If you are reading this straight through you will have already read about how to pick your exercises and how many to perform during one training session. Once you have a list of exercises to perform during any particular session you must answer a few more questions:
The criterion for determining the best answers to these questions include:
Bodybuilders typically do anywhere from one to twelve sets per muscle, and some go up to twenty or fifty sets. It is clear that there is either some number of sets which is best or some criterion by which the ideal number may be determined for each individual. Most bodybuilders both claim that there is no one best way to train and that there is no systematic account of which best way any one individual should train. This is a type of mysticism.
In order to increase muscle size we must increase muscle strength. The size of a muscle is directly proportional to its cross sectional area. Strength means the momentary maximum force which the muscle can generate. Individuals can rarely actually make their muscles apply the maximum force of which they are capable - except for hysterical mothers with children trapped under cars. This is because the neurological system is incapable of generating an absolute contraction in the muscle. But the maximum force the muscle can generate at any one time is closely correlated with how much force it can sustain for short periods of time. In other words, a muscle that can generate fifty pounds of force at once can generate something close to that for, say, forty to seventy seconds.
Since our goal is to increase muscle size we must increase muscle strength. Endurance adaptions result in at best small size increases, due to a higher volume of blood in the muscle. Significant size gains only come with improvements in strength. Since the body does not want to grow, in the sense that it will only increase the size of the muscles in response to an applied stress, you must apply the sort of stress to the body where adapting to the stress requires an increase in strength. Read that last sentence over again if you didn't get it the first time.
Resistance training, where the resistance can be increased over time, is the best way to tax the strength of a target muscle. To adapt to ever increasing poundages on, say, tricep extensions requires an increase in the strength of the tricep muscle. While initial adaption to a pushup regimen will require an increase in strength, very quickly the length of the pushup "set" will be long enough the it will tax the muscle's endurance, resulting in adaptions which will not increase its size. A point will be reached where failure will occur not because of a lack of strength but because of a lack of energy producing organelles in the muscle cells.
To stimulate growth one must tax the strength of the muscle - one must force the muscle to exert near-limit force for less than a minute at a time. To do that one must perfom one set of exercise.
If that one set is performed to a point of muscular exhaustion, and takes less than a minute, the muscle can only adapt by becoming stronger. Increased endurance will not help the muscle survive such short stresses - only great strength will do that. That one set must be very intense, or no adaption will be stimulated. By intense I mean that the muscle must be generating very high amounts of force (relative to the maximum force generating capacity of that muscle).
Suppose you are thinking about doing a second set. If that set is less intense than the first, it will not stimulate further strengh increases. At best it will stimulate an increase in endurance - because to survive two sets with several minutes rest in between them the muscle need not be stronger, only better able to clean out waste products and regenerate ATP levels. At worst it will slow growth by inflicting further damage to the muscle, damage which must be repaired before growth can occur.
If the second set is more intense than the first, requiring greater strength to perform, then the first was as useless and counterproductive as the second set in the previous example. If the second set is just as intense as the first, then again it is useless.
Therefore the best number of sets to perform is one, as long as that set is of high intensity. A beginner may require more, because he may be unable to generate a high degree of intensity. A person with low motivation may also require more sets for similar reasons. One set is certainly safest, as the amount of work done by a fatigued muscle is the lowest.
Remember, in order to stimulate in increase in muscle size you must stress the muscle in such a way that adapting to that stress requires an increase in strength.
The most obvious way to stress the muslce in that way is to force it to generate more force than it can. That would force the muscle to grow stronger to adapt to the stress. That is, of course, impossible. Luckily, the human body doesn't require that. All you have to do is tax the strength of a muscle - force it to do something that requires nearly all the strength that it has. One way to do that is to perform one maximum effort rep in an exercise.
The problem with the one rep set is that it does not "use up" the strength of the muscle very well. Suppose you can incline curl fifty pounds strictly only once. You fail when the biceps can no longer generate enough force to lift the dumbell. If, however, you curl forty pounds to failure, over several reps, you have taxed the strength of the muscle such that it is momentarily much weaker - you have made greater strength demands of the muscle. The strength has been diminished further, and it must in turn adapt to the stress with greater gains in strength - which yield greater gains in size.
Strength is not correlated closely with the ability to sustain force for periods of time much longer than a minute. If it were, marathon runners would have large legs. The world record holders for pushups performed during a day and for situps performed during a day were not very large, or very strong. They did have muscles which had a lot of endurance - they were well adapted to utilizing energy, and to clearing out metabolic waste products.
Your set should not last longer than about a minute. It is force generated over a minute which is correlated with strength, and much longer sets will not result in strength adaptions. Forty seconds should be plenty to make hefty inroads into the strength of a muscle and result in size increases.
Unless you lift very explosively (which is quite dangerous) you won't be able to perform seventeen thousand repetitions in less than sixty seconds. You should be able to perform eight to twelve, however, with a standard cadence, or fewer if you do them very slowly. I will discuss rep speed later in this document.
You should use enough weight that your eight to twelve reps are extremely taxing for the muscle. If you can see properly, are not nauseous, and have sensation in your extremities, then you have not taxed the muscle extremely. More to the point, you should feel excruciating pain in the target muscle. This is called "training to failure." You must also be continually increasing the poundages used. If you do not, then you will not stimulate continuous size gains. The muscle will adapt to the stress, and will then remain constant in size. You must continually add weight to your exercises.
Given that you want your set to extend for forty to seventy seconds, you can break that time up into anywhere from one super slow rep to thirty fast, ballistic reps.
When a repetition is performed in less than two seconds or so it is a ballistic movement - momentum, not force generated by the muscle, gets the weight through much of its range of motion, taking stress off the muscle. This is bad for two reasons: First, it reduces stress on the muscle, making the exercise less productive. Second, it greatly increases the chance of injury. When a heavy weight is moving at high speeds hear your body, worry.
You should take at least two seconds for the concentric, or raising, of the weight, and two for the eccentric, or lowering, in order to maintain maximum stress on the muscle. Many recommend extending the eccentric portion to four seconds because some research has shown that the negative portion of the rep is the most productive. I do this myself. Some advocate even longer rep times - up to thirty seconds. As long as your total set length does not exceed seventy seconds, and you are comfortable with your reps, anywhere inthat range should be fine. Be aware that on poorly designed or maintained machines friction could become a serious problem with slow rep speeds - it could greatly reduce the productivity of the exercise.
Always maintain perfect form. Every exercise is picked because it stresses one specific muscle or muscle group. Cheating removes the stress from that muscle, making the exercise less productive. Cheating at the end of a set may help increase intensity, but only as a last resort.
Keep your reps slow and deliberate and use good form, and you should be able to annihilate a muscle with one set - in one minute. You'll never need seventeen sets a bodypart again.