The 20 Second Burst Exercise Experiment
What is the purpose of exercise? What exactly are you trying to accomplish in your exercise workout?
I would guess that most people have no idea why they should exercise other than they've heard that "you should exercise". So they go exercise. And I've seen some of the most bizarre activities that people call exercise. Some activities I've seen border on circus acts that range from comical to accomplished acrobatic feats. But are these really doing anything important to improve the functions of the body?
Why do people do their signature "exercise" stunts and call them exercise when in fact they risk injury, waste time, and probably worst of all, embarrass themselves for the world to watch? The feats of glory are not exercise at all.
The benefits of exercise come down to metabolic results (so noted, there are other benefits such as a sense of wellbeing, social benefits, and many others). The metabolic results of a strategic exercise program are improved heart capacity, lung capacity, and improved enzymatic capacity and hormone responses. Attempting ripped biceps or washboard abs should not be the goal. Improving performance should be. Improving health outcomes should be. Living a long, strong, and healthy life should all be goals of exercise.
So how exactly do you do this, improve your life with exercise?
Exercise = Intensity
The goal of exercise is intensity. The greater the intensity the greater the metabolic affect of exercise. The greater the body, via muscular contractions, is stressed through the intensity, the greater the response and adaptations of the metabolic systems of the body.
Short, high intensity all-out bursts of muscular contractions for a limited time, offers greater metabolic responses. On the other hand, longer, low intensity muscular activity leads to minimal metabolic response and will lead to depleting the metabolic reserves of the body. A person on mile 22 of a marathon is tapping deep into metabolic reserves to keep the body in survival. The Type I muscle fibers are near exhaustion as are many other metabolic processes.
So what's better, a short duration, high intensity workout or a long duration, low intensity workout such as seen on treadmills, stationary bikes, ellipticals, and in most exercises in every fitness club in the country?
Short duration, high intensity bursts of exercise is best if you want the benefits of exercise: improved heart capacity, lung capacity, and improved enzymatic capacity and hormone responses. This may not make any sense to hard-core exercise buffs unless you understand the physiological responses that have to happen in this short time of exercise.
All long duration, low intensity exercise utilizes oxygen so these kinds of activities use aerobic metabolism to perform the necessary functions. Aerobic metabolism is homeostatic metabolism. In other words, the metabolic systems are not stressed very much to respond to and adapt to a more efficient way of functioning.
Short term, high intensity exercise by definition does not use oxygen so functions via anaerobic metabolism. It utilizes quick, although scarce supplies of energy substrates such as ATP, phosphocreatine, and glycolysis. These forms of energy have to be synthesized and the more these systems are stressed and used the more efficient they become to function during the next short term, high intensity exercise. They adapt to higher levels of function, increasing metabolic capacity levels.
A Short Summary
Long duration, low intensity exercise uses aerobic metabolism to primarily supply Type I, slow twitch muscle fibers and this process can continue for a long time. This kind of exercise does not necessarily cause the body systems to adapt and improve function but rather depletes the metabolic reserves to continue the long duration activity. Short duration, high intensity exercise utilizes anaerobic metabolism and substrates such as ATP, phosphocreatine, and glycolysis to produce energy primarily for Type II A and B, fast twitch muscle fibers for a very limited time. It is in this anaerobic metabolism when body systems are stressed to metabolic capacity that the process becomes more efficient at replenishing the substrates that make ATP, phosphocreatine, and glycolytic forms of energy. As a result, higher levels of metabolic capacity are achieved.
The question I have been working on is this; what is the shortest duration, highest intensity that offers the best physiological benefits? There must be a sweet spot of time and intensity that provides the best health benefits of exercise with the understanding that we're only going to be utilizing high intensity, short duration exercise bursts.
If you understand muscle physiology you will find that if a muscle is continuously contracted it is depleted of ATP and phosphocreatine within 8 seconds. After 8 seconds it takes two minutes of rest and recovery to restore the enzymes so that another complete contraction is possible. This is for a muscle that is continuously contracted. In a high intensity burst such as exercising all out on the Myoride exercise machine where all major muscle groups are intermittently contracted and relaxed (although quite quickly because each limb is taken through its range of motion under resistance and is concentrically contracted bi-directionally) it may take longer than 8 seconds of exercise; it may take 20 seconds to deplete these enzymes; and it may take up to 3 minutes to regenerate them. Continuing any longer than a 20 second burst of exercise or resting less than 2-3 minutes by definition makes the workout medium intensity and many of the metabolic benefits may be lost of true high intensity interval training.
The 20 Second Exercise Burst Experiment
In order that you can wrap your head around the 20 second exercise burst I want to explain how this experiment works. One of the features of the Myoride exercise machine is that each limb functions independently and each limb has an adjustable resistance setting. So, the legs (mostly hamstring, quadriceps) are set at a much higher resistance than the arms (mostly anterior deltoid, supraspinatus, infraspinatus, pectorals, latissimus, triceps, subscapularis) which are less muscle mass and have a longer distance to move the glenohumarol joint through its 180 degree range of motion than compared to the hip motion.
The ability to adjust resistance levels is very important because we want to keep velocity or cycles per minute of motion fairly constant over the 20 second burst intervals. In other words, we want to keep the cycles per minute as constant as possible beginning from the first interval, to the second, the third, and finally to the last interval. In this 20 second burst we want the speed of arm and leg cycles per minute as similar as possible from one interval to the final interval (we're counting one complete range of motion with arm starting from the anatomical position and then up into 180 degree flexion with contralateral leg from anatomical position to 110 degree flexion and then both arms and legs back into anatomical position). To make it easy we do one cycle of arm/leg motion per second (60 cycles per minute) so we’re going to have an athlete doing 20 cycles per minute which is one cycle per second for 20 seconds which is 20 cycles arm/leg motion in 20 seconds. Obviously, the first interval he does 20 at a predetermined resistance set against the legs and the arm motion. But you realize he will fatigue as the intervals continue. He will fatigue. HOWEVER, we can adjust the resistance to keep him at a 20 second per minute pace throughout the intervals! This is the beauty of the machine.
A Hypothesis in Exercise
Here's how this 20 second exercise burst experiment works. Let's take our tester, we'll call him Usain Voltage. He is on the Myoride exercise machine, laying supine, in the ready position with arms set at 3/6 resistance level and legs set at 5/6 resistance level. Let's also say we had previously determined that we can get his maximum heart rate to 200 bpm in 60 seconds with these corresponding resistance levels. Not a bad benchmark.
These resistance levels are set just enough to allow complete range of motion of both legs and arms to reach maximum heart rate in a relatively short time but not too resistant to not allow movement or fatigue too early. The sweet spot.
He's set, ready, go! All out for 20 seconds. Since Mr. Voltage is a superior athlete he gets 22 complete range of motion cycles in 20 seconds in an all-out burst. Immediately at the 20 second time we take his heart rate and find it 200 bpm and his respiration 30 breaths per minute (yes, almost superhuman!). We wait and watch him and at exactly at the 60 second mark we take his pulse which is now 98 and his respiration rate which is 22 (fantastic heart rate recovery!). Then finally, at the 120 second mark we find his pulse is now 80 and his respiration is 18. We allow him to rest one more minute (total rest = 3 minutes, enough time for him to generate sufficient ATP and phosphocreatine for his fast twitch, Type II A and B muscle fibers) before going into the second interval.
He repeats the cycle and we observe and mark the heart rate and respirations at the end of the 20 second stoppage, at the 60 second mark and at the 120 second mark. Because this is Mr. Voltage, these second set of numbers are very close, but a little higher than the first interval however, he maintained the set of 22 complete range of motion cycles in the 20 seconds, so we leave the resistance alone. Perfect!
However, even though this is superhuman Mr. Voltage, there will come a time when even he cannot keep the 22 complete range of motion cycles in the 20 seconds. But this is exactly the time that we lower the resistance in all the limbs. We want to keep the velocity the same because we want to stay in the 20 second burst mark and we want him to keep at a 22 arm/leg cycles per minute. If we go more than 20 seconds he is not by definition performing high intensity training. And if he slows his cadence less than 22 he is not gaining as great of the metabolic affects.
We continue lowering the resistance on the limbs per interval until the time that which his heart rate does not recover as the previous intervals did. His heart rate at the 60 second mark may be 112 bpm, not near 98 bpm after the first burst interval or at the 120 second third mark it may be 96 bpm instead of near the 80 bpm as it was from the first interval. Clearly his heart rate is not recovering. He is done with our experiment and his workout for the day and should not perform such cardiorespiratory workout for the next 36 hours so that he adequately recovers his metabolic reserves.
We find his sweet spot at which he can perform the entire exercise in 20 seconds at the corresponding resistance levels. At this sweet spot of time and intensity he is enhancing Type II A and B fast twitch muscle fibers and maximizing the metabolic benefits of exercise: improved heart capacity, lung capacity, and improved enzymatic capacity and hormone responses.
Over the next several weeks he will adapt to the resistance levels and we will increase them proportionally so that he is able to perform the 22 arm/leg cycles per minute in the 20 second burst but his heart rate recovery will improve as will the other physiological biometrics.
This is the 20 second exercise burst experiment and we're studying the results in hopes of proving which I have just described. We have the ability to do this, that is, to use function to find individual specifications related to biomarkers.
As for Mr. Voltage we will continue testing and improving his athletic and functional performance.