Maximizing Hypertrophy: The Scientific Variables – Part I

maximizing hypertrophy

By Scott Iardella

The desire to increase lean muscle mass is a widely sought after physical attribute for athletes of all levels and general exercise enthusiasts.  However, in regards to understanding muscle building (hypertrophy), it’s been said that we are still in the “infancy” of truly discovering the keys to unlocking maximal response.

New science continues to emerge each year and there’s been a large body of evidence supporting several key variables to maximize hypertrophy.  This article series will cover those variables and what we know so far.

First, let’s define hypertrophy.  It’s simply the increase in size of the muscle tissue cells and it’s components.  There are 2 types of hypertrophy that can be achieved which are myofibrillar hypertrophy, the increase in size of the actual muscle fiber (the myofibril) or sarcoplasmic hypertrophy, the increase of the fluid or gel-like material in the muscle tissue.

This topic alone is a fascinating discussion and while it’s important to understand, you need to know that you cannot train exclusively for one type over the other.

Now that we have a working definition of hypertrophy, let’s look at 3 key variables to induce hypertrophic response: volume, intensity, and exercise selection.



Volume has been called the #1 driving force behind muscular hypertrophy, according to muscle building expert, Dr. Brad Schoenfeld.  Volume is defined as the total reps, sets, and loads performed in a training session.

If you look at volume versus intensity, which we’ll discuss next, either one could arguably be considered the top driver to build muscle.  As a matter of fact, it was the legendary Vince Gironda who probably said it best: “It’s not high reps that work. It’s not heavy weights that work. It’s high reps with heavy weights that work!”

 “It’s not high reps that work. It’s not heavy weights that work.

It’s high reps with heavy weights that work!”

-Vince Gironda

If you remember one thing from this article, remember and apply what Vince said.

What we know is that higher volume, multi-set protocols have consistently proven to be better than single set, lower volume protocols. Again, more volume means more mass, but we also have to remember that we cannot continue to overload the muscles (and our bodies) indefinitely. We need to take it to the edge, but not over the edge.

This is the principle of progressive overload, which states that we need to continue to place a demand on the body to elicit a response. However, this must be used strategically with well designed programming to avoid plateau, burnout, injury, or overtraining.

The bottom line is that volume drives hypertrophy.



Intensity or Volume? Take your pick because they’re both critical for the optimal development of muscle mass. Intensity is defined as a percentage of your 1RM (one rep max).

Let’s make this simple. If you have a 300 pound maximum bench press, that’s your 1 RM. If you’re training session today calls for you to bench press at an intensity of 85% (upper range for hypertrophy) – your training weight intensity is 255 pounds, which you should be able to perform approximately 5 reps (at that intensity).

What the science shows us is that intensities of 65-85% are most optimal for the benefit of hypertrophic response. Less than 65% is not considered sufficient to maximize hypertrophy. Remember Vince’s quote, right?  Heavy weight plus high reps.



The final point in Part I of this article series has to do with exercise selection. First, let’s understand that you cannot “isolate” muscles, it’s impossible. You can target muscles, but you cannot completely isolate muscles in the human body as the body is a complex and dynamic system of integrated joints, muscles, tissues, and nerves.

Now that I’ve said that, what we know is that there are roles for both multi-joint and single joint exercises in developing muscle mass.  For bodybuilding purposes, single joint exercises will be necessary and important to target smaller muscle groups.

What is critically important (and sometimes missed) is the use of the big multi-joint lifts: squats, presses, and deadlifts, for example. The big lifts produce more significant hormonal responses that are necessary for muscle growth and, obviously, develop larger muscle groups – which means we put on more size.

Let’s take the classic example of the legendary Tom Platz to illustrate this point.  Tom’s simple solutions to many smaller body parts (even the upper body) essentially always came back to one thing: squatting.  Specifically, with his high rep back squat routine.

To maximize muscle fullness and density, we can certainly utilize different exercises, different angles, and different mechanisms for stimulation.  But, the big lifts, the fundamentals, have always been extremely effective for hypertrophy. Stick to the basics to get big: squat, press, and deadlift.

We’ve got much more to cover, so look for Part II coming your way soon to dive deeper into the key variables to maximize hypertrophic response.



Schoenfeld, B. The Mechanisms of Muscle Hypertrophy And Their Application To Resistance Exercise, Journal of Strength and Conditioning Research, October 2010, Vol 24, No 10 p. 2857-2872


Related Story:  Using Kettlebells for Size and Strength – By Scott Iardella


As a physical therapist and a strength coach, Scott has spent 3 decades teaching unconventional approaches to strength & performance training for long term health and fitness results. With numerous training and nutrition certifications, Scott is also one of the world’s foremost experts in kettlebell training and the prominent host of the Rdella Training Podcast. — Scott is the author of The Edge of Strength, a comprehensive new book describing his philosophy and methodology of training and performance (now available at