One of the points that conventional strength & conditioning guidelines seem to have gotten wrong is the idea of the repetition continuum.

Specifically, the idea that it exists at all.

Briefly, it argues that lower reps (heavier weight) build strength, moderate reps (moderate weight) build muscle, and higher reps (lighter weight) build muscular endurance. Furthermore, it argues that you can preferentially target one of these adaptations over the other.

There are three papers [1,2,3] from the mid to late 1900s that this idea is originally based off of.

This idea was quickly accepted as truth, and it has been perpetuated for quite some time.

However, since that time, much more evidence has come out on the subject.

The picture that has been painted is much different than what was previously thought.

Schoenfeld et al [4] published a review article explaining these updates in 2021.

This article will explain their findings, explain what you actually need to focus on (it’s not how many reps you do in a set), and provide some more practical context that you may find helpful.

The big change

To reiterate, previous theory states that you can preferentially target specific muscular adaptations by working within specific repetition repetition ranges.

In short, what is now understood is that you can’t really target one specific muscular adaptation (strength, hypertrophy, muscular endurance) at a time, and you can improve all of them with a very wide range of repetitions.

Hypertrophy

Hypertrophy refers to the growth of a bodily tissue. In this case it is referring to growth of muscle.

Classically, moderate reps were seen as the rep range that preferentially stimulates hypertrophy as opposed to strength or muscular endurance.

As a side note, “moderate reps” may mean 6-12 reps, 8-12 reps, or something similar. It varies slightly depending on your source, but assuming somewhere in that ballpark is good enough.

What the research shows now is that you can build the same amount of muscle using anywhere from 5-30 reps, as long as your proximity to failure is the same.

In other words, it doesn’t matter if you do 5 reps with 2 reps left in the tank or 15 reps with 2 reps left in the tank. Both orientations will build the same amount of muscle.

The important point isn’t whether 5 reps or 15 reps were done, it is that each set was taken to 2 reps shy of failure.

This further begs the question: how close to failure do you need to get for a set to stimulate muscle growth?

I typically recommend aiming to get 3 reps shy of failure across all working sets.

A 2022 systematic review & meta-analysis [5] suggests that training all the way to failure in a set is not better than getting a few repetitions shy. Anecdotally, going all the way to failure does seem to be much more fatiguing than going just a few reps shy.

The reason I provided a range of 5-30 reps previously is twofold.

To start, using at least ~30% of your 1 repetition maximum (1RM) seems to be the minimum dose that’s required to elicit and muscle growth response.

Second, 5 reps is the lowest amount of reps that has been tested in research so far. It very well may be possible that a set of 2,3 or 4 reps will still do the job, I am just hesitant to say for sure until there are data to support this.

So, the bottom line is this: the specific number of reps you do in a set is not what matters.

Your effort level is what matters.

Focus on that.

Strength

Strength refers to how much weight you can lift on a given exercise.

In much of the research, lower reps (heavier weight) does tend to outperform higher reps (lighter weight) for strength improvement, even when proximity to failure is the same.

However, this tends to be true only when the strength testing in the research is the same movement that was being trained throughout the trial period.

In studies where strength is tested on a different exercise than what was trained during the trial period, the benefits of lower reps tend to be washed out [4]

The reason for this, likely, is that there is a skill component to maximal strength expression.

In other words, to lift your heaviest weight possible requires you to use the most efficient technique possible. People who train with lower reps may get more of this practice than those who train with higher reps- out of necessity.

It is likely that if you compared two people who trained the same movement with one using low reps and one using high reps, and then you gave each person a period of time to practice the skill of performing a 1RM lift, then you would say the same improvement in strength.

So, the bottom line is this: it is probable that the same range of repetitions (5-30) can be used to reliably improve strength over time.

If you are someone who is competing in an event where maximal strength expression is going to be required, such as powerlifting, you may need to use lower reps to ensure you have the skill that you’ll need developed.

However, for everyone else, it seems you can train however you please in regard to repetition ranges.

Muscular endurance

Muscular endurance refers to the ability of a muscle to perform repeated contractions over a prolonged period of time.

Typically, the term “muscular endurance” refers to the specific adaptations that occur within the muscle that contribute to this; whereas the term “endurance” my refer to the muscular adaptations in addition to the adaptations that occur elsewhere in the body that contribute to endurance performance.

The specific adaptations at hand that would contribute to local muscular endurance include increased capillary density and increased mitochondrial density.

Capillaries can be thought of as the exit ramps from your main blood supply to to your muscles, which allow blood, oxygen, and nutrients to be delivered.

Mitochondria are where the majority of energy is produced in your muscles. The more mitochondria you have, the more energy you can produce at any point in time.

In the research, testing how different interventions affect local muscular endurance can be a tricky thing to sort through.

This is at least true when the methods of the study is using high-repetition weight lifting as the means to improve local muscular endurance.

The reason is that if a person is lifting weights within the classic endurance parameters, and they make progress over time, then either the weights used must change or the parameters used change over time as a result of the progress.

In other words, if a person is using 50% of their 1 repetition maximum and they progress over time, then the weight that was their 50% 1RM is now a lower percentage of their 1RM.

That said, the effect of using different repetition ranges on your ability to lift a weight for a high number of reps is the same as the previous two outcomes.

Training with any repetition range, whether it is low reps or moderate reps or high reps, will improve your ability to lift in the higher repetition ranges.

However, for the purposes of yielding the aforementioned adaptations (increasing capillary and mitochondrial density), lifting weights is a highly inefficient means of doing so.

The use of more typical conditioning modalities such as a rower, SkiErg, AirDyne, bike, running, swimming, etc. are far more effective because they are more specific to the adaptations at hand.

The use of very-high-repetition weight lifting is too “in the middle” of resistance training and conditioning for it to be that effective for either goal.

In any case, the recovery needs will be much higher from high-repetition weightlifting than standard conditioning for the purpose of increasing local muscular endurance.

So, the bottom line is this: the use of very-high-repetition weight lifting for the purpose of increasing local muscular endurance should not be seen as good programming.

The idea of pairing this intervention and outcome together should be forgotten.

Practical reasons you may choose on repetition range or another

Despite all that has been said, I do think there are some valid reasons why you may opt for higher or lower repetitions on an exericse.

They just have more to do with practicality than they do with eliciting specific adaptations.

As previously mentioned, getting close to failure at any rep range is more important the specific number of reps you do.

However, with higher rep sets, it may be more difficult to get close to failure because there may be a greater number of painful reps.

In other words, you’ll have to be “in the suck” for a longer of period of time before you get close to failure.

In that sense, lower rep sets may be more opportune.

Furthermore, some exercises just feel better with higher or lower reps.

For instance, movements such as bicep curls and hip thrusts tend to feel better with higher reps; where as squats may feel better with lower reps.

This is largely preference driven, but you get the point.

Conclusion

The take-home points from this article are as follows:

• For the purposes of improving strength or building muscle, anywhere from 5-30 reps will get the job done if you are at least ~3 reps shy of failure

• There are reasons why you may opt for one rep range or another, but they are more practical in nature.

• You should not seek to improve muscular endurance through the use of high repetition weight lifting. Standard conditioning methods applied to the target musculature will be leaps and bounds more effective.