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Pritchard: Rep range can help with optimal muscle gain

By Jimmy Pritchard Better Version of You
Jimmy Pritchard

Most people are somewhat familiar with the association between exercise reps ranges and their targeted effect on the body while resistance training. The heaviest load one can lift at a given weight correlates with maximal strength, while anything one can do in excess of 20 times or more clearly signifies muscular endurance.  Somewhere between these two ends of the spectrum, however, lies muscular hypertrophy. Some coaches and trainers say 10 reps is the magic number, while others believe a range of 8-12 is more accurate. So, what is it? Will I grow huge biceps if I do 4 sets of 8 or 3 sets of 12? Quite honestly, it doesn’t really matter, there is no magic window.

How does one gain muscle?

While you might already be scratching your head wondering why rep ranges aren’t as big of a deal for gaining muscle as you’d previously thought, it’s important to understand how muscular hypertrophy occurs in the first place. There are basically three main ways that one can enhance muscle protein synthesis via the mTOR pathway resulting in increased muscle cross sectional area. The first way is through increased muscular tension, which occurs through using a heavy load while performing exercise through a full range of motion. As a muscle spend more time under a given weight, and the load increases, this increases what is known as the time under tension (TUT). Through the use of slower tempos, pauses, and increased weight one can dramatically increase their TUT in a given exercise. The second method to increasing muscular hypertrophy is through muscular damage, most often associated with severe soreness or the delayed onset muscle soreness (DOMS) one feels multiple days after a hard training session. This occurs because of small micro tears within the muscle fibers themselves, especially during eccentric and concentric muscle contractions. When given adequate time to recover and proper nutrition, the muscle fibers repair themselves and allow one to handle a slightly greater stimulus the next time around. The third method with which muscular hypertrophy occurs is through metabolic stress. This often occurs through the use of lighter weights at a higher given rep range and is associated with the burning sensation one feels while lifting. As the muscles continuously contract and relax blood pools and muscle cell swelling occurs. This restricts blood flow and ultimately induces muscle hypoxia which in turn allows for the build of metabolites such as lactate and hydrogen ions. These metabolites induce an anabolic effect which leads to molecular cell signaling for increased hormonal responses on the body. Each of these three methods play off of one another and should be used in a complimentary fashion to yield the best training results possible.

What really matters

Understanding what drives muscular hypertrophy from a physiological standpoint easily explains why subscribing to an arbitrary rep range is suboptimal for training. Through the manipulation of the three previously mentioned variables, one can control the volume load they are training with, which is perhaps one of the most important considerations of all when seeking muscular hypertrophy. 

Volume load is a simple formula that’s calculated as: Sets x Reps x Load = Volume Load. Increasing volume load through a properly periodized program will ensure that greater stimulus is being place on the body and ultimately driving adaption. Take for example the previously mentioned reps/sets count of 4×8 or 3×12. If I lifted 4sets x 8reps x 100lbs that would be 3200lbs versus 3sets x 12reps x 100lbs which would be 3600lbs. My 3×12 would likely yield greater results with all things being equal (tempo, TUT, etc.) because it’s a larger stimulus. Now imagine that I did 4sets x 8reps x 150lbs = 4800lbs, versus 3sets x 12reps x120lbs = 4,320lbs. Theoretically, my 4×8 would be better for muscular hypertrophy. You can see that the rep range is only one factor in the equation, meaning that increased volume load can be achieved in a variety of ways with no magic rep range truly existing. 

What is interesting, however, is that somewhere in the 8-12 rep range still appears optimal for inducing muscular hypertrophy because it strikes a balance between moderate weight at a fairly high rep range. Attempting to do 50 reps with 10lbs will only result in a 500lb volume load, whereas 5 reps at 100lbs could achieve the same result in less time. Conversely, it would take 10 sets of 1 repetition at 300lbs to reach 3000lbs, whereas 3 sets of 10 repetitions at 100bs would equal the same volume load despite a much longer rest period between sets being required for the 300lb single repetition sets. Remember however, that this relates to muscular hypertrophy, volume load while important for muscular strength, does not play nearly the same role as it does for gaining muscle. Additionally, one can only handle so much volume before they inadequately recover. That is another article for another day. 

All in all, my hope is that you have a greater understanding through which muscular hypertrophy occurs and the way in which you can manipulate your training. It’s important that you do not get stuck in a dogmatic routine following an arbitrary rep count simply because that’s what you’ve always thought was best. Doing a little research and digging for deeper answers is important if you truly want to get a grasp on how training works. Thank you for reading as always!

Jimmy Pritchard has a MSc in Exercise Science from Edith Cowan University and is a Certified Strength and Conditioning Specialist through the National Strength and Conditioning Association. He is the Director of Strength & Conditioning at Ski and Snowboard Club Vail. Contact him at 970-331-3513 or jpritchard@skiclubvail.org.  Check out his website http://www.pritchardperformance.com.


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