Muscle Building Techniques

When you work out at the gym you put a lot of effort to increase your muscle mass, decrease your bodyfat percentage or, simply, to be fit, But you know how your body really works? There are 2 kinds of exercise: aerobic/cardiovascular exercise and resistence exercise. Each of these two types entails the use of different bioenergetic pathways to produce the energy required to perform the exercise.

To simplify, the aerobic/cardio type, as the name implies, primarily taxes the cardiovascular system and uses an aerobic (with oxigen) pathway. Most of your daily energy needs, including your needs right now while reading this article, are fulfilled through this pathway.The aerobic pathway is the lowest and can not be used to fuel explosive, high intensity exercise.However, the aerobic bioenergetic pathway can produce energy indefinitely because it taps into the richest energy source available to the human body: fat. In addition, aerobic energy production does not result in waste byproducts, such as latic acid, which at high concentrations cause temporary muscle failure.

The other family of exercise, resistance exercise, places most of the stress on the skeletal muscles.
This type involves the anaerobic (without oxigen) bioenergetic pathways: ATP/CP and glycolysis. At first, it may seem peculiar that muscular work can proceed in the absence of oxigen. But, the basic
energy unit for all human activity is ATP. The human body has a limited supply of ATP (located along with glycogen and creatine phosphate in the muscles) on hand to use for inmediate energy needs.
You only have enough inmediately available stored ATP for one momentory, maximal burst of muscular output. After that, a compound called creatine phosphate (CP) swings into action donating phosphate molecules to convert spent adenosine diphosphate (ADP) back into adenosine triphosphate (ATP), thus regenerating your ATP supply. From the moment readily available ATP is depleted, available energy per second declines and so does maximal muscle contraction force, as other fuel sources must be converted to ATP. After the first few seconds, during which stored ATP is exhausted and CP is tapped, muscular power output drops-off slightly. In practical terms, if you are straining at maximum effort to lift a weight, and it has not gone up within four seconds, it´s not going up. During the short window of time when "high energy phosphates" (ATP/CP) are used exclusively, neither protein, nor fat, nor carbohydrate, nor even oxygen is required. Within seconds, the window of completely anaerobic activity closes, at which point, if maximal effort persists, a different bioenergetic pathway is engaged.

After about 10 seconds of maximal muscular effort, both ATP and CP become depleted, and glycogen becomes the predominant fuel source; this is the glycolitic bioenergetic pathway. At this point, with glycogen being used to phosphorylate ADP into ATP, muscular power output drops-off further because of the slower rate of energy transfer via glycolysis. When glycolysis is the primary pathway utilized, maximal effort will only produce 45% - 70% maximum output. This is why in Track & Field, the 100 meter sprint lasts between 10-12 seconds (after that it´s no longer sprint)

Technically, since maximum muscle contraction cannot be maintained beyond 5-6 seconds, even the 100 meter sprint is not a maximal output competition (in contrast to powerlifting, the javelin, the shot-put, or the 40 yard dash). With victory in the 100 meter sprintm ussually coming down to a fraction of a second, them winner is often the person who slow down the least from the midway point to the finish line. One byproduct of glycolysis is latic acid, which is the responsible for the familiar burn that accompanies high intensity exercise and which contributes to the momentary muscle failure that occurs with this type of exercise. The accumulation of latic acid indicates that you are incurring an oxigen debt. Anaerobic glycolysis allows for energy formation even though oxigen supply is inadequate relative to the demands of the activity. Like all debts, the oxygen debt must be repaid. Oxigen is necessary to replenish high energy phosphates depleted by exercise, and to clear-away latic acid. This explains why, after a short burst of intensity, you breath heavily; you are paying back the oxigen debt that was incurred during the anaerobic period.

If you train with weights, you know that you can lift more wheight if you wait longer between sets. This is because lactic acid, which impairs muscle function, is increasingly removed over time and high-energy phosphates are regenerated during these brief mini recovery periods. Lower intensity exercise, on the other hand, uses the "pay as you go" aerobic pathway, in which there is no oxigen debt. Thus, with low intensity aerobic exercise lactic acid does not accumulate, distinct and abrupt muscular failure does not occur, and respiratory rate remains stable.
Trained athletes incur less oxigen debt at a given intensity level due to a higher blood lactate threshold
resulting from enhanced lactate clearance. In fact, the difference in lactate treshold between trained and untrained can be quite dramatic; and along with improvements in neuromuscular efficiency, thsi accounts for much of what commonly termed "strentgh" and "endurance". Increase lactate treshold is one of the many stress specific adaptations that occur in response to exercise. Weight training is a classic example of an activity that draws heavily on the ATP/CP and glycolitic pathways and which thereby, causes improved efficiency of the systems.

Resuming, fat can only be burned in the presence of oxigen (through the aerobic bioenergetic pathway, which is used for 95% of daily energy needs) Glucose and glycogen can also be used in the presence of oxigen (although, as I explained above, for short periods sugar can be burned without oxigen to satisfy high intensity exercise) What percentage of sugar or fat you use for 95% of your activity depends on which metabolic pathway is dominant, the sugar-burning or the fat-burning pathway. This balance depends on your diet, exercise and hormone balance