The key to fat loss and fitness gains is varying the intensity throughout your program. To better understand body mechanic, your body has three different energy supply systems that respond differently to different training intensities. Each energy system burns fuel at different rates, but they all have a common goal – break fats and carbohydrates down to produce ATP.
ATP (Adenosine Triphosphate)
Muscles need a constant supply of energy to help the body move. If there is a deficit of ATP we come to a halt. ATP is a high energy molecule and it is the only molecule that the body recognize.
We have a small limited amount of ATP available in our ATP pool which is constantly varies throughout the day. When we need to move faster or work harder for longer periods our body then needs more ATP than what the pool can supply.
Your body’s energy systems then must start breaking down fat and carbohydrate to keep a constant supply of ATP going. All three systems work simultaneously. The intensity of our workouts will govern which energy system is predominant at any one time.
You can better understand the energy system by using the analogy of gears in a car to better understand burning of fat and getting fit.
1st Gear (ATP-PC System)
When we move from a resting state our muscles instantly need ATP to contract. We set off in first gear for the first few seconds as our muscles draw ATP from its own pool. This system is also referred to as our anaerobic system as it is instant without oxygen.
First gear is used for fast powerful explosive movements such as a 100 m sprint. Such events deplete the ATP pool within 10 to 12 seconds of all out explosive exertion. Once the ATP pool has been depleted you have to reduce the intensity and drop into second or third gear.
Breaking down of energy from food and body fat begins in second & third gear. First gear uses the most calories of all the gears but can only lasts for a few seconds.
2nd Gear (Glycolytic System)
Training at this level takes place at a very high intensity which could last more than 15 seconds, but no longer that a couple of minutes, you are in second gear. At this intense level our body becomes very fatigued, produces lots of lactic acid, and our muscle demand far more oxygen than we can deliver which causes a massive oxygen depletion.
Slow down the intensity and move into third gear which is a lighter pace. Let the lactic acid subside and draw in lots of oxygen to clear the oxygen debt by breathing heavily.
In second gear the body breaks down lots of carbohydrate and fat to produce ATP to fuel the working muscles. Second gear is where the magic happens, this is where all our results come from.
3rd Gear (Oxidative System)
In the third gear our aerobic system relies on oxygen with break down of fat and carbohydrate to obtain ATP. In this gear we can keep going for very long periods of time such as running long distance. This intensity does not take you towards lactate threshold nor does it create a large oxygen depletion.
Body fat is the predominant fuel that is burned in third gear.
It is good to move up to second gear and use third gear to recover after you have done a minute. If you are new to exercise it is good to build up some endurance by training in third gear for up to 20 minutes.