The 3 Key Training Variables to Manipulate for Size

Tom MacCormick

Strength and Conditioning, Personal Training, Sports Science

Training for size isn’t as simple as hitting the gym and blasting a muscle group. You need to provide an appropriate signal to the body to force it to adapt. The signal should be of an appropriate magnitude and delivered at an optimal frequency.


If you fail to provide your body with this signal it won’t grow. Muscle is a luxury item as far as your body is concerned. Luxuries tend to cost a lot. In the case of building muscle, it costs a lot in terms of nutrients and effort. Applying this effort intelligently can drastically expedite the process.



You have multiple variables at your disposal to optimize training for hypertrophy. Organizing and adjusting these variables logically is a key skill to develop if you want to be successful at building muscle. Variables such as, training volume, intensity, frequency, exercise selection, exercise variety, sets, reps, rest, and tempo are all important and require consideration.


The three key variables to understand are:


  • Intensity
  • Volume
  • Frequency


If you can sequentially manipulate these three variables you can progress at the fastest possible rate. This article, I will describe exactly how to do that, but first…


The 3 Key Training Variables to Manipulate for Size


A Quick Review On Program Design Priorities

Before outlining how to organize the three key training variables into a periodized plan it is important to establish a concrete understanding of the aforementioned principles of specificity and progressive overload. Your training must adhere to these principles to be successful. In other words, you must be training in a way that is specific to your goals and in a progressive manner.


Specificity is a very simple concept and the fundamental training principle to base your training program on. Specificity means that training is focused on developing the training adaptation you desire. Many people forget this. They train hard, but they do not train specifically, or more often, they take their eye off the ball and allow chunks of their training to become less and less specific.


I’m sure you know someone who started out wanting to get lean, but then got distracted by improving their total in the squat, bench, and deadlift. Without realizing it their training morphed into that of a powerlifter, rather than someone looking to look good at the beach.


Alternatively, you may have come across someone who was desperate to build muscle, yet got sidetracked in keeping their conditioning on point. Next thing you know they are spending more time chasing 10km personal bests than lifting weights in the gym.



While these above examples of a loss of focus do not violate the principle of progressive overload (they are still training harder and harder) they do violate the principle of specificity. That is why it gets priority status. Training in an overloading fashion is important, but first you must be sure you are overloading the thing that you hope to improve. After all, training for an Ironman will 100% overload me, but it isn’t going to help me build bigger muscles.


Guidelines for Training Hypertrophy

As this article is centered on training for size, here are some specific guidelines to follow to train specifically for hypertrophy. Ensuring your training sticks closely to these will give you the best chance of success.


  • Train using loads >60% 1RM
  • Do most of your training (66-75%) in the 6-12 rep range
  • Most of these should be for sets of 8-10 close to or at failure
  • Do 40-70 reps/muscle group/session
  • For a total of 80-210 reps/muscle group/week
  • Train each muscle group 2-3x/week
  • Use 1-3 exercises per body part (1 for smaller muscle groups)
  • Begin with 2-3 sets per exercise
  • Progress to 3-6 sets per exercise
  • Training to failure is not required, but done occasionally might help
  • Avoid rest periods that are too short and compromise overall training volume
  • Gradually increase training volume over time


You are now armed with hypertrophy specific training guidelines. The next step is to apply the principle of progressive overload.


Progressive Overload

For training to be overloading it must disrupt homeostasis enough to cause the body to adapt. Homeostasis is defined as, “the tendency towards a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes.”


To build muscle you must present an overload to the body that disrupts the equilibrium. Your training must be hard. If you apply the hypertrophy specific guidelines listed above with sufficient effort then you will overload the body. This will cause it to adapt and build bigger, stronger muscles.


So, we know training must be hard to be effective—the bad news is that it has to get harder.


Once an overload has been presented to the body it adapts. Presenting an equivalent stimulus next time is no longer an overload. The body has already adapted to this magnitude of stimulus and it is no longer perceived as an overload. Thus, every subsequent stimulus should be greater than the one which preceded it. This is the progressive part of progressive overload.


In simple terms, your training, on average, must continuously provide an overload to the body. Therefore, you must continually lift more weight, or do more sets and reps at a given weight, to keep providing a sufficiently overloading stimulus to the body to cause long-term adaptations in muscle size.


The Progressive Overload Conundrum

It may be a fundamental principle of training, but progressive overload presents a problem. That problem is that on the face of things our only option to keep progressing is to do ever longer and more arduous training sessions. Time is finite and most of us have work, family, and social commitments that prevent us from spending every waking hour at the gym. Even if we didn’t have these commitments, you cannot indefinitely train harder, for longer, more often without getting injured or overtrained.


So, how can you adhere to the principle of progressive overload without hurting yourself?

That’s where those three key variables I mentioned earlier come in…


  • Intensity: In this instance, is defined by the percentage of 1 rep max used when performing an exercise.
  • Volume: A measure of your total workload per exercise, session, and week.


A simple way to track volume is by using the following equation:


Sets X Reps X Load

Research indicates a dose response relationship between training volume and hypertrophy. While there is both an intensity and volume component to hypertrophy training, research indicates that, assuming you use loads above 60% of your 1RM, volume is the key determinant of success.


While generally people consider the term training frequency to mean how many days a week you train, Brad Schoenfeld has stated that the number of times a given muscle group is trained per week is a potentially more important consideration. For the purposes of this article frequency relates to how often a specific muscle group is trained per week.


Literature appears to indicate that splitting the same training volume into more frequent training sessions is superior for hypertrophy. There is overwhelming evidence to suggest that training a muscle group twice a week is better than once per week. Current research indicates that anything between 2-4 times per week is optimal, but cannot provide a clear answer to whether 2, 3, or 4 times is best.


The interplay between intensity, volume, and frequency is critical to the success of a program. Intensity and volume are inversely related. When one is high the other cannot be (without consequences–injury or overtraining). At any one time, you can only push two of these three variables hard. Over successive phases of training you can manipulate these to constantly provide a novel muscle building stimulus.


Consider this training format example

Phase 1: Upper/Lower split, hitting each muscle twice per week, with higher intensity and moderate volume. (e.g., 3x8 @ 75%1RM)


Phase 2: Increase training frequency and overall training volume by transitioning to training 5x/week using an Upper/Lower/Push/Pull/Legs split. Decrease intensity by moving to slightly higher rep sets with a lighter load. (e.g., 3x10 @ 70%1RM)


Phase 3: Bump frequency and volume up again by switching to training 6 days a week on Push/Pull split (push = quads, chest, anterior delts, and triceps. pull = hamstrings, spinal erectors, back, rear delts, and biceps). Intensity drops and incorporate metabolic stress style techniques (drop sets, etc.). (e.g., 3x12-15 @ 65%1RM)


Phase 4: Strength phase using lower frequency and volume, but higher intensity. For example, training 3 days per week using a whole-body approach. (e.g., 3x4-6 @ 80-85%1RM)


Phase 5: Repeat the process if you want further mass gain or begin cut if you want to drop body fat.


During phase 1-3 the average intensity (% of 1RM) goes down while volume and frequency are pushed higher and higher. This allows you to progressively overload your body via increased training volume. Since volume has a dose response relationship with hypertrophy this is optimal for muscle building and will allow you to reach your muscular potential as quickly and efficiently as possible.


Hey, if you’re enjoying reading this article and nodding along thinking these concepts sound great then, that’s awesome! Would you love to incorporate them into your own training, but you are not 100% sure how to put it all together?


If you answered “yes!”, then, we have just the thing for you. Tom’s Bulk Up Bible 2.0 program gives you a 3-phase training plan based on all the topics covered in his articles for Breaking Muscle.


The plan is designed to maximize your muscle gain. Progressing you past the plateau so many lifters experience after their initial gains. Not only does it give you a training and nutrition plan to follow, but it includes more detailed explanations. The why behind the how. If you want a done for you, 3-month training and diet plan based on both the art and science of training for the size we recommend you pick up a copy here.



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