Picture this: You are 5’6″ tall and weigh 40 pounds more than you should. You desperately need to lose weight, but every time you walk up a flight of stairs or try jogging around the block, you gasp for air. Exerting yourself to burn calories extinguishes the flame of desire. But you persist. Before long something hurts. Your knee or maybe your hip. Now you’re in trouble. What do you do?
How will you ever lose the weight?
Everyday millions of Americans climb onto a treadmill, a stair stepper or bike and log countless hours per week in a futile effort to burn fat. They labor under the illusion that long duration, low intensity exercise, the “aerobic zone”, is the best way to burn fat.
But is it?
Truth is the key to burning fat is a combination of intensity and duration of the exercise. Short bursts lasting up to 15 seconds followed by a rest period of up to 45 seconds has been proven to mobilize fat for energy more efficiently than longer periods of exercise. Here’s how it works.
Let’s examine what happens when you, at 300lbs, go for a 30 minute walk.
When you begin exercising, the body looks for a quick source of energy and finds it in the form of Adenosine TriPhosphate or better known as ATP. ATP provides energy for about 5 seconds. As you continue walking your ATP levels fall and your body begins burning carbohydrate (glycogen) stored in the muscles. Glycogen is easier to burn than fat because glycogen does not require oxygen to produce energy. As you continue using glycogen, you produce lactate commonly known as lactic acid. Lactic acid is carried through the blood stream to the liver where it is converted back to glycogen. As long as the rate of lactate production and glycogen reassembly is the same, you don’t feel fatigued. But, if you continue the glycogen burning, the lactate levels will rise causing you to breath harder, eventually slow your walk and finally stop.
The more fit you are, the sooner you will access fat stores for energy. The sequence of energy use is always the same for every person no matter your weight: ATP, Glycogen, Fat. The difference is in how much fat you burn. The 300lb person carrying a high degree of body fat has difficulty burning fat because the intensity and duration of walking is too great. Walking has become an anaerobic event which means there is an oxygen deficit causing you to burn glycogen. And the more you do it, the better you become at NOT burning fat. You walk your way into gaining weight.
So, how do you change this?
You have two choices.
Low intensity, long duration exercise or high intensity, short duration exercise. A low intensity exercise is one which requires your heart to beat at 65-70% of its maximum (to calculate your max heart rate, use this formula: 208 – (AGE*.70)). For the 300 lb person, walking elevates your heart rate too fast and too soon leading to an anaerobic state. Walking is too intense of an exercise for someone in this condition.
Interval training however is a possibility. Short intervals of high intensity exercise (10-15 seconds) followed by low intensity effort accesses fat and reduces the amount of glycogen you use. The result is lower levels of lactate and higher levels of fat burning. High intensity, short duration exercise burns fat because of a special protein in the muscle cell called Myoglobin. Myoglobin holds oxygen and releases it during the intense, brief effort. It carries enough oxygen for about 15 seconds of exercise and then reloads. Fat needs oxygen to burn so as long as oxygen is available, you will use more fat than other sources for energy. But if the oxygen level drops, your body shifts to sources which do not require oxygen like glycogen. If the duration goes beyond 15 seconds, Myoglobin runs out of oxygen and you begin burning more glycogen.
The best choice then would be any of the following:
Your body will continue to burn fat for another 24 hours after the exercise session which is huge return on your investment when you consider that with a long, slow distance exercise, your use fat as a fuel source only if the intensity of the exercise is correct and only during the exercise.
High Intensity Interval Training is often used interchangeably with “Tabata Training”.
But they’re not the same thing.
In 1996, Dr. Izumi Tabata and colleagues studied two forms of exercise to determine the effect on anaerobic capacity and VO2 Max. ((http://www.ncbi.nlm.nih.gov/pubmed/8897392))
In the study, seven subjects performed 20 seconds of maximal effort on a bike (maximal in this case was 170% of Max VO2) followed by 10 seconds of rest. The subjects repeated this for a total of eight sets.
The subjects improved both their aerobic and anaerobic capacity as a result of the interval training. But Dr. Tabata never studied the effect on body fat.
Since the study though, trainers, fitness “experts”, coaches and others have started using the word “Tabata” to describe almost any type of exercise that falls into the 20″ / 10″ work to rest range or is an intense, short period of work followed by rest and also suggest that this is best for “fat burning”.
Some examples:
To get the full benefit of a Tabata interval, you need a spin bike and perform 20 seconds of maximal, all-out pedaling followed by 10 seconds of rest repeated for a total of 8 cycles or four minutes (although Dr. Tabata has modified his regimen to include a rowing machine in an attempt to take the concept mainstream ). ((http://www.guardian.co.uk/lifeandstyle/2013/mar/25/tabata-harder-faster-fitter-quicker))
Pedaling all out in this case is 170& of your Max VO2.
How hard is that?
Well, at 100% of your maximum heart rate, you’ll be very close to your 100% Max VO2.
In the study, the subjects were highly trained athletes who could tolerate 170% MaxVO2. I’ve done Tabata intervals on a spin bike and I can tell you that when you finish, you feel like you never want to do that again. Ever. If you don’t feel that way, then you haven’t performed the Tabata interval properly.
My advice is to start with a more “generic” version of the Tabata – the High Intensity Interval. This allows you to adjust the intensity, the work-rest ratios, and your durations to better suit your abilities. As your fitness improves, you may want to give the Tabata interval a shot.
Have you performed Tabata Intervals? What was your experience?
References:
King, J., Panton, L., Broeder, C., Browder, K., Quindry, J., & Rhea, L. (2001). A comparison of high intensity vs. low intensity exercise on body composition in overweight women. Medicine and Science in Sports and Exercise ,33 , A2421
Treuth, M.S., Hunter, G.R., & Williams, M. (1996). Effects of exercise intensity on 24-h energy expenditure and substrate oxidation. Medicine and Science in Sports and Exercise ,28 , 1138-1143
Christmass, M.A., Dawson, B., & Arthur, P.G. (1999). Effect of work and recovery duration on skeletal muscle oxygenation and fuel use during sustained intermittent exercise. European Journal of Applied Physiology ,80 , 436-447
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