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Friday, January 25, 2013


This week the discussion is a bit more technical but important, for some of you may not realize that it might be harder for you than others to get your body to the results that you desire. Do you know why? Does it just depend on genetics? Can you change the way your body works to get and keep building it the way you want?
We gave an introduction as to how the human body produces energy, but now we will get more into it because the types of energy system can be manipulated, even for non-athletes so that you can maximize your results whatever they are. So for exercise we need to produce greater amounts of energy for muscle contraction under extra tension. But the difference in the type of muscle is defined by the speed in which they produce energy (ATP). Producing energy means that your muscle cells have more or less numbers of mitochondrias (oxidative enzymes for cell respiration), and more myoglobin to release oxygen in the blood stream. Due to this the microstructure of the muscle, called the fiber (for those beginners) can be considered of slow twitch or fast twitch. The slow twitch or Type I Fiber contains many mitochondrias and myoglobin, characterized by the color of blood due to its affinity to oxygen which is used in aerobic metabolism and have high resistance to fatigue. Fast twitch or Type II Fibers are characterized by their cells releasing calcium in faster speed activating enzymes to produce energy quickly. Fast Twitch Fibers are subdivided in to Type IIa, which is a mix of fast and slow twitch, and Type x which due to faster enzyme activity it takes a lot of energy for its use. For resistance training we use mostly the Fast twitch fibers, and those that have more quantity of these fibers usually have an easier time to build muscles. This is defined by genetics, but you are also able to manipulate the energy systems so that you can activate your slow twitch fibers (for endurance results) or fast twitch fibers (for muscle growth, strength or power). You are born with one Muscle Fiber Type predominating over the other so that is why some have a hard time to put on muscle mass, and there is no need for great effort for others
Bioenergy is the flow of energy in the human body, and metabolic pathways capable of converting nutrients (mostly carbs) into energy biologically useful. There are three metabolic pathways for production of energy for exercise. The first one starts in the digestive system with the breakdown of carbs, producing energy for the first 10 seconds of exercise at a very high intensity. This is the Phosphagen or ATP-CP system, where through the creatine kinase enzyme (the supplement creatine helps with this) helps to produce ATP. This energy system is usually used in programs for hypertrophy. It is energy that lasts for a short time but produced quickly with the availability of carbs. To recover your full ATP-CP energy reserves it takes only a few minutes,
The second energy pathway uses the nutrient (Glycogen) stored in the cells of muscles or liver. It is called Glycolysis, and provides energy for up to 2 minutes of unstopped physical activity. Without the presence of oxygen the product from Glycolysis (pyruvate) is transformed into lactate which causes the burning sensation. With the presence of Oxygen, lactate can be used in its own cycle (Cori Cycle) to produce energy anaerobically. High intensity exercise uses this energy system and it takes 2 to 3 hours to fully recover energy stores.

The third and last energy production system is the Aerobic System. When there is presence of oxygen, the pyruvate that came from Glycolisis enters the Krebs Cycle (Tricarboxylic Cycle or Citric Acid Cycle). In this case pyruvate is transformed into Aceytl CoA (Coenzyme A) to be used with Oxygen. This energy system is used from 2 minutes onwards of exercise at an intensity of low to moderate. In really low levels of intensity Acetyl CoA can also be used in the Beta Oxidation cycle where triglycerides are broken down and transported to the mitochondria to be transformed into energy. This is called Fat Oxidation, but this is not optimal because other energy systems take over before this system kicks in. Full recovery from the Aerobic system takes about 24 – 48 hours.

Logically you can come to the conclusion that most people doing resistance training use the ATP-CP energy system, and since we have already discussed that Type IIa muscles are faster, they must use the Phosphagen System or Glycolytic System to produce energy for muscle contraction, and the rest intervals (up to 2 min) are for recovery. Most in the gym have the desire to maintain or increase muscle mass and reduce fat, so planning the training program according to your body is important. So if you don’t know what muscle fiber type is predominant in of your body parts, you should first plan to find that out by using the anaerobic energy systems to see which works best for you to increase your muscle mass. Those who have a Slow Twitch Fibers don’t have to work as hard on the Aerobic System to lose fat. Everyone should train all of the systems changing up the intensity, volume and rest interval, for even if you don’t want to, depending on how you train you might be using all of the energy systems anyway demonstrating that resistance training alone can bring all types of results.

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