According to gym lore, the sweet spot for building muscle is performing 8–12 repetitions per set. It was one of the first rules of building muscle I learned and gym-goers across the world would agree.
Where did this belief come from?
Research and experience.
Well, that seems like a solid foundation, doesn’t it? Here’s the think about research: it changes.
The traditional repetition continuum proposes the following:
A low repetition scheme with heavy loads (from 1 to 5 repetitions per set with 80% to 100% of 1-repetition maximum (1RM)) optimizes strength increases. A moderate repetition scheme with moderate loads (from 8 to 12 repetitions per set with 60% to 80% of 1RM) optimizes hypertrophic gains. A high repetition scheme with light loads (15+ repetitions per set with loads below 60% of 1RM) optimizes local muscular endurance improvements.
A recent study challenges this continuum. When I say study, I am referring to a review paper. The authors, led by renowned exercise researcher Brad Schoenfeld, examined 99 research papers to get an updated understanding of building muscle (known as hypertrophy).
The paper dives into the strength and endurance rep schemes, but I will focus on hypertrophy. The graphic at the end provides a summary of the findings for strength, hypertrophy, and endurance.
Is 8–12 the magic range?
In short, no.
The traditional hypertrophy range of 8–12 reps is not superior to other rep ranges. However, it is not the magic of the number of repetitions, rather the difficulty of the set that matters most.
More research shows low load groups — often less than 60% of your one-rep max — can achieve equivocal strength and hypertrophy gains when intensity is matched. To build muscle, you need to perform resistance training to fatigue levels at or near failure.
Focus on total volume, not within set volume
When it comes to building muscle, volume is king. The more you exercise the bigger you will get. It’s about the total number of sets and reps, not reps within the individual sets. Completing 20 sets of five reps will be superior to three sets of 12.
Let me be clear, you do not have to lift 2 hours a day, 6 days a week to build muscle. People often confuse results with optimal results.
If you train hard, you will build muscle. If you want to maximize your personal potential, you need to consider diet, sleep, stress, and the nuances of training.
Let’s go back to the original research that led us to the development of the hypertrophy zone.
Original studies comparing different rep ranges showed greater anabolic hormone increases in participants who completed the hypertrophy range. These short-term adaptations don’t translate into differing amounts of hypertrophy though. The theory was combined with experience in the gym and the hypertrophy range was born.
Since then, many studies have shown equal amounts of muscle development for moderate and high rep ranges, provided the intensity was matched.
Studies that show different levels of hypertrophy when comparing high and low load training often fail to consider fatigue. Calculations are made when the trial is developed to best guess an appropriate intensity. Oftentimes, the low load group — which is high repetition — fails to hit fatigue.
If you are in the elderly category — over the age of 59— you may even have a better response to light load training than heavy load. Keep in mind, as you age, weight-bearing activity becomes vital for bone health. Building muscle is great, but there are many other goals and health benefits of exercise.
You can do too much
Since volume, not load, is the most important variable for hypertrophy, heavy load-high volume training may not be optimal. The combinations increase the risk of overtraining.
Rest between sets and between sessions must be considered, too. You should rest long enough to recover and continue working at a given rep range. Typically, strength work (less than 6 reps) requires 3–8 minutes of rest between sets, while hypertrophy work requires 1–2 minutes.
While you rest, your muscles replenish ATP — the energy currency of the body. The more you rest, the more you replenish, the high the intensity of exercise you can perform. Rep ranges and rest times will vary.
Once again, the key is you are working at or near failure every set.
Is there a new hypertrophy range?
More of a threshold instead of a range.
The image above (click the link for larger text) summarizes the findings of the Schoenfeld article.
Schoenfeld suggests a minimum threshold of 30% of 1-rep-max is needed for optimal levels of hypertrophy. If your bench press is 200 pounds and you want to use it to develop muscle, keep the weight about 60 pounds. For there, the key is bringing each rep close to or at failure (please have a spotter for failure exercises).
If you want to maximize hypertrophy, you must take into account diet, sleep, and stress. Your training program needs to be on point as well, considering your training age, capacity for recovery, time available to train, and many other factors.
In the end, building muscle comes down to working hard in the gym. Don’t worry about staying in a special rep range. The intensity and overall volume are far more important.