In principle, it doesn’t matter in which rep range you train for muscle growth. After all, it’s all about the stimulating repetitions at the end of the set. They cause the mechanical tension required for muscle growth. Although for practical reasons it is best to train in the range of 6 to 20 repetitions. Does it nevertheless make sense to load a muscle group in different rep ranges, both low and high?

Key points:

1. Training for muscle growth is mainly about the effort you make, or the extent to which you train a set until muscle failure (also called relative intensity). For optimal muscle growth it is necessary to train close to muscle failure. To avoid a disproportionate amount of fatigue, keep one or a few reps ‘in the tank’ (usually 1-3 Reps In Reserve).

2. The load (absolute intensity) is less important. In principle, you can therefore optimally build muscle with both light and heavy weights. But for practical reasons it is best to train in the range of 6 to 20 repetitions.

3. Still, you may be missing out on a bit of muscle gain if you don’t also do some work outside of that rep range (both sets of 3-6 and over 20 reps). This is because you may address different signaling pathways for muscle growth, optimize different types of muscle growth (myofibrillar and sarcoplasmic hypertrophy), and/or optimally stimulate all types of muscle fibers. Low rep ranges for pure strength also make you stronger and that in itself may also be beneficial for building muscle mass.

4. To date, two direct studies have been conducted into the effects of training in different rep ranges. One of them shows a significant positive effect on muscle growth.

5. As a beginner or intermediate bodybuilder, it is normally sufficient to stay in the traditional range of 6 to 20 reps. If you’re more advanced, you may be able to spark new muscle gains by doing some sets in the ranges of 3-6 and 20+ reps as well.

6. Incorporate different rep ranges into one training program (ie no block periodization). Keep doing 60-70% of that program in the traditional range of 6 to 20 reps. You will probably get the best results if you do different rep ranges in the same workout.

MECHANICAL TENSION

Not so long ago, it was thought that muscle growth must involve three mechanisms: mechanical tension, metabolic stress, and muscle damage. It now seems that the latter two are rather a by-product of training: you have to create mechanical tension and that also causes some metabolic stress and muscle damage. See also our article about it.

Mechanical tension is the fatigue that arises in a muscle by doing several contractions in succession with a certain weight. The greater the fatigue, the slower the contractions, the greater the growth stimulus. That’s why those last reps in a set are so important for muscle growth; one also speaks of stimulating, or effective repetitions. If you stop a set long before muscle failure, you will never get those stimulating reps and therefore you will not achive hypertrophy.

THE ROLE OF EFFORT (RELATIVE INTENSITY)

A lot has already been said and written about repranges (the absolute training intensity, or the load). And eventually we found out that it doesn’t really matter what weight you train with, as long as you create enough muscle fatigue (so stimulating repetitions) with it ^[ i ] . If you meet this condition, you can build maximum muscle in the range of 1 to 30 repetitions, working more on your maximum strength in the lower repanges and more on your strength endurance in the higher reps.

There is no hypertrophy range. Anything between 1 and 30 reps is sufficient for maximum muscle growth. Source: Menno Henselmans.

In other words: bodybuilding is all about the effort, the effort you make (also called relative training intensity). In principle, 15 repetitions with a light weight yield just as much muscle growth as 6 repetitions with a high weight, provided that both sets are trained to near muscle failure. For light weights, a lower limit of 30%1RM ^[ ii ] applies though.

So remember:

effort > load

We said “close to muscle failure” because it’s best to stay away from muscle failure in most sets. Training all your sets indiscriminately until the hole results in a disproportionate amount of fatigue, so that you end up doing fewer sets and therefore less stimulating repetitions on balance. If we look at the figure below, then you train at least ‘Hard’, sometimes ‘Hard AF’ and only once to ‘Failure’:

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Effort is usually expressed in Reps In Reserve (RIR), the number of reps you stay away from muscle failure. As a rule, that’s about 1-3.

THE IMPORTANCE OF SETS

Because one set, even if you train it close to muscle failure, only produces a limited number of stimulating repetitions (about five), you have to do several sets per muscle group to really grow. An average bodybuilder needs somewhere between 10 and 20 sets per muscle group per week to grow, with a maximum of 5-10 sets per workout. This taking into account an effort of 1-3 RIR on average.

The figure below summarizes all this.

You create a growth stimulus by doing enough sets and by making sufficient effort per set, so by training until (near) muscle failure.

THE IDEAL REPRANGE

However, it appears in practice traditional reprange of 6 to 20 (or 6-15) repetitions best work for muscle growth. Why is that?

When training with very light weights, in very high rep ranges (for example, sets of 30 repetitions), there is relatively much central and cardiovascular fatigue and this can cause you to stop a set even though you are still far from muscle failure. That while with light weights, for optimal muscle growth, it may be necessary to train to muscle failure, while with heavy weights you can safely stay away from it ^[ iii ] . That in itself is also a disadvantage, because training to muscle failure involves a disproportionately large training load.

Very heavy weights, on the other hand, carry an increased risk of injury. In addition, with very short sets (< 6 reps) you may miss stimulating reps, which means that you should do more sets.

Most coaches recommend doing compound exercises such as presses and rows with slightly heavier weights (6-10 reps) and isolation exercises, such as biceps curls, with slightly lighter weight (10-20 reps). The latter mainly because you are more vulnerable if a muscle group is working on its own in an exercise.

6 to 20 repetitions therefore seems to be the ideal rep range to create mechanical tension and thus stimulating repetitions.

ARGUMENTS TO (STILL) USE MULTIPLE REPRANGES

However, you might also need to do some work in very high rep ranges (20-30 reps) and very low rep ranges (< 6 reps). Because science is gradually giving several arguments as to why this could lead to extra muscle growth, especially with more advanced natural bodybuilders, for whom it is becoming increasingly difficult to achieve muscle growth.

1. DIFFERENT SIGNALING PATHWAYS FOR MUSCLE GROWTH

A new study finds that different weights (and thus different rep ranges) address different so-called muscle growth signaling pathways ^{[ iv ][ v ]} . These pathways arise from chemical signals resulting from strength training and food availability, and lead to the growth response necessary for muscle growth, particularly in the form of increased muscle protein synthesis.

In the study in question, leg press training with high weights (85%1RM) activated a different muscle growth signal than training with medium weights (65%1RM). Both training protocols used the same amount of effort and led to similar increases in muscle protein synthesis. We already knew the latter. But the fact that muscle growth in both cases follows different paths may provide new insights. After all, if your body has adapted to a certain load and rep range, it may still be sensitive to a different load and rep range, even if the effort is equivalent. Admittedly, this is still very speculative.

2. DIFFERENT TYPES OF MUSCLE GROWTH

If you train in higher rep ranges, there is more accumulation of metabolites, including lactate (the acid residue of lactic acid) and therefore more metabolic stress. Most metabolic stress occurs during sets that last between 20 seconds and 2 minutes.

As mentioned, we now know that metabolic stress is more of a by-product of training than a prerequisite for muscle growth. After all, by far the most important condition for muscle growth is mechanical tension. Yet we should not write off metabolic stress as a mechanism for muscle growth.

According to new research, metabolic stress could affect a specific form of muscle growth. There are two types of hypertrophy: myofibrillar and sarcoplasmic hypertrophy. And possibly metabolic stress has a positive influence on the second kind.

In myofibrillar hypertrophy, the muscle grows because the number of myofibrils increases. Myofibrils are supposedly the building blocks of muscle fibers. An increase in the number of myofibrils therefore causes a muscle fiber to grow larger. Myofibrils, in turn, are made up of contractile elements (sarcomeres), which allow the muscle to contract. An increase in the number of contractile elements is mainly associated with an increase in maximal strength and training intensity.

In sarcoplasmic hypertrophy, muscle growth occurs due to an increase in the sarcoplasm, the sheath of the myofibrils. This form of hypertrophy is mainly associated with an increase in strength endurance and training volume.

Sarcoplasmic and myofibrillar hypertrophy. The third, most common possibility is missing from this image, namely the growth of both the sarcoplasm and the number of myofibrils. (Source: Zatsiorky/Science and Practice of Strength training via Lyle McDonald)

There is still a lot of uncertainty and therefore controversy about these two forms of muscle growth. It is often thought that they occur simultaneously and that you cannot train specifically for one type of muscle growth. The sarcoplasmic hypertrophy would then be mainly intended to create space for larger muscle fibers, as a result of the myofibrillar hypertrophy. Others claim that you can train specifically for a certain type of muscle growth. Myofibrillar hypertrophy would mainly occur with a lot of mechanical stress, sarcoplasmic hypertrophy especially with a lot of metabolic stress.

The latter theory is gradually gaining support from a scientific perspective, as in a study by Haun et al. from April 2019 ^[ vi ]. The scientists examined the effects on muscle growth of a six-week training program with a relatively high volume and low intensity on young, experienced strength athletes. To be precise: many repetitions with fairly low weights (60%1RM) and a fairly low relative intensity (average 4 RIR). After the six weeks of training, a muscle biopsy was taken to determine exactly how the muscle growth had taken place. What turned out? The size of the muscles had increased, but not due to the growth of myofibrils. Thus, the training regimen did not induce myofibrillar, but only sarcoplasmic hypertrophy. Due to the low intensity, the myofibrils were not stimulated enough to allow them to grow, but the high metabolic stress still resulted in muscle growth due to the increase in the sarcoplasm.

A quite revolutionary discovery, according to scientist and hypertrophy expert Brad Schoenfeld, who in a fairly recent review article spoke of a lack of direct evidence for the effects of metabolic stress on muscle growth ^[ vii ] . Haun and co’s research appears to be the first convincing direct evidence. And also a first proof that sarcoplasmic hypertrophy can also occur without myofibrillar hypertrophy taking place. In response to the research, Schoenfeld tweeted:

If you had asked me several months ago, I would have dismissed that “sarcoplasmic hypertrophy” occurred to any meaningful extent in the absence of contractile growth. This study has me reconsidering my opinion. ^[ vii ]

It is unclear whether training with very heavy weights and few repetitions, ie the powerlifting style, then stimulates ‘extra’ myofibrillar hypertrophy.

Metabolic strength training
The study was also fodder for author Lyle McDonald, who wrote a hefty piece about it on his site. His tentative conclusion is that for maximum muscle growth, bodybuilders should also do some training in a more metabolic style, in addition to training in the traditional, more mechanically oriented style. In short, go purely for the ‘muscle pump’ every now and then.

Coach Mike Israetel also sees metabolic strength training as something you could add to your ‘regular’ strength training (mechanical strength training, so to speak) to achieve extra muscle growth in a different way ^{[ ix ][ xiii ]} . Think of doing supersets, circuits and sets with an absurd amount of repetitions. Because of the great acute fatigue that these types of exercises cause, they are best done at the end of your workout. Why people also speak of metabolic finishers.

Metabolic strength training is also often used to combine muscle building and fat loss. However, bodybuilders, especially intermediate and advanced, are better off focusing on one goal at a time.

3. DIFFERENT TYPES OF MUSCLE FIBERS

There are two types of muscle fibers: type I (slow-twich) and type II (fast-twitch). The main difference is the speed at which they contract. The slow contracting type I fibers are basically involved in endurance efforts and the fast contracting type II fibers in explosive and short power efforts.

The ratio between the type I and type II fibers is individually determined and can really vary greatly from person to person. Those who have relatively many type I fibers will be able to excel more easily in endurance sports, such as marathon running, while many type II fibers mean that you can sprint better, for example. As a bodybuilder, you also benefit the most from type II muscle fibers, as they have the greatest muscle growth potential.

Logically, it is often thought that type I muscle fibers in strength training respond better to sets with many repetitions and type II muscle fibers to short sets. Does this mean that you should target the same muscle group with both light and heavy weights? And that you would therefore miss out on muscle mass if you only do sets of 10 repetitions, for example?

Unfortunately, we still cannot say for sure. Coach, researcher, and author Greg Nuckols delved into the matter several years ago and came to the following conclusions:

Most muscles have a fairly even distribution of type I and type II muscle fibers. But there may be muscles in which one of the two types is dominant.
However, there is no (working) practical test to determine whether a muscle contains a dominant muscle fiber type. Also, how many reps you can do with a certain percentage of your 1RM is not a reliable indication, contrary to what some YouTube coaches claim.
Whether you should use different rep ranges to target different muscle fiber types remains unclear: the results of scientific research on this are quite varied.

The article by Nuckols dates from 2016. We can now add a review by Brad Schoenfeld from 2018. But he also concludes:

There currently is not enough evidence to make a firm conclusion regarding changes that occur at the muscle fiber level with different loading schemes. ^[ x ]

4. STRONGER IS BETTER

Although in theory you can achieve optimal muscle growth with both heavy and light weights, according to coach Menno Henselmans you might still be wise to do some pure strength training as a bodybuilder, that is, sets in the range of 3 to 6 repetitions. New studies suggest that as a strong bodybuilder you (still) have an advantage. And to get strong, it’s best to train in low rep ranges.

One of those studies used block periodization: 5 weeks of bodybuilding training, followed by 3 weeks of strength-oriented training. That is a possibility, but other studies have shown that it is not the most effective method. Henselmans advises to put those different rep ranges in one training cycle, preferably even to do them in the same training. Then you start your training with a few sets in the 3-5 rep range, for example, and then switch to the more usual rep ranges (6-20). According to Henselmans’ colleague Mike Israetel, however, you should not do too many different rep ranges within one training session, because that may cause unnecessary fatigue ^[ xiii ] .

Train for strength with sets of at least 3 repetitions. To this end, you can optionally apply the inverted pyramid model, where it slightly lowers the weight for each subsequent set.

DIRECT EVIDENCE

The arguments may hold true, but is there direct evidence for the alleged positive effect of using different rep ranges in one training program? Not that much yet: to our knowledge, only two studies have been devoted to it so far.

SCHOENFELD ET AL.

First, a study by Brad Schoenfeld himself, from 2015 ^[ xi ] . In it, 19 trained young men were split into two groups. Group 1 trained for eight weeks, three times a week, exclusively in the range of 8 to 12 repetitions. Group 2 did the same but in three different rep ranges: 2-4 RM per set on day 1, 8-12 RM on day 2 and 20-30 RM on day 3. Afterwards, both groups had significant increases in muscle mass, maximal strength and strength endurance. Group 2 did, however, note slightly more muscle growth in the biceps and triceps, slightly more strength increase in the bench press and slightly more increase in strength endurance in the total upper body.

Schoenfeld concludes that you can achieve significant muscle growth with training in one rep range as well as in multiple rep ranges. However, we cannot ignore the fact that the protocol led to slightly better results with different repranges, albeit to a limited extent.

FISCHETTI ET AL.

In the second, Italian study, from 2020, the results were compared between the results of high weights (3-5 repetitions), low weights (up to muscle failure at 30%1RM), and of both high and low weights (the combination group), during one training program that included squats and leg extensions ^[ xiv ] . A total of 37 people took part. Muscle growth was measured based on thigh circumference.

What turned out? In the combination group, the circumference had increased twice as much as in the other two groups. In addition, the participants in this group had lost significantly more fat than those in the other groups (in short, a convincing body recomposition had taken place). Finally, they managed to increase their 1RM strength as much as the participants in the high-weight group, while those in the low-weight group had to lose some strength.

The conclusion of the researchers:

Resistance training performed simultaneously in different load areas optimizes muscle hypertrophy. These data underline both the reactivity of skeletal muscle to mechanical load alterations and the importance of metabolic stress as a necessary factor for increasing muscle volume. ^[ xiv ]

In short, they attribute the results to the three arguments above, although it is not clear which of them is decisive. Perhaps that is the metabolic stress, which fuels sarcoplasmic muscle growth.

It is the first study in which the possible positive effect of multi-reprange training is so clearly apparent.

CONCLUSION

In principle, you can optimally build muscle with both light and heavy weights. But for practical reasons, it’s best to train in the range of 6 to 20 reps – for example, compound exercises with 6-10 repetitions and isolation exercises with 10-20 repetitions.

Still, you might be missing out on a bit of muscle gain if you don’t also do some work outside of your fixed rep range, for example sets of 3-6 reps on one side, and sets of 20-30 reps on the other end of the spectrum. This is because you may address different signaling pathways for muscle growth, optimize different types of muscle growth (myofibrillar and sarcoplasmic hypertrophy), and/or optimally stimulate all types of muscle fibers. Low rep ranges for pure strength also make you stronger and that in itself may also be beneficial for building muscle mass.

Scientific evidence for these cases is as yet limited. Direct evidence for the possible need for variation in rep ranges is also scarce for the time being.

The following applies: if it does not help, then it does not harm. Doing an exercise in two different rep ranges every week will give you muscle gains anyway, as long as you apply progressive overload in both rep ranges over time .

PRACTICAL ADVICE

As a novice or intermediate bodybuilder, traditional training protocols will normally allow you to achieve optimal results. That is, you do your exercises in the range of 6 to 20 repetitions, with a distinction between compound exercises (mostly 6-10 repetitions) and isolation (10-20 repetitions). All this taking into account sufficient effort, ie you train close to muscle failure, but usually not completely. If you do not achieve enough results, it is probably due to your training volume (too many or too few sets), your recovery and/or your diet. And not the fact that you don’t train in different repranges.

If you are more advanced, you may find it difficult to achieve muscle growth. In that case, it may be worth doing multi-reprange training. That is, for each muscle group (or, if desired, only for certain muscle groups) you also do some work outside the range of 6-20 repetitions, so both 3-6 and let’s say 20-40 repetitions. The majority of your training, roughly 60-70%, you nevertheless continue to do in the traditional 6-20 range. Your entire training program will look something like this:

Example of variation in rep ranges in a training program. (Source: Stronger by Science)

Some research suggests that you get the most benefit from different rep ranges if you do them in one workout. For example, start with pure power (3-6) and end with some metabolic work (>20). This way of training may cause more fatigue, so keep that in mind when you recover.

We do not recommend spreading different repranges over different mesocycles (block periodization), so that you train one cycle in a high reprage and the other in a low one. The disadvantage of this method is that you may lose adaptations and therefore also muscle growth that you had achieved with a different rep range (which you then no longer use for a longer period of time). You can prevent that by continuing to train for maintenance in that other rep range. So you can safely focus on a certain rep range during a block, but make sure you also continue to do some work in other rep ranges.

IN SUMMARY

1. Training for muscle growth is mainly about the effort you make, or the extent to which you train a set until muscle failure (also called relative intensity). For optimal muscle growth it is necessary to train close to muscle failure. To avoid a disproportionately large training load, keep one or a few reps ‘in the tank’ (usually 1-3 Reps In Reserve).

2. The load (absolute intensity) is less important. In principle, you can therefore optimally build muscle with both light and heavy weights. But for practical reasons, it’s best to train in the range of 6 to 20 repetitions.