First, as a recap, there are two basic types of muscle fibers- type I (slow twitch) and type II (fast twitch). Type II can be broken down further into IIa and IIb, which are intermediate and true fast twitch fibers, respectively, but for the sake of brevity, I'm going to address them together as type II. Type I fibers are slow to contract, have more mitochondria, and are surrounded like the Texans at the Alamo by capillaries, except the capillaries pretty much serve the purpose of bringing in live strippers and dragging out the dead ones from Ben Affleck's trailer, rather than killing those valiant Type I fibers, Mexican style. I know, that was a bizarre analogy. In any event, the capillaries illustrate exactly the purpose of those fibers, as they carry in nutrients and rid those fibers of the waste generated by aerobic activity. As you'd guess, they're fairly weak, and far less dense than Type II fibers. By contrast, Type II fibers contract and relax far more quickly, have higher glycolytic activity, and store a shitload of phosphates and glycogen. They suffer from a paucity of the capillaries you'd find in the type I fibers, but they replace them with glycogen stores, which allow you to look huge and ripped during a supercompensation phase, and store quick-draw energy directly in the muscles for explosive, heavy lifting.
Not designed for jogging.Everyone has a blend of both types, which varies based on a combination of genetic and ontogenic factors. Basically, you've got the frame of the house built but your genetics, and then the details filled in by lifestyle and training history. On the genetic side, you're obviously going to display the characteristics associated genetically with your ethnicity, so that people of West African descent, for instance, will display a more muscular physique, "with a smaller natural lung capacity and .... 70 or 75 percent of [type IIb muscle fibers] when they are born." (Chicago Tribune) Ontogenic factors then play a role, so that one's level and type of activity throughout one's youth can play a major role in the development and distribution of muscle fibers. Thus, you could have two guys who are virtually the same size and shape, following the same programs for a three months at the outset of lifting, but with remarkably varied strength levels at varied lifts at the end of the three months. They'd find, however, that the longer they trained together, and the more they followed similar or identical training plans and diets, they'd make headway at closing the gap between them. They would never, ever, have identical builds or lifts, but they'd close the gap a bit. This would occur because all muscle fibers can respond to athletic training by improving their ability to perform, according to the manner in which they're trained. Doing a shitload of cardio like you're a low-rent Lance Armstrong would cause your musculature to transform itself accordingly, increasing the mitochondria and capillaries in Type II fibers until they came to resemble Type I fibers. Conversely, murdering the weights will enhance one's phosphagen system, making one's type I fibers begin to resemble Type II fibers in form and function. They'll never make a full transition, but your body will do it's damnedest to keep you in the game. (Nutrient Timing, p.151)
No amount of training is getting this chick into the Olympics for weightlifting, unless it's because she's impaled on someone's cock.
Adding to this disparity in muscle fiber percentages, and the efficiency of non-ideal muscle fibers for the type of exercise in which one is participating, are a variety of biochemical factors. No two people are exactly alike in the manner in which their body processes any nutrient or hormone, to the point where medical doctors admit that "what we can't do yet, is to identify the most appropriate modality of management for individual patients, based on the specific abnormalities each person has." (Metabolic Man, p.157) If doctors can't even get dosing regimens exactly correct for dying patients, due to interactivity issue with both the patient's diet and existing pharmacological regime, in addition to their individual biochemistry, you'd be hard pressed to show me a single fucking "expert" who can tell me exactly what an exercise will do for me when I utilize it, especially when it's broken down further into frequency, loading, and rep scheme. Additionally, they're not going to be able to accurately predict what my recovery time is, because there are far too many factors that contribute to that beyond those I've already mentioned, like one's nutrition and sleep. Insofar as nutrition is concerned, that's not even an accurate indicator, due to the fact that gastric juices have extreme variations in enzyme content from person to person, which would drastically affect their rate and level of individual nutrient absorption. (Biochemical Individuality, p. 83) Additionally, people utilize amino acids very differently, ranging from 2% utilization to ~99%, and the enzymes necessary to bring about the oxidation of certain amino acids are almost wholly absent in some people (Biochemical Individuality, p. 81) Bizarre, right? That's how it's possible for you and a buddy to eat exactly the same things for two weeks and have completely different patterns for shitting and pissing, in addition to wholly different volumes of excreta, the entire fucking time. (p. 112)
Thrown in on top of the fucking mess you've got before you is the fact that your organs aren't the same size or shape as anyone else's, or even in the same place. Heart size, shape, and function vary widely in individuals due to genetics, diet, and exercise, which obviously has a massive effect on the metabolism in every part of the body, as every function in your body is limited by the quantity and quality of blood it receives ( p.32) Thyroids also vary in weight from 8-50 grams, and the shape of them varies to the point where in many people the glad is actually two glands connected by a narrow isthmus. (BI p. 93) As you can imagine, the function in one's thyroid would necessarily be just as varied as it's shape and location. Your pituitary gland, which controls GH production, also varies widely, and there's a 58 fold excretion range in steroid excretions for males- so even if everything else is the same, your excretion and uptake of testosterone and GH can differ so widely that there's no way a program will affect two individuals exactly.
By now, if you remain unconvinced that 6 x 3 x 3RM three times a week on any lift would affect me wildly differently than it would you, you should shut off your computer and go drown yourself in your fucking bathtub, because you're unequivocally severely retarded. There is no humanly possible way to predict what effect a given volume of any exercise will have on an individual, unless it's so extreme that it will definitely have a negative impact due to its severity or laxness. Thus, when someone says you lack balance in your program, save your breath and simply curb stomp them, because they're fucking parrots who are wasting decent oxygen and your time.