Although some people might take issue with an engineering approach that views the body as a working machine, there are a number of good reasons
for doing so.
To begin with, it's easy to relate physiological functions to the workings of other devices that you may be familiar with. For example, if you have a basic understanding of how antifreeze is circulated under pressure in the closed cooling system of a car, you can appreciate how the body adjusts to remain cool during a workout. A second point is that a basic knowledge of cellular metabolic functions will give you a better understanding of the production sites and quantities of useful heat that's created during warm-ups and fatiguing heat that's produced during workouts. This will help you diagnose and reasonably predict the effects of certain actions.
Exercise physiologists are awed by the human body's performance potential. It can perform awesome feats of muscular strength-like lifting two to three times its own weight-and achieve muscular hypertrophy, growing from 12-inch biceps to biceps of more than 24 inches, when it's subjected to specific overload-training regimens. The human machine can also increase its rate of cellular energy combustion 20-fold, increase its uptake of air into carburetor like lungs 30-fold and electrically signal its heart, its fuel/oxygen/exhaust pump, to very rapidly increase to three or four times its idling rate. These processes are controlled and regulated by complex neurological circuits that have data integrations and memory capabilities that rival the most sophisticated computers. Add to them the autonomous internal ability to repair damaged component cells, reduce sludge like cholesterol deposits, neutralize corrosive acids, filter out toxic airborne particles and restore reserve fuel supplies through adequate rest and nutrient uptake, and you have to agree that the human body is one incredible working machine. Remember that bodybuilding is not just muscle building. It also involves maintaining, repairing and improving the human machine.
Muscles contract through a release of energy, and the way in which you deplete your energy stores depends essentially on your fitness level and the type of workout you do. You can help to significantly improve your body size through training and by modifying or increasing your energy stores. In order to design a maximally effective training program, you must know about the depletion and replacement of energy stores.
Food is the body's indirect source of energy, and it goes through a profound series of chemical reactions in the body that are collectively referred to as metabolic pathways. The end product is a compound called adenosine triphosphate, or ATP and it is the body's direct source of energy. If you understand these pathways) you can make safe applications and choices in your training with respect to diet and muscle growth, the onset and delay of muscular fatigue and specificity of training.
It's also important to understand the functions of the respiratory and circulatory systems. Ventilation, which means moving air in and out of the lungs, and the ability to move oxygen into the muscles for the manufacture of ATP and the removal of carbon dioxide are modified by training. Consequently, it's helpful to know how these modifications take place.
Other essential factors include the effects of bodybuilding on the endocrine and skeletal systems. It's more difficult to maintain the body's internal environment during a workout, and adjustments are brought about by the nervous and endocrine systems through the release of chemicals, or hormones, into the bloodstream. The skeletal system is the main support for the human machine, and many positive changes occur to bone as a result of weighlifting.
If you want your car to run at peak performance, you must make sure that all its systems are operating efficiently together. The same goes for the human machine.