In order for your muscles to grow, you have to stimulate them with a high intensity training stress and then allow them to move through the three phases of the recovery process.

There seems to be a number of differing variations of high intensity as it relates to bodybuilding, so lets make sure we are on the same page, okay?

High intensity refers to the percentage of momentary muscular effort being exerted.

If you can curl a 100 pound barbell for 10 repetitions and an 11th repetition is impossible, you have performed high intensity training and have trained with 100% intensity and to the point of momentary muscular failure, if, and this is a big if, you also gave it 100% mentally, not just physically.

And that makes high intensity training a completely different kind of animal.

This is what is meant by the phrase, training to failure, as advocated by high intensity training enthusiasts. In other words, if you are doing a set of barbell curls and you perform as many repetitions as possible until you cant complete another repetition in good form, you have trained to failure.

There is another important point we need to touch on in the above definition and that is the ideal of volitional effort. You see, your muscles are voluntary - they will not contract (work) unless your mind tells them to do so.

You see, intensity, as it relates to bodybuilding, is the possible percentage of momentary muscular and volitional (mental) effort exerted. You can not train with 100% intensity (train to failure) without doing so mentally as well as physically.

The fastest way to make progress would be to stimulate your muscles with high intensity weight training (in order to trigger the adaptive response) and then minimize the stages of the recovery process. The way to minimize the recovery process would be by performing the least amount of exercise needed to trigger the adaptive response - one set per exercise per body part.

One set per exercise per body part is the least amount of exercise we can do and still stimulate muscle mass and strength increases. By performing just one set, you limit the drain on your body's finite energy reserves.

Every set you perform eats in to your limited recovery ability. Your workouts need to be hard, brief, and infrequent if you want to make maximum progress in a minimal amount of time.

Once you've performed a high intensity set on an exercise, you've triggered the adaptive mechanism that will allow over compensation (increase in muscle mass and strength). It only takes this one attempt (one set) to make progress. Performing any more sets will only drain away your body's limited recovery ability.

If you remember, your muscles adapt and grow larger and stronger by being exposed to an anaerobic stimulus that challenges their current existence. In other words, progressive overload through high intensity weight training.

If you train intensely enough, most of you will not duplicate or outperform what you did in the first set. For example, if you train to failure and manage to do 10 reps with 200 pounds in the bench press, you will not be able to duplicate this performance. You may get 6 or 7 reps on the second set.

So what would be the purpose of this set, since it does not come close to challenging your bodys current strength level, and we already know that is necessary in order to cause the adaptive response we are looking for. All youve done is create a much greater inroad into your bodys recovery ability. Although it doesnt seem like much, by adding a second set, youve increased the volume for that body part by 100%!!

However, this is where things get muddy for the skinny hardgainer. For you, it may be necessary to add another set or two. Here's why -

As a skinny hardgainer two things are likely - your muscles have low neuromuscular efficiency and you have more slow twitch fibers.

With lower neuromuscular efficiency your body may need a second set to fire enough muscle fibers to trigger the adaptive response. Thus, a second set could be of benefit.

In addition you need more time under load as discussed in the previous report. In order to satisfy this as well as make up for lower neuromusclar efficiency, you may need to add a set or 2 to each exercise in order to make enough of an inroad to trigger the adaptive response mechanism.

Keep in mind, there are a lot of variables when it comes to designing a proper weight training program. I am not stating that one set per exercise is the most effective way for you to train all the time. But it is extremely effective, if (and that's a big if), you work at a high enough intensity level, something very few people are able or willing to do.