The health and fitness benefits of High Intensity Interval Training are well researched and established. Below we learn why from a fuel perspective.
From Jeff Volek PhD and Dr Stephen Phinney MD’s book ‘The Art and Science of Low Carbohydrate Living’ we read, “The predominant fuel preferred by your heart when you are not exercising is fat. The heart rarely uses much glucose, with the only exception being during a heart attack when a vessel is plugged and the oxygen supply to that part of the muscle is cut off or severely reduced. In that case, the small amount of glycogen in heart muscle is used anaerobically to make lactate.
And here’s one more bit of heresy about lactate. During exercise, a healthy and well-perfused heart actually takes up lactate from the circulation and burns it to CO2 and water. Lactate is preferred by heart muscle cells over glucose, and during endurance exercise, lactate can provide as much as 50% of your heart’s energy need.”
Lactate is produced in the working muscles during more intense exercise and is immediately used as fuel in the heart. This lactate not used by the heart is recycled by the liver to produce more glucose (blood sugar). That glucose is again used by the working muscle. This recycling process is called the Cori cycle.
Because the heart is using lactate during more intense exercise it becomes “more adept” i.e. stronger, and better able to function. A stronger heart and working muscles are healthier overall.
Caution: Before undertaking high intensity interval training if you’ve had any health issues please seek the advice of a licensed health care practitioner before starting any exercise program.