the science behind
The goals of the High Intensity Strength Circuit and High Intensity Speed Circuit are to maximize the minimum by getting in a quick, powerful workout that burns body fat and builds muscle not only during the workout but long after, increases overall wellness, and has a slew of health benefits. While the High Intensity Strength Circuit is focused on strength and hypertrophy (muscle growth) and the High Intensity Speed Circuit is focused on agility and explosiveness, the research shows the health benefits of each are essentially the same. If you don’t understand everything in the first read through, that’s completely fine--we understand that this stuff is pretty dense. We’re distilling it down to need to know info, but still providing plenty of technical details for you science buffs out there.
As an overview, doing the High Intensity Workouts will enable you to become more fit through metabolic conditioning (increasing your metabolism and having it run more efficiently) and become more toned and cut (muscle definition will show.) By working at your maximum effort, your body responds with direct physical adaptations. You’re putting your body under an enormous amount of acute stress--increasing the stress hormones adrenaline and cortisol, increasing heart rate, increasing blood pressure, and fatiguing and breaking down muscle tissue. In order to cope with all these stressors your body changes and adapts so that the next time these come around you’ll be better prepared to handle them. Your body adapts by building lean muscle mass, increasing cardiovascular fitness, decreasing inflammation, decreasing risk for major modern disease, and burning off body fat. And that’s just the start of it! Best of all, it happens in under an hour total a week.
This is the Science Behind people and we’re going to dig a little deep so strap in and hang on for the ride...
Global Metabolic Conditioning: (An)Aerobic Capacity
High Intensity Exercise is, for all intents and purposes, anaerobic training. Anaerobic training doesn’t use oxygen to get the job done, whereas aerobic training does use oxygen. Examples of anaerobic training include sprinting or weightlifting; examples of aerobic training include activities like jogging or long swims.
Now, High Intensity Exercise directly increases citrate synthase, which is an enzyme in the mitochondria (“the powerhouse of the cells in your body”) that indicates the power of muscle tissue to use oxygen. So although High Intensity Exercise (anaerobic training) doesn’t use oxygen, it inherently increases aerobic capacity by increasing citrate synthase (study). What’s even more interesting is that High Intensity Exercise has been shown to cause the same increases in how quickly muscles can absorb oxygen as Low Intensity Exercise! (study)
At this point you might be thinking “WHAT? This is counterintuitive to everything I’ve been taught!” The question is why is conventional wisdom still under the belief that Low Intensity Exercise is better for increasing cardiovascular fitness versus High Intensity Exercise? How did this old school thought paradigm even come about? Well, in the 1970s, Dr. Kenneth Cooper tried to isolate the anaerobic and aerobic metabolic pathways in the body by coining the term “aerobics.” The logic was one of inference, where aerobic (an energy pathway) was synonymous with aerobics (a “new” form of exercise) which was synonymous with cardiovascular training (an actual form of exercise.) This is why nowadays people will do “aerobics.”
The problem with Cooper’s was inherent because he wanted to isolated the anaerobic and aerobic pathways, which is not possible. Energy always moves from the anaerobic system through the aerobic system. So in addition to the fact that High Intensity Exercise increases cardiovascular capacity more than Low Intensity Exercise, we now know that the anaerobic pathway precedes the aerobic pathway and the two can’t be separated. Cooper, again the one who coined the term “aerobics” and therefore the one who the Low Intensity Exercise paradigm springs from, even realized that intensity level matters stating: “you achieve a greater training effect if you put more effort into your exercise.”
Up to this point, we know for a fact that anaerobic training increases aerobic capacity via metabolic adaptations. These adaptations occur within the cell which is supported by the cardiovascular system. But how does this really happen? Well, time to dive a bit deeper…
During anaerobic work, pyruvate is created outside of the cell at a faster rate than it can be used in the aerobic system. The glycolytic pathway (outside the cell) will always be able to make pyruvate faster than the krebs cycle (inside the cell) can use it. The pyruvate accumulates and is converted by lactate dehydrogenase to lactic acid, causing lactic acidosis--that burning feeling you get in your thighs or chest and arms when going up a flight of stairs really fast or doing a ton of pushups. So we got a bunch of lactate accumulating outside of the cell because its predecessor pyruvate can’t get processed quickly enough into the cell.
At this point, to process the lactate it’s converted back to pyruvate, which can then be processed aerobically into the cell. Therefore, during recovery from High Intensity Exercise (once pyruvate production has stopped), the aerobic system is stimulated to an equal or greater degree than conventional Low Intensity Exercise! All the benefits to the cardiovascular system that happen aerobically occur during recovery from High Intensity anaerobic work! Ultimately, if you do a brief amount of really hard work (High Intensity Exercise) you’ll get more benefit than if you take a ton of time to do really easy work (Low Intensity Exercise)--and it’s done while you’re on the floor, gasping for air, as your body and brain try to figure out what the hell just happened!
Global Metabolic Conditioning: Fatty Acids and Glycogen
When you’re put your body under severe muscular exertion or emergency situations, ie, the High Intensity Strength and High Intensity Power workouts, adrenaline and glucagon stimulate triacylglycerol (adipocytes/fat cells) mobilization by activating an enzyme called hormone-sensitive lipase (HSL.) HSL discharges fatty acids into the blood, where they bind to albumin. This transports the fatty acids to the muscles, where they undergo beta-oxidation to form 35 ATP. ATP (adenosine triphosphate) is a molecule that transports energy within cells for metabolism; it’s basically a way of moving energy around. As a second benefit, glycerol (an intermediate step in this process) can be sent to the liver where it’s then converted to glucose; here it can can oxidize to form 96 ATP.
Also, glycogenolysis (breakdown of glycogen for energy) occurs during emergencies (your body sees High Intensity Exercise as an emergency!) We have glycogen (strings of glucose--or sugar said simply) molecules stored within our muscles (about 220 grams for a typical male adult) which gets grabbed on site at the muscle and is quickly used for energy within the particular cell. In other words, during High Intensity Exercise we have three ways energy gets used: HSL mobilizes fatty acids to muscles for energy, glycerol gets converted to glucose where it’s used in the liver for energy, and glycogen is pulled out of the muscle for energy.
These are important because all three only happen concurrently during High Intensity Exercise. Your body sees High Intensity Exercise as an emergency situation and pulls all the resources it has to survive. If you’re doing Low Intensity Exercise you’re not able to use all this energy.
Global Health Effects: Glycogen Storage, Blood Cholesterol, and Inflammation
As we said previously, huge amounts of glycogen molecules are grabbed from the muscle cell during High Intensity Exercise. Because the body works to find balance and homeostasis, insulin receptors on the muscle cell surface become more sensitive--which is a very good thing! Insulin is what your body uses to regulate blood sugar levels and deliver nutrients, but when your muscles are depleted of glycogen (carbohydrates/sugar) insulin sensitivity increases. The opposite can be found in type 2 diabetes, where the glycogen stores are full (remember the max amount is about 220 grams for a typical adult male) and blood sugar is consistently elevated. In this situation the body becomes insulin resistant, which is why many type 2 diabetics have to inject insulin, particularly after high sugar meals.
It’s awesome that glycogen stores are drained during High Intensity Exercise because any excess glucose will get stored in those muscles cells instead of being converted to body fat (see below.) On the other hand, when full glycogen stores are combined with high carbohydrate intake, the production of fatty acids in the liver is stimulated, increasing the amount of very low-density lipoprotein (more commonly known as vLDL cholesterol.) LDL cholesterol is commonly known as “bad cholesterol”--check out the Science Behind the Meal Philosophy for more info on this. When Low Intensity Exercise is used, circulating glucose is stored as body fat and the muscle cell walls lose their sensitivity to insulin! These cell walls are inflamed by the high levels of insulin the body’s produced to combat high levels of glucose circulating. And as mentioned in the Science Behind the Meal Philosophy, inflammation is the root of many of the major modern diseases.
Oxidation and Inflammation
Digging a bit deeper, aerobic metabolism inherently requires oxidation (because it’s using oxygen, duh!), thereby producing more inflammatory free radicals. Oxidation innately increases inflammation (yikes!). Also Low Intensity Exercise only targets fat for metabolization--and doesn’t target glycogen stores. This decreases insulin sensitivity, thereby increasing the likelihood of developing type 2 diabetes.
The Synergy of Hormone Sensitive Lipase & Carbohydrate Intake
As we previously discussed, when glycogen is mobilized during High Intensity Exercise, hormone sensitive lipase is activated, allowing mobilization of adipocytes/fat cells to be used for energy. But (and this is a big but) if insulin levels are high, Hormone Sensitive Lipase is inhibited and it can’t even be used! And how are insulin levels elevated? Well, when there is high carbohydrate intake (refer to the Science Behind the Meal Philosophy for more info.) Conversely though, lower insulin levels do allow Hormone Sensitive Lipase to be activated. As you can see, it’s a synergistic relationship between diet and exercise: a low carbohydrate diet coupled with High Intensity Exercise is a double whammy for fat burning when it comes to being able to use our friend hormone sensitive lipase.
The Role of Muscle
So now that we know why and how High Intensity Exercise and anaerobic conditioning is superior to Low Intensity Exercise and aerobic conditioning for cardiovascular fitness, global metabolic conditioning and overall health, let’s look at muscle’s role in all this.
The body’s response to High Intensity Exercise employing extreme muscular exertion is to synthesize (build/create) more muscle, which is metabolically active. When we say muscle is metabolically active, we mean that it requires considerable amounts of energy to not only create it but to maintain it as well. And this energy to create it will come from either external energy (foodstuffs) or internal energy (fat stores). Also, more muscle produces more space for glucose, and more space for glucose means insulin sensitivity is increased! As mentioned before we want increased insulin sensitivity so we can get nutrients delivered, decrease overall inflammation in our bodies, and greatly decrease our risk for type 2 diabetes.
The High Intensity Strength and High Intensity Power workouts have been uniquely designed to activate the fast fatiguing muscle fibers (commonly misnomered as fast twitch muscle fibers.) When you see a basketball player dunk or see a sprint run a 100 m dash, they are recruiting they’re fast fatiguing muscle fibers. Although they fatigue the fastest, they also produce the most amount of power. The fast fatiguing muscle fibers are also the largest muscle fibers in our bodies and in turn also cause the greatest amount of demand on the body. Although they are fast fatiguing, they take the longest to recover. This is why High Intensity Exercise can only be carried out for brief periods; conversely, Low Intensity Exercise is limitless in duration for all intents and purposes.
When we taxing the fast fatiguing fibers, insulin sensitivity has the maximal chance of taking effect. This is because, as we said, these are the largest muscle fibers, which means more room for glucose storage and glucose depletion! Also to synthesize and maintain fast fatiguing muscle fibers is more metabolically taxing than to do the same for slow fatiguing muscle fibers, thereby burning fat stores for energy. To show just how metabolically taxing this is, a study by Tufts University indicated that the body burns at least 35 calories/day for every pound of lean muscle! (study) In pretty stark contrast, fat requires about 2 calories/day per pound. (study) That’s about 1650% (aka a LOT!) more calories to maintain muscle versus body fat, and as we know, the calories to maintain muscle can come from body fat! What’s not to love?
Dr. Wayne Wescott conducted research where he compared the unique protocol used in the High Intensity Strength workout with standard conventional repetition speed resistance training. He demonstrated about a 50% better strength gain in the group using the unique protocol of slower repetitions versus the conventional group. The study was repeated and same results were found! (study). A recent 2014 study by Fisher showed very similar results in older populations of individuals. This protocol was a 10 seconds concentric movement (producing force), 10 seconds eccentric (releasing resistance), 1 to 2 times a week. Sound familiar people? (study).
Taking a look at muscle and bone, the mechanism for increased bone density was once thought to be caused by mechanical stress and high impact loading. This meant that you had to have high impact loading such as jumping (where you land with an impact upwards of 6x your body weight) in order to increase your bone density. The clear paradox in this is that in order to attempt to prevent bone fractures you’d have to do something that inherently increases risk for bone fractures (umm... WTF?). Thankfully, this is an old paradigm that has since been questioned amid the latest scientific research. Now, it seems there are a host of myokines that help the communication between muscle and bone. This results in bone density improvements without consideration for mechanical stress/strain (study). So what does mean exactly? Building muscle helps to increase the density of your bones!
Bringing It All Together
So there you have it! Hard, intense work for brief periods of time will get you not only the body you want, but the level of health and fitness you’ve been looking for all along. If this was a bit too dense on the first go round, just review it again. Remember, understanding why you’re doing something can many times be just as important or more important than what you’re actually doing! And doing the High Intensity Strength and High Intensity Speed workouts are a great thing to do. Now go out there and kick some butt!