Would you like to find the most efficient way to get in the best shape of your life? Look no further than High Intensity Interval Training (HIIT). I won’t promise it’s easy, but if done right, it gets results fast. High intensity interval training is when you alternate between very high intensity exercise and lower intensity exercise or rest periods.
It’s physiologically impossible to sustain maximal intensities during exercise for an extended amount of time. This is because of how our bodies use fuel. The body needs energy for cellular function. ATP is the source of energy the body uses. We have two energy systems, aerobic and anaerobic. Both have their own advantages and disadvantages. HIIT uses a mix of aerobic and anaerobic energy pathways.
In exercises where there is a readily available source of oxygen, we produce ATP using fat and carbohydrates. Lower intensity work uses more fat. As intensity increases, a higher percentage of carbohydrates is used. The aerobic system produces fuel for sustained exercise. The aerobic threshold is the point where the body moves from aerobic energy supplies to anaerobic. As you increase your fitness, particularly when you work at high intensities, you improve your ability to use your aerobic energy system at higher intensities, allowing you to go faster longer.
As exercise intensity increases we lose the ability to use oxygen for fuel and turn to our anaerobic energy system. The anaerobic energy system has two energy sources: the ATP-PC system and the Glycolysis system. The ATP - PC System uses creatine phosphate (phosphocreatine) to create a very quick source of ATP. This system provides us with 10 to 20 seconds of energy at all-out exertion like in a 100 yard sprint.
The Glycolysis System converts glucose to ATP without using oxygen and produces lactic acid as a by-product. It provides energy for intense exercise of between 1 and 3 minutes duration. This system provides the kick at the end of a mile race. If you have been a couch potato you might even consider throwing up, thanks to the change in blood pH levels.
As a general rule, duration is inversely related to intensity. You can go longer if you don’t train as hard. Most effective HIIT programs will last a maximum of 30 minutes, including a proper warm up. One of the most famous studies of HIIT is known as the Tabata study. In this study, subjects performed intense intervals of 20 seconds alternated with 10 seconds of relaxed recovery exercise, for a total of 8 intervals, or 4 minutes. At the end of the study, participants showed a 28% increase in anaerobic capacity along with a 14% increase in aerobic capacity.
That’s pretty impressive for a 4 minute workout!
Research shows that short, intense cardio workouts burn off more fat, and the shorter time means that you also spare more muscle. According to the National Strength and Conditioning Association (NSCA), anabolic, muscle-building hormones like testosterone are maximized in about a 30-minute high-intensity workout window. It is at about the 45-minute mark that anabolic hormones begin to fall as their catabolic counterparts, mainly cortisol, simultaneously begin to rise.
High intensity interval training has become extremely popular in the past few years and has been proven effective in improving athletic performance and enhancing weight loss. One of the greatest fat loss benefits of HIIT is due to greater excess post oxygen consumption (EPOC). This ‘after burn’ contributes to the total amount of calories that are burned with a bout of exercise. The higher the intensity, the more caloric expenditure is needed after the exercise to return the body to normal. HIIT will continually burn more calories hours after the session has ended.
HIIT also improves many health risk factors.
Many people avoid high intensity exercise because of the fear that they will get injured or that it will be too hard. In reality, HIIT is safe if an individual’s conditioning is gradually built up and the joints are appropriately strengthened to tolerate the stresses. Make sure the HIIT program you do is based on science, and designed from effective movement patterns with certified coaches. The program should have been tried and tested for safety and results. If you have any health concerns, check with your doctor before trying HIIT.
Perry Buchanan, owner of PT Gym, is certified as Health Fitness Specialist through the American College of Sports Medicine, and Fitness Nutrition Specialist through the National Academy of Sports Medicine. He has been in the fitness industry for more than 35 years.