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The hypertrophy spectrum: optimal reps for muscle growth

Endlessly doing 12 reps won't cut it

Want to grow your muscles as big as possible? Just go for the tried and proven classic, right? 4 sets of 12 reps, four or five exercises muscle group. Most bodybuilders and #fitgirls have been doing this for years, but the question is: are you really maximizing muscle growth when training in this manner?

"This generally makes chasing a focus on getting stronger a pretty safe bet when talking muscle growth."

When considering the latest research, the most important ‘stimulants for growth’ are usually categorized as: (1) mechanical tension, (2) muscle damage and (3) metabolic stress. In layman’s terms: (1) lifting heavy, (2) doing plenty of sets with plenty of variation, and (3) chasing the burn/pump. For optimal growth, you therefore need all three. Another way to put it: you can grow a muscle while doing anything from 1 repetition (high mechanical load) up to, say 30 reps (high volume and metabolic stress). Important to keep in mind, however: mechanical tension appears to be the most important drive for muscle growth. Not very surprising, if you consider what the usual weightlifter or powerlifter looks like. They tend to be pretty muscular. This generally makes a focus on getting stronger a pretty safe bet when talking muscle growth. But mind you: just working in the heavy ranges means you’ll be missing out on growth that is to be reaped from training with higher volumes and repetitions.

So what is it that makes classic rep schemes like 4x12 this popular across gyms and galaxies? Well, because it kind of covers all three bases. Weights are moderately high (about 70-75% of your one rep max), there’s quite some volume going on, and the burn and pump are there. Another popular example would be 5x5 (five sets of five reps); which scores a little higher on the mechanical tension scale, but is obviously much lower in volume and metabolic stress. Again a nice cocktail, nonetheless. These examples are however just two loading parameters, kind of an average of all factors needed for growth, and to keep progress going, you need variation and novelty.

The question then is: how do you optimally use this low to high spectrum to your advantage? One way to cover the whole spectrum would be to periodically train within a certain rep range, for example: high reps for a few weeks, medium reps for a few weeks, low reps for a few weeks, and repeat. Personally I am not a huge fan of this approach, because one tends to lose too much capacity in the other side of the spectrum that’s currently not being trained (like losing work capacity when exclusively training with low repetitions), which may hamper long term progress. Also, I have found many complex exercises to not be very suitable for very high rep work (imagine doing sets of 30 deadlifts), while I find many isolation or unilateral exercises to not be suitable for heavy work (ever tried doing a 3 rep max walking lunge?).

"I prefer to program more of a continuing hybrid"

Personally, I prefer to program more of a continuing hybrid, with stacking plenty of mechanical tension and metabolic stress in one single training session, while inducing plenty of muscle damage. As an example: when doing four exercises for a muscle group, an easy way to cover multiple ranges would be to do your 5x5, 4x8, 4x12 and 3x25 all in one go. In the case of training the glutes, this could mean doing something along the likes of: 5x5 squats, 4x8 hip thrusts, 4x12 lunges, and 3x25 cable kickbacks.

In the end, there are multiple ways to make this work, but just remember: sticking to one zone too much means you’re likely missing out on sweet gains.

Good luck!

Bryan Wolters

MSc. Human Movement Sciences, former powerlifter, and current trainer at Vondelgym Amsterdam.

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