29 Apr Maximal Reps and Volume For Muscle Growth
The number of reps that should be performed per set on a given exercise for muscle growth is often misunderstood. Rather than always solely referring to reps, you should know and use a percentage of your maximum on every lift to determine the correct load for the exercise. In addition, training according to your muscle fiber dominance can play a huge role. Not knowing any of these factors will impede progress in the gym.
Muscle Fiber Fatigue for Growth
In 2012, a Cameron J. Mitchell et. al study reviewed what the effective load of a 1RM (rep max) would be to stimulate muscle growth. One group performed 30% of their 1RM for 3 sets to failure, another performed 30% of their 1RM for 1 set to failure, and the last group performed 80% of their 1RM for 3 sets to failure. The study was conducted for 10 weeks.
They found that training either 30% or 80% of your 1RM for 3 sets to failure stimulates the same rate of muscle growth. The weight, number of reps per set, and volume didn’t matter. The most important thing was “true” muscle failure, not simply quitting before the set gets tough and wasting the last few reps. You’ll need to perform the lift until your muscles can’t continue going with good form. Another way to put it is this, “It’s simply the incapacity to maintain the required amount of force output.”
However, if you’re serious about lifting, you’re probably not interested in using small weights for 25 or 30 reps to produce muscle failure.
Rep Range and Muscle Fiber Dominance
I’ve often told clients that if a trainer made me do more than 10 reps on most exercises, I’d probably slap them in the face or refuse to train. It’s not a question of whether I can do it. I’ve always found that performing a high number of reps simply bores the fuck out of me. I’d rather watch paint dry in the dead of winter. It’s also the reason why when I attempted to run cross country in high school, I was fucking awful. Muscular endurance training isn’t my cup of tea.
The style of training, rep range you prefer to stick with, and the amount of volume trained per muscle group over the course of a week is in large part due to your ability to maximize the recruitment of high threshold motor units (HTMUs). HTMUs have the greatest potential for muscle growth, highest force, and power output. They’re what most people would refer to as “type II” muscle fibers or “motor units”, fast motor units, and glycolytic muscle fibers. The genes that highly effect muscle fiber composition can be broken down into six classifications (ACTN3 gene types), but for the sake of simplicity, we’ll discuss them in terms of the classic Type I (slow) and Type II (fast).
Type II (Fast Twitch)
Individuals who have more and/or a better ability to recruit Type II muscle fibers have highly efficient nervous systems. The nervous system is responsible for sending the activation signal to the motor unit which also recruits these fibers for maximal force to be produced by the muscles. Increased force means more motor units. To recruit these motor units, the demand for force must be high! Due to the amount of force produced and the nature of these muscle fibers to be more explosive, a high amount of volume isn’t necessary and is quite counterproductive. They fatigue quickly and unnecessary volume will extend recovery time.
Type II muscle fibers are the ones that tend to show up well directly under the skin and tend to be in a partial state of muscle contraction. So, if you’re a person or happen to see someone who is lean with rock hard muscle, they’ll typically have a large proportion of these muscle fibers and are better at (or prefer) heavier and/or explosive work.
Type I (Slow Twitch)
These little darlings have the opposite ability of our Type II friends. Your Type I muscle fibers are built more for endurance activities and can’t produce nearly the same amount of force. It doesn’t take much effort to recruit these motor units. People with predominantly Type I fibers have inefficient nervous systems and lack the ability to produce powerful muscle contractions. Women tend to have 27-35% more Type I fiber area relative to total muscle fiber area than men.
What Type of Muscle Fibers Do You Possess?
One way to determine your muscle fiber makeup is to perform the 80% Test. The results aren’t 100% accurate, but it can provide some clues as to what your body is currently capable of in the gym. Training experience can also play a factor.
|Reps at 80% of 1RM||Muscle Fiber Type|
|3 to 4||Fast-twitch very dominant|
|5 to 6||Fast-twitch dominant|
|7 to 8||Mixed intermediate/Fast-twitch|
|9 to 11||Mixed intermediate/slow-twitch|
|12+||Slow twitch dominant|
Once you have a better idea of your muscle fiber type, the next steps for building muscle become clearer.
- If you’re fast twitch dominant or mixed intermediate/fast-twitch, and enjoy heavy and/or explosive work, the best hypertrophy approach that won’t hamper recovery needs to be determined.
- If you’re mixed intermediate/slow-twitch or slow twitch dominant, and want to improve your physique, your training will have to include methods that help produce HTMUs and the hypertrophy approach will have to change over time as those Type I muscle fibers begin to take on the traits of Type II’s.
Reps Per Set
Since we’re looking for muscle growth specifically and not concerned about increasing strength, avoid the 1-5 rep range. Most men do well in the 6-10 rep range for gaining size and maintaining strength. On some exercises, 5 reps can do the job but you shouldn’t go to absolute failure. For example, heavy squats using a 4 x 5 rep scheme can work well if the eccentric portion of the exercise is accentuated properly. The eccentric portion of a movement is the main stimulus for growth and there’s evidence that maximal eccentric actions will preferably recruit fast twitch muscle fibers.
For that reason, 5-10 works great for most men.
The muscle fiber makeup in most women makes the rep range for muscle growth slightly different. Due to the higher amount of Type I fibers, most women should stick in the 6-12 rep range. Why? You’ll need an extra rep or two to help generate HTMUs.
Side bar: Most people will benefit from performing isolation exercises in the 10-15 rep range for the delts, glutes, calves, and abs.
Volume Per Week
For guys who want to train their chest or the girl who wants to train their glutes every fucking day, this one’s for you.
Last year, researchers conducted a study to compare the effects of different volumes of resistance training on muscle performance and hypertrophy in trained women. 40 women with at least 3 years of previous training experience participated for 24 weeks and were divided into groups that performed five (G5), 10 (G10, 15 (G15), or 20 (G20) sets per muscle group per session. A 10RM test was performed (bench press, lat pulldown, 45-degree leg press, and stiff legged deadlift) to establish a baseline for strength gains. Muscle thickness was measured using an ultrasound at the bicep brachii, triceps brachii, pectoralis major, quadriceps femoris, and gluteus maximus. All groups trained to momentary failure each set. Each muscle group was trained once a week and all sessions were supervised.
After 24 weeks, there were no differences any 10RM test between the G5 and G10 groups. The G5 and G10 groups showed significantly greater 10RM increases than the G15 and G20 groups in every test except for the bench press (G10 and G15 showed no difference).
The results from each muscle thickness test displayed zero differences between the G5 and G10 groups. Both groups had greater results than the G15 and G20 groups.
For you, this means that using 5-10 sets per muscle group each week is enough to stimulate muscle growth if you’re training to muscle failure. More than that appears to be a waste of your time and energy.
Therefore, train hard and don’t leave any reps in the tank before form begins to break.
Barbalho, Matheus & Coswig, Victor & Steele, James & Fisher, James & Paoli, Antonio & Gentil, Paulo. (2018). Evidence for an Upper Threshold for Resistance Training Volume in Trained Women. Medicine & Science in Sports & Exercise. 51. 1. 10.1249/MSS.0000000000001818.
Thibaudeau, Christian. High-Threshold Muscle Building. F. Lepine, 2007.
Miller, A.E.J., MacDougall, J.D., Tarnopolsky, M.A. et al. Europ. J. Appl. Physiol. (1993) 66: 254. https://doi.org/10.1007/BF00235103
Mitchell, C. J., Churchward-Venne, T. A., West, D. W., Burd, N. A., Breen, L., Baker, S. K., & Phillips, S. M. (2012). Resistance exercise load does not determine training-mediated hypertrophic gains in young men. Journal of applied physiology (Bethesda, Md. : 1985), 113(1), 71–77. doi:10.1152/japplphysiol.00307.2012