Low Intensity: Fat & Carbs in blood stream is primary source of Fuel
Moderate Intensity: Triglyceride (Fat) in the Muscle is primary Fuel source
High Intensity: Glycogen (Carbs) in Muscle is primary Fuel source (more fat is burned at this intensity than at low but Carbs are primary source)
Part 2:
What happens after your workout. After you finish a session of High Intensity Interval Training your body has used up a large amount of stored energy from inside the muscle. Your muscle needs to refill these empty stores so it takes Glucose (Carbs) from the bloodstream and converts it to Glycogen (carbs) in the muscle. While your body is doing this it needs energy to run itself so it takes stored fat in the body and uses that for energy. After your workout you will notice that you are breathing a little harder (EPOC, Excess Post-Exercise Oxygen Consumption), this oxygen rich environment it is optimal for your body to be burning up fat for energy (the science of the fat burning zone that I believe in).
This post workout process of refilling your muscle stores and using fat for energy can take up to 24 hours depending on how much you depleted the stores. This post exercise fat burn would not occur at low intensities because the intramuscular stores would not have been depleted. The duration and intensity of the post exercise process are directly related to the intensity and duration of your workout.
The more and more you do high intensity interval training the more and more your body becomes a fat burning machine. This goes along with my philosophy that when you focus on the work/consistency that's when the results come. Your bodies ability to convert glucose to glycogen (rather than as stored fat) increases, and the amount of stored glycogen in the muscle increases. This allows for more of a depletion during training which increases the amount of fat burn post workout. This means your body becomes more and more efficient at burning fat for fuel.......Fat Burning Machine.
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