Here’s a crash course in exercise physiology.
Whatever you eat, and however you exercise, your body ultimately gets its energy from a molecule called ATP, which stands for adenosine tri-phosphate. Imagine a little three-leaf clover; each leaf is a phosphate. Your body pops one of these leaves and energy is released, rendering that clover a di-phosphate (only two phosphates are left). Your metabolism looks around for something to replace that third leaf.
You may think that you get energy from calories–”fuel”–and that you burn whatever goes in when you’re exercising. While this is true in a broad sense, it is far more complicated than that. The metabolism (the rate/way in which you burn energy) is a very sophisticated and complex thing. It is dynamic, and it has different strengths and weaknesses, depending on who you are; it can also be trained and adapted, just like your body.
There are four metabolic pathways for energy production: aerobic liposis, aerobic glycosis, anaerobic glycosis, and ATP-CP. Depending on your demand for energy, your metabolism will select one or two metabolic pathways.
When your body is looking for ATP, it can derive it from different complex chemical processes (pathways). The first and most basic of these is aerobic liposis. (Liposis>lipid>”fat”). Your metabolism finds free fatty acids circulating in your blood, combines it with oxygen, and can convert it into energy. This process, however, is complicated and time-consuming, and will not suffice when the body has a high energy demand. Hence, aerobic liposis is used during non-exercise (that is, day-to-day life and activities), and very low intensity exercise (your heart rate can be elevated only a little bit).
The next pathway is aerobic glycocsis. (Glycosis>glycogen>glucose>”sugar”). Glycogen is sugar stored in your muscles and a few of your organs, and the average person can store about 1,500-2,000 calories of glycogen. Glycogen is combined with oxygen to derive ATP. You can think of glycogen as your fuel; and your muscles and organs, as your fuel tank. When exercising, your body depletes this fuel. After exercising, you must eat (carbohydrates) to re-fill the tank.
The third pathway, anaerobic glycosis, generates ATP without the use of oxygen. You can imagine red-lining your car, ripping through your fuel reserves, and smelling something hot and dirty from your vehicle’s effort. The amount of glycogen needed for this effort is significantly higher, but because oxygen cannot be utilized, you get a nasty, burning by-product called lactic acid. Lactic acid is what makes exercise burn; the effort from this kind of exercise can significantly wear down muscle tissue (this is not necessarily a bad thing). At home, you’re exhausted, your body is humming, and you are hungry. This “afterburn” from exercise is when weight loss and body re-composition happy. Your body scrambles around, looking for something to convert into glycogen (whatever carbohydrates you eat), and also goes around building and re-arranging proteins, to make your lean tissues bigger and stronger–more prepared, in case it ever has to do that exercise again!
The final pathway, ATP-CP, provides the most explosive energy to your body. ATP stands for adenosine tri-phosphate. CP stands for creatine phosphagen. Basically, when that third leaf on the clover pops (ATP turns into ADP), the body goes immediately to rob that “P” from CP, to rebuild ADP to ATP. Unfortunately, the body has extremely limited amounts of CP. Energy from this system is provided for seconds only.
So, how can you train these systems?
Aerobic glycosis is any sustainable activity lasting anywhere from 20-90 minutes. Even longer, if you are a seasoned endurance athlete. This system is trained by exercise like running, rowing, swimming, or general bodyweight and resistance exercises with high repetitions.
Anaerobic glycosis is a much less sustainable activity, that can last minutes only. This can be anything from strength training (8,10, 12 repetitions) to intervals, to Fartlek training, Tabata intervals, to sprinting, to jumping. Each effort is full tilt,and recovery time between efforts is ample.
The ATP-CP system provides energy for merely seconds. Explosive and full-body recruitment exercises train this system. Examples include some plyometrics, max-out lifting, 10 second sprints/intervals, throwing, etc.
**Note: seldom is the body ever exclusively in one pathway or another. In fact, the body has a tendency to blend them. For example, at rest, the body taps into its aerobic lipolitic (fat burning system), but might rely on the aerobic glycolitic system for up to 30% of its energy needs as well. A multi-step full out effort, such as a Turkish get-up, might switch between ATP-CP and anaerobic glycosis. Endurance lifting will certainly spread over aerobic and anaerobic glycosis.
Each system can be trained and adapted. The more endurance activities you do, for example, the more you will be able to do later. By keeping your body on a bobble between aerobic and anaerobic intensities, you eventually condition your body to accept more work (hence, you become more fit).
How? One way is by increasing the number of mitochondria in your muscles. Mitochondria are basically the “lungs” of your cells, and accept more oxygen. The more oxygen your muscles can accept, the more energy they can deliver towards an effort. This is one reason why it is important not to do the same exercise all the time, as your body becomes more and more efficient. To make gains in fitness, you must always seek new ways to challenge yourself.
To be continued…