Fuel needed to produce energy to support your exercise training depend very much on the intensity of your training. At moderate intensity training, fatty acids are used by the body as the source of fuel for energy. As the intensity increases to high intensity training, the body will start to use up sugar for fuel. The graph below obtained using Polar Wearable Chest Strap measured heart rate during a training and found that almost 50% of the time, moderate intensity exercise was achieved, evident by FAT (fuel from fat) being used for almost 22 mins and 50% of the training is at high intensity , FAT (Fuel from sugar) being used for almost 22 mins.
How do you determine what intensity of training you are currently at? There is a formula to this and there are 2 important information that you need. First is your current age and second is your resting pulse rate. The latter can be measured by placing your fingers on you wrist near the base of your thumb first thing in the morning when you wake up for 10 seconds. Then multiple the pulse rate with 6. That will give you your resting pulse rate per minute. Measuring resting heart rate at times other than your first waking up time may not be accurate as you have already been physically active, resulting in a falsely higher resting pulse rate reading.
The formula is listed below:
220 – (Age) – (Resting pulse rate) = Maximum heart rate (MHR)
Minimum heart rate for moderate intensity = [40/100 X MHR ] + resting pulse rate
Maximum heart rate for moderate intensity = [60/100 X MHR ] + resting pulse rate
Minimum heart rate for high intensity training = [80/100 X MHR ] + resting pulse rate
Therefore, for someone [Mdm LA] who is 30 years old with a resting pulse rate of 68, the calculation will be as below:
Minimum heart rate for moderate intensity = [40/100 x 122] + 68 = 117
Maximum heart rate for moderate intensity = [60/100 x 122] + 68 = 141
Minimum heart rate for high intensity training = [80/100 x 122] +68 = 166
Therefore, for fuel burning, Madam LA needs to maintain her exercise intensity with heart rate between 117 to 141 beats per minute. Training intensity above the heart rate of 166 will results in glucose be used for fuel.