Muscle hypertrophy, defined as increasing the size of a muscle, is of paramount interest not only for aesthetic reasons, but vastly more important, for health and performance reasons. Muscle is now viewed as an endocrine organ and it turns out, fighting to maintain and increase the amount of muscle we have is one of the most important health behaviors we can engage in.
Our colleagues in the department of Kinesiology at McMaster University in Ontario, Dr. Stuart Phillips (who will keynote at the 2020 Resistance Exercise Conference, hosted by Discover Strength in March) and Robert Morton (Ph.D. candidate who keynoted our conference in 2018) recently published a new review paper summarizing the different variables of muscle hypertrophy. This paper has led to much discussion among our staff and strength training practitioners world-wide.
I encourage you to reflect on these guidelines and apply them to your own training…
How much weight? It doesn’t matter. You can use a light weight, a moderate weight, or a heavy weight; as long as you reach muscle failure, the degree to which your muscle hypertrophies will be the same.
Frequency? The majority of resistance training induced muscle hypertrophy is stimulated by one session per week while a second or third training session may increase hypertrophy with diminished returns. Stated otherwise, one workout in a week produces MOST of the benefit but it does appear that a second and third workout has a positive impact on hypertrophy.
Rest? There appears to be no difference in muscle hypertrophy from taking short rests (30 seconds) between sets or long rests (2 minute) between sets.
Focus? Adopting an “internal focus,” that is, thinking about the muscle that you are actually contracting, results in superior increases in muscle hypertrophy (when compared to focusing on simply moving the weight from point A to point B, known as an “external focus”).
Other variables? It appears that variables such as time of day, single versus multiple joint exercises (pec fly versus a chest press), and exact recovery days between workouts all have a negligible impact on muscle hypertrophy. The one additional variable that does seem to impact muscle hypertrophy is the inclusion of eccentric muscle contractions (lowering the weight); focusing on lowering the weight under control (or with a heavier weight) appears to be superior than lifting the weight (concentric) and simply letting the weight drop.
Differences between men and women? Although men have greater absolute amounts of muscles mass and changes in muscle mass when compared to women, relative changes between men and women are nearly identical and interestingly, women respond similarly to all of the above variables discussed. This is noteworthy as men have ten times the amount of circulating testosterone when compared to women.
The most important variable? Momentary muscle failure. The authors conclude, “Maximizing resistance exercise training hypertrophy is chiefly determined by intensity of effort and not categorical manipulation of specific resistance training variables.”