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The new approach to training volume

Der neue Ansatz zum Thema Trainingsvolumen

A brief overview

  1. Studies with a wide range of different populations have shown that muscles grow at a wide variety of different repetition ranges.
  2. When training programs are matched by their number of sets, they generally result in very similar levels of muscle growth, even when they involve very different training volumes.
  3. However, gains in strength and muscle endurance are very closely related to the repetition range used.
  4. At least when we are talking about hypertrophy-based training, it is more useful to define training volume as "number of hard sets per muscle group" rather than "sets x reps x weight".

The way in which exercisers usually calculate their training volume (sets x reps x weight) has some significant disadvantages

  1. Inherently heavier exercises seem to be better than lighter exercises (e.g. you can accumulate more volume with leg presses than you can with squats, and with squats this accumulated volume is higher than with front squats).
  2. Training with a lower percentage of your 1 RM weight almost always seems to be superior to training with a higher percentage (3 x 10 with a demanding weight means more volume than 3 x 3 with a demanding weight).

Simply counting the hard sets is a much simpler way to accomplish the same purpose without giving certain exercises or load patterns an advantage over others.

For strength and muscle mass it's a simple question of how many heavy sets (80-85%+- of 1RM weight) you perform, for muscle mass and muscle endurance it's a question of how many relatively light sets (65% of 1RM weight and below) you perform and for a mix of both it's a question of how many hard sets you perform in the medium intensity range.


For as long as I've been training, I keep hearing the recommendation that 1 to 5 reps should be used to build strength, 8 to 12 reps to build muscle mass, and 15 to 20 reps to build muscle endurance.

The concept of myofibrillar hypertrophy and sarcoplasmic hypertrophy, which is commonly used to explain the differences between strength athletes and bodybuilders, states that heavier weights build contractile proteins in the muscles (myofibrillar hypertrophy) and that higher repetition numbers (8 to 12) focus more on increasing the sarcoplasm (fluid) in the muscles.

However, the concept of sarcoplasmic hypertrophy is not supported by the scientific literature and strength differences are more easily explained by other concepts that are actually scientifically supported.

The American College of Sports Medicine recommends that novice hypertrophy exercisers perform 1 to 3 sets per muscle group with 8 to 12 repetitions each and 1 to 2 minutes rest between sets, two to three times per week. For experienced exercisers, the recommendation for hypertrophy is to use 70%-100% of their 1 RM weight for 3 to 6 sets with varying lengths of rest between sets depending on the goals, at a 4 to 7 day frequency (1). Recommendations for building strength are similar.

However, research in recent years (and decades of successful use of training methods by athletes and bodybuilders) has shown that these recommendations - while likely to work - are only a small part of the overall picture.

More recently, Fisher et al wrote a position paper recommending a maximal intensity of effort on each set (training to instantaneous muscle failure), using a load and frequency appropriate to the exerciser's goals and performing only a single set per exercise (2).

Finally, Brad Schoenfeld published a meta-analysis (a paper that summarizes the results of several studies to find a scheme in the scientific literature) on the different effects of different repetition ranges on strength and hypertrophy.

This meta-analysis compared low weights (<60% of 1 RM weight) with high weights (>65% of 1 RM weight) and found that there was a greater effect on hypertrophy at the higher weights than at the lower weights and that strength gains were much greater in the higher weight group (3).

However, a closer look at the studies analyzed shows that 6 of the 8 studies that examined hypertrophy had the high load groups perform more sets than the lower load groups. If you've studied strength theory, you probably know that more sets stimulate more gains in strength and muscle mass, so this is an obvious confounding variable.

The size principle

Before we can get into the really interesting aspects of the topic, it's important to understand the basic physiology of muscle recruitment.

During any set you perform to muscle failure, your nervous system will recruit the smaller, slower contracting muscle fibers first and only then resort to the larger, faster contracting fibers when the force requirements are met (4).

For example, let's say (using arbitrary numbers to facilitate general understanding of the concept) that I can perform 10 curls with a 25 kilo dumbbell. During my first 3 repetitions, I may only use small/slowly contracting motor units and muscle fibers.

By the beginning of the sixth repetition, the small fibers are already somewhat exhausted and can no longer produce enough force to move the weight and I begin to recruit larger muscle fibers.

After the tenth repetition, all the muscle fibers of my biceps have been recruited and have experienced so much fatigue that they can no longer produce enough force to move the weight, which is why I can no longer perform an eleventh repetition.

In reality, of course, the size principle is a little more complex than this example, but it's enough to explain the basic concept.

But what happens if I use a 12.5 kilo dumbbell instead of the 25 kilo dumbbell and perform 25 repetitions with it until muscle failure? The exact same pattern is repeated.

The same basic pattern also applies when I use a 37.5 kilo dumbbell to perform 3 repetitions to muscle failure.

From a muscle perspective, the same thing happens in all three cases: all the muscle fibers were recruited and eventually something happened that made them less able to produce force.

However, there is some recent EMG research that casts doubt on the fact that the largest/fastest contracting motor units in trained strength athletes are recruited during high repetition sets to muscle failure (5), with several possible explanations for the lower EMG readings at low weights - and furthermore, the size principle has been proven in practice.

It could be that the largest muscle fibers are actually recruited during training with lower weights until muscle failure, but fewer fibers are recruited at the same time, which would result in a lower EMG deflection.

It could also be that trained strength athletes who have trained with certain repetition ranges over a long period of time are able to put more effort into that repetition range (typically over a higher weight) and that if they had trained with lighter weights for a few weeks, they would have learned to put in the appropriate effort here as well.

What causes muscle fatigue?

Fatigue during resistance training is still a shaky concept. However, we know that when a muscle contracts, metabolic waste products are produced. In addition to this, blood flow to and from the muscle is impeded during a contraction or time under tension, resulting in slower removal of these metabolites.

When the production of metabolites is faster than their removal, the concentration of these metabolites in the muscle increases and the metabolites begin to interfere with muscle contraction.

It is also likely that they stimulate the sensation of pain and your brain may interpret this pain as a signal and decide to invest less effort in recruiting motor units.

Whatever is happening is almost certainly a combination of different effects at the muscular and central nervous system level.

This concept is probably best explained by a technique called Blood Flow Restriction Training. Here, a bandage is placed around an arm or leg to reduce blood flow during a set.

When using this technique, the exerciser can only move significantly less weight or perform significantly fewer repetitions with the same weight, but the same gains are achieved as when using heavier weights without reducing blood flow (6).

But why is this concept important? Because, at least at this point, it appears as though the muscle fibers are being recruited and need to experience at least some fatigue in order to grow. Something about this exhaustion process signals to the body that hypertrophy should begin.

I like to imagine that each instance of exhaustion stimulates a small amount of hypertrophy, so that multiple instances of exhaustion - multiple sets to muscle failure - build up a large amount of hypertrophy stimulation.

The. Effects of different repetition ranges on hypertrophy

Now that we have a better understanding of some general background information, we can examine the effects of different repetition ranges on muscle growth.

First, we need to find studies that control for effort per set so that we don't have a group that doesn't perform their sets to muscle failure (and thus doesn't recruit and exhaust all fibers) while another group performs their sets to muscle failure.

Next, we need studies that control for training volume (weight x repetitions) or number of sets. If a study has one group perform only one set to muscle failure and another group perform 10 sets to muscle failure, then we won't be able to tell if differences in strength and hypertrophy are related to the repetition ranges used or the different number of sets.

Fortunately, we have a reasonable number of studies that have done what we need. I have summarized these studies in the table below. All sets in all these studies were performed to muscle failure.


Controlled factors

Examine rep ranges

Hypertrophy effect

Strength effect

Endurance effect

Weiss et al, 2000 (7, 8)


3-5 vs. 13-15 vs. 25-25

No difference between the groups

Largest increases in the 3-5 RM range, smallest increases in the 25-25 RM range

Not investigated

Campos et al, 2000 (9)


3-5 vs.9-11 vs. 20-28

No difference between 3-5 and 9-11, no hypertrophy at 20-28

Strongest in the 3-5 group

Strongest in the 20-28 group

Alcaraz et al, 2011 (10)

Number of sets

6 in both groups, but one had 30 sec. and one had 3 min. rest between sets

No difference between the groups

No difference between the groups

Not investigated

Mitchell et al, 2012 (11)

Number of sets

3 sets with 30% of 1 RM weight vs. 3 sets with 80% of 1RM weight vs. 1 set with 80% of 1 RM weight

No difference between the groups

Strongest in the 80% groups

Strongest in the 30% group

Schoenfeld et al, 2014 (12)


2-4 vs.8-12

No difference between the groups

Strongest in the 2-4 group

Not investigated

Van Roie et al, 2014 (13)


10-15 vs. 80-100 vs. 60 repetitions with 20% of 1 RM weight, followed by 40% of 1 RM weight to muscle failure

No difference between the groups

Strongest in the 10-15 group and the "strange" group / group 3

Only increased in the 80-100 group

Schoenfeld et al, 2015 (14)

Number of sentences

8-12 vs. 25-35

No difference between the groups

Strongest in the 8-12 group

Strongest in the 25-35 group

If you take a closer look at these studies, several patterns become clear. In the Campos study, the light weights did not produce as much hypertrophy as the heavier weights. However, the light weight group also performed fewer sets than the heavier weight group to achieve a similar volume.

Assuming that load makes no difference (which may be a dangerous assumption, but one that becomes safer when considering all the literature), this seems to indicate that the number of sets may be what determines hypertrophy. However, in the Schoenefeld study from 2014, one group performed exercises with 3 sets of 10 repetitions, while the other group performed exercises with 7 sets of 3 repetitions (again, the volume load was the same for both groups). If the number of sets is what matters, then the 7x3 group should have achieved greater hypertrophy, which was not the case.

If you dig a little deeper, you'll find that the lighter weight group performed a total of 9 sets per week per muscle group to muscle failure, while the heavier weight group performed 21 sets.

If the total number of sets stimulating each muscle is taken into consideration, then it seems possible that 9 sets to muscle failure per week (or less) may have already stimulated the maximum amount of hypertrophy in this training population and that the additional 18 sets performed per week by the heavier weights group contributed little to nothing to additional hypertrophy. The Van Roie study also used volume load instead of number of sets, but saw no difference in hypertrophy.

In the rest of the studies, the number of sets was equalized between the groups and this helped to reveal the pattern: different repetition ranges seem to have the same effects on hypertrophy.

But not only that - these studies looked at untrained, well-trained and even older people, meaning that the similarities in observed hypertrophy hold from all angles.

The next striking pattern is that heavier weights made the study participants better at moving heavy weights, while lighter weights made the subjects better at moving lighter weights, although muscle growth was the same for both groups.

This could be related to a number of factors that have not yet been studied in the scientific literature: neuronal adaptation to specific weights, muscle fiber type specific hypertrophy, aerobic/anaerobic adaptations in muscle fibers, etc. I personally tend to think of this effect as primarily neural in nature, with the actual differences in muscle adaptations probably being rather minimal - but this is just speculation on my part and it remains to be seen what the actual answer is. I believe that lighter weights preferentially stimulate hypertrophy of type 1 fibers when I look at single fiber measurements like the Campos study.

There are a number of studies that have looked at the muscle fiber types of steroid-free weightlifters at the competitive level (15) and steroid-free powerlifters (16) and the ratios of muscle fibers to each other were very similar.

Some other studies have looked at the muscle fiber types of bodybuilders (17, 18), but they were conducted with untested competitive bodybuilding athletes at a very high level and the number of subjects was very small, so steroid use and other factors such as different muscle groups in the different studies make it difficult to draw conclusions.

In addition, none of the studies that examined muscle fiber types were training studies, so the actual effects of specific repetition ranges on muscle fiber types cannot be assessed.

The third striking pattern (based mainly on studies not included in the table above) is that a higher number of sets increases the effects on strength and hypertrophy (19). For example, in the Campos study, the heavier weight group performed more sets than the lighter weight group because the authors wanted to keep the volume equal between the groups and no hypertrophy was observed in the lighter weight group.

However, in several other studies we can observe that even lighter weights stimulate hypertrophy when more sets are performed.

Primary conclusions

What does all this mean? I believe that several basic principles can be derived from these observed patterns.

  1. Based on size principle, we know that the effort of each set must be high enough to recruit and stimulate all fibers. We do not know the exact stimulus threshold for stimulating hypertrophy and there are plenty of people who achieve significant muscle growth without ever training to muscle failure, but in general it is probably necessary to perform the sets at least close to muscle failure.
  2. The repetition range does not matter for hypertrophy (at least for up to 30 repetitions per set for trained people and for up to 100 repetitions per set for untrained people) as long as the effort per set is the same. Muscles appear to grow equally regardless of whether 3 or 100 repetitions are performed to muscle failure. It remains to be seen if muscle growth would remain the same with something like 70% effort in both groups instead of training to muscle failure, but I believe it would.
  3. Strength gains are specific to the repetition ranges used. If you want to get better at maximal strength attempts, then you need to train with weights that get close to that range. If you want to get better at high reps, then you need to train with lighter weights. You can probably get better at both if you use both repetition ranges.
  4. More sets or volume (it's still a little unclear which of these will give you better results, although I tend to favor more sets) will give you better results.

With this information, it's easy to answer the question of why there are differences in strength and muscle mass between strength athletes and bodybuilders. The answer to the question of strength differences lies in the repetition ranges used. Strength athletes generally train more with heavier repetition ranges and many bodybuilders prefer to stay in less injury-prone repetition ranges. However, many bodybuilders also compete successfully in powerlifting competitions by including heavier training in their training program.

The differences in muscle mass are a little more complicated. Personally, I don't think there is much difference between bodybuilders and powerlifters at a similar level. The difference is more of an illusion caused by differences in body fat percentage and a focus on muscles that primarily improve aesthetic appearance vs. muscles that increase strength.

Muscles that both groups train hard, such as legs, back and chest, should be similar in size.

To put it more simply, strength training is bodybuilding and bodybuilding is strength training - whatever rep range you use.

Gaps in the analysis

There are still some concepts that science has yet to investigate to a satisfactory degree. The first is what causes the strength adaptations in specific repetition ranges. Are Type I fibers stimulated at higher repetition ranges? Is the difference based solely on neural adaptations and motor learning? We simply don't know yet.

The second is the level of effort required to maximally stimulate hypertrophy. Do we really have to go to muscle failure or can even low effort sets stimulate some hypertrophy?

In the real world, it looks like even very low efforts can produce some muscle growth, but the question is not yet settled. In addition to this, additional low effort sets could reduce any differences.

Last but not least, and probably the biggest and most important question, is what exactly stimulates hypertrophy. There are several hypotheses, some of which are also supported by science, but in my opinion there is no conclusive answer yet (20). Tension on the muscles themselves could already be enough to stimulate hypertrophy, but when you create tension, you automatically get ischemia and an accumulation of metabolic products.

The pump that occurs during training could also contribute to hypertrophy, but heavy sets with low repetitions do not generate a pump and the hypertrophy during these sets is just as strong as during sets with higher repetitions. An accumulation of metabolic waste products could be the primary stimulator, but there are not many studies that have investigated this yet.

For now, we can only look at muscle growth in a larger context and say that picking things up and putting them down frequently makes muscles grow.


If you look at the history of weight training and bodybuilding, countless strategies have proven successful. However, the most successful of these strategies seem to follow a few basic rules that are similar to what we summarized above: Keep the efforts high, keep the number of sets high and adjust the repetition ranges to your goals or whatever keeps you motivated and progress should not be a problem.




From Nathen Jones

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