Training Induced Muscular Hypertrophy – Part 1: Intensity and Volume
Strength and conditioning is often a subject and or field of study taught and executed for the purpose of enhancing athletic performances of trained athletes. Us bodybuilders definitely like to consider ourselves athletes and we are but in the less traditional sense of the scientific term. Bodybuilders borrow many practices from the basic principles of strength and conditioning to produce desired goals. Strength and conditioning is intended to be sport specific and even athlete specific; that is, building skill sets and attributes of the specific sport and specific position in question. Well now you may ask, how can you apply that to bodybuilding if there is not specific position or sport, so to speak. Although no specific attributes in terms or sports skills are required, we do have a goal in mind, hypertrophy or muscle growth. For this reason we borrow many of the strength and conditioning principles.
That being said I would like to begin a series in the basic practices of bodybuilding in terms of training and the alterations of certain training in order to manipulate the body and metabolic systems in order to produce hypertrophy. Training induced hypertrophy or muscle growth is a direct result of alterations to muscular tension, achieving muscular failure and inducing metabolic stress. These three also heavily rely on the manipulation of the bodily hormones as well. The three mechanisms of action of muscular induced hypertrophy can then be broken down more easily into six terms that can be more easily applied to training. These six variables within training that can be manipulated to induce muscular growth are as follows: intensity, volume, rest intervals, volitional fatigue, exercise selection, and repetition speed.
In the first article I would like to address the first two variables; that is, intensity and volume. Before we learn how the manipulation of these two factors within a training program can aid in your training goals of muscular hypertrophy it will be important to define the two terms. Intensity can be described as a particular percentage of one’s 1RM (repetition maximum) and also the number of repetitions that can be performed at said weight. Volume then can then be described as the product of the number of repetitions, sets and load lifted within one training session.
First let’s discuss intensity, which can also be called load. Intensity is arguably one of the most important variables within a training program that can be successfully manipulated for results of muscular growth. Intensity, as said before, not only refers to percent of 1RM but also repetitions, which can be classified as low, moderate, or high repetitions. High repetitions have proven to no do much in terms of muscular growth. This can be attributed to a few different reasons. One of the possible reasons being that the amount of weight lifted in terms of percent 1RM when performing high repetitions, is simply not heavy enough to stimulate the fibers or break down the muscle fibers to a degree that would produce hypertrophy. Low repetitions, on the other extreme, have also been proven to be not as effective in producing hypertrophic results either. However, low repetitions do spawn great strength gains, this does not always mean large amounts of hypertrophy. Moderate repetition ranges, that is from 6 -10 repetitions, has proven most effective for muscular hypertrophy. It is important to note that the 6 -10 repetitions that are carried out during this type of set are difficult. Moderate repetition range does not mean a light weight for a simple 6 -10 reps. It is more so that the load dictates the repetitions. That is, an intensity between 60% – 85% of 1RM should elicit a repetition range of 6 -10 repetitions. Various studies have concluded that it is at this intensity that the modification of genes related to muscle growth are activated. Moderate repetition ranges are beneficial to bodybuilders and their training styles for many reasons. Moderate rep ranges depend on anaerobic glycolysis, which causes a buildup of metabolites. This buildup of metabolites has a significant impact on anabolic processes in several ways. In general, the moderate repetitions range has shown to increase anabolic hormone responses. More specifically, GH and testosterone are elevated. Another benefit to moderate repetition training range is that this maximizes the hydration of the muscle at the cellular level. This happens because of the nature of the blood flow into and out of the muscle during a moderate rep range set. The veins that are carrying blood out of the muscle are compress while the arteries are simultaneously still bringing blood into the muscle. This is what creates what we all know as the infamous “pump”. One last benefit of moderate rep range is the increased amount of time the muscle spends under tensions as opposed to a lower repetition set. With more time under tension this allows for more micro damage at the cellular level, which is, as we know, absolutely necessary for muscular growth. This is based on the break down build up theory that most of us operate off of.
Now, lets discuss volume. Volume as we said before is the total work done in a training session and is the product of the reps and sets within a training session. Volume in itself is sometimes hard to separate from other factors within the training program. Because certain loads are lifted volume will also vary. For example if you were performing a total body workout, it is theoretically impossible for you to train at adequate intensity for every exercise that you perform. This is why most bodybuilders if not al bodybuilders engage in a split routine. This allows for heavier daily loads to be lifted per body part each day. Volume is a fine balance. Too high of volume can lead to injury but not enough volume can lead to minimal gains. Volume should also be cycled in order to produce desired gains. That is for periods of time the volume should be increased to produce and overreaching effect but then should be brought back down and then back up and so on and so forth. Most bodybuilders do this without even realizing it. For example, in the off-season many people lift heavier with a smaller rep range as opposed to when training for a show. It is important to note that the intensity may fluctuate within the 60% - 85% range but stays within this range to ensure there is no loss in muscle mass. As one is preparing for a show, rep ranges usually increase while the weight lifted may be reduced, thus altering the volume. This is why trying to compete year round is potentially dangerous and why most all people take time off. You cannot train at a high volume and high intensity level for extended periods of time because this will results in injury. Lengthy exercise sessions are also not necessary or smart for that matter. Increased time results in less effort as well as the increase in cortisol levels. Both of which are no good for hypertrophy results.
That 
being said, however, it is important to discuss the appropriate amount of sets needed to induce muscular damage and in turn muscular hypertrophy. Various studies have shown, and I’m sure that we all know by now, one set is not enough to induce muscular growth. The trends show that a minimum of 2 -3 sets is needed to produce a hypertrophic response and 4 -6 sets may actually be beneficial. Keep in mind this is per exercise, not per training session. Some may argue that the Arthur Jones style system does work and only calls for one set of each exercise with a rep range of 8 – 10. However, this type of training style is designed to go to muscular failure. The only problem with that is that even if we think we are at muscular failure we usually are not. Volitional fatigue is only achieved basically when you lift until you drop the weigh. Unless you are in a controlled environment or training with a partner, this style of training is close to impossible and poses some safety risks. This is why the 4 – 6 sets of moderate rep range with a 60 – 85% 1RM intensity is designed to best suit the average bodybuilder.
So, after discussing intensity and volume, it will be important for you to look at your training and exercise regime and plan it out not only day to day, but also observe the changes you are making from workout to workout and month to month and so on and so forth.
Sources and Photo Credits:
Goto, K., Nagasawa, M., Yanagisawa, O., Kizuka, T., Ishii, N., & Takamatsu, K. (2004).
Muscular adaptations to combinations of high and low-intensity resistance exercises. Journal of Strength and Conditioning Research, 18(4), 730-737.
Krieger, J. W. (2010). Single vs. multiple sets of resistance exercise for muscle
hypertrophy: a meta anaylsis. Journal of Strength and Conditioning Research, 24(4), 1150-1159.
Schoenfeld, B.J. (2010). The mechanisms of muscle hypertrophy and their
application to resistance training. Journal of Strength and Conditioning Research, 24(10), 2857-2872.
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