tl;dr:

Research is emerging that suggests the dominant mechanism for muscle growth is mechanical tension.

Creating the appropriate amount of mechanical tension likely hinges on a theory we now call 'Effective or Stimulating Repetitions" -- depending on who you talk to...

Basically, effective reps are the pool of reps (~4-6) done at the tail end of any given set. That point where a certain amount of stress yields a distinct slowdown in the execution of those reps. They can still be done, but the mechanics are altered for various physiologal reasons.

This theory explains why we see similar amounts of muscle hypertrophy with 3 sets of 8, 10, 15 or even 20, 25 or 30 reps. Provided similar amounts of mechican tension are created, then similar amounts of muscle hypertrophy are possible.

It also explains why purposefully slowing down reps (Increasing 'Time Under Tension' [TUT]) via tempo changes, doesn't increase the rate muscle hypertrophy either.

If you want to achieve muscle growth, you will need to train within a certain proximity of momentary muscle failure (the point where you physically cannot complete another rep, not just when you feel you're tired enough to quit). This will permit you to accumulate a minimum amount of mechanical tension or ~5-10 effective reps.

Highlighting that HOW you train is at least equally important, likely even more important than WHAT you train.


Why do people lift weights day after day but not make much progress by way of muscle development?

Why is it so hard to build muscle using exclusively calisthenic training?

Why do people who lift low repetitions but high loads seem to get stronger but not as big as people doing moderate load bodybuilding style training?

Why doesn’t 2 sets of 25 seem as effective for muscle growth as 5 sets of 10?

Today we’re going to talk about a theory that helps explain all of these things while also providing you with an important framework when you’re trying to gain muscle with resistance training.

Effective Reps

AKA ‘stimulating repetitions.’

This is a fairly well supported theory that implies you have to reach a certain level of fatigue and subsequent mechanical tension to properly induce muscle growth.

It’s more specific to people looking to build muscle than anything else and looks something like this:

Stimulating Repetitions
You can build muscle using a variety of set/rep schemes, this models explains why.

Here I’ve graphically shown that the last 5 reps of any given rep range is hypertrophy inducing or ‘effective.’

This means that 3 sets of 15 should be about as effective as 3 sets of 5 if hypertrophy is the objective.

It also highlights an approach to training that alludes many trainees trying to gain muscle:

Proximity to Failure

Research has largely shown that training to failure with high reps and training to failure with low reps yields similar results in hypertrophy.

What’s the common theme then?

Proximity to Failure!

Put a different way, the accumulation of fatigue that leads to bigger and bigger motor units being recruited, which in turn create enough mechanical stress to yield a growth adaptation.

Henneman’s size principle tells us that muscle is activated in ascending size. It’s a key principle in the science of muscle hypertrophy.

Smaller motor units are engaged first and then bigger units kick in as you fatigue. In essence, the same large motor units (and muscle fibres) within a muscle will be engaged whether you lift 3 sets of 5 reps to the same proximity to failure or 3 sets of 15 reps to a similar proximity to failure.

When you train to build muscle, your reps should noticeably slow at some point in the set. This is what seemingly (i.e. best theory we currently have) engages the most muscle into adaptation for size, regardless of the rep range.

The "Right" Proximity to Failure

The appropriate proximity to failure most of the time (in my experience) is reaching what's termed "technical failure."

Watch my Video and Read my Article on Technical Failure Here

In a nutshell technical failure is leaving one to two reps in the tank before reaching a point of absolute failure – or the inability to physically complete another rep. Absolute failure is also termed "momentary muscle failure" or "concentric failure."

Reaching technical failure means that you still reach that slow-down point in the repetition execution, but you do so without reaching a point of grinding or forcing reps. Doing that would cause excessive muscle damage, and hinder recovery.

The idea being that you create a stress that's "just right."

i.e. you do enough work to easily recover from in ~48 hours.

It’s all but been shown as a requirement for muscle building. A follow up article on reps in reserve may provide some further insight but there is a definitely an element to slowing reps that improves hypertrophy outcomes.

*It is however important to note that deliberately or purposefully slowing the reps down is not even remotely the same thing. It has to be a real slowdown in capability brought on by neural changes that indicated mechanical tension is being applied.

For building muscle 3 sets of 5 should be as ‘effective’ as 3 sets of 15. Provided you’re training near your true repetition capacity around technical failure. The point where technique starts to change or feel a bit different.

This provides a pretty good model as to what appears most effective for muscle hypertrophy.

Again, this is not the same thing as purposefully trying to lift slowly or with a slow tempo. That won't help you, if anything, it will be worse for growth because a proper stress is never applied and the weight would have to be reduced substantially to lift slowly.

Why 5 Effective Reps a Set?

Above you see 5 effective reps per set as a generalized recommendation.  Could be 4, could be 6. Maybe it's as high as 8. This is just a rough guide and my best approximation.

Anecdotally I can tell you that you see slower muscle gains at less than 5 reps. This is likely because few people add the required additional sets to achieve the same level of effective reps.

The most intense set-rep scheme you're likely to see for hypertrophy objectives is 5 sets of 5. Which theoretically would yield about 25 effective reps.  

Rarely would you see 8 sets of 3 for 24 effective. It would simply take too long to complete. 5x5 is already time intensive and reduces the total number of training sets you can get through in a given training session by requiring fairly long rest intervals to maintain quality output.

I suspect there is a threshold for minimum effective volume in the range of 5-10 effective reps. And there is likely a point of diminishing returns too, that I'd peg at about 5-6 hard sets per major muscle group per workout. I'm basing that guess on a research paper that once showed 5x10 was as effective as 10x10 for hypertrophy.

The truth being, no one tests volume based on effective reps yet, so I have to guess based on other studies testing the number of sets.

In any case, really high load, low repetition training is not that appropriate for many useful isolation exercises where moderate to high loads are best.

Five appears to be about the sweet spot as the minimum of of reps I'd use for hypertrophy. Yet it is not an absolute number if you're willing to make the difference up with more sets.

No one is doing 5 sets of 3 for the rotator cuff or calves, it just wouldn’t be appropriate. Sets of 5-6 is usually the lowest number of reps you’ll see for isolation exercises for this reason. More often 8-12 reps.

Of course training below 5 reps near technical failure is also really rough. Absolute failure might even be a terrible idea in this rep range.

If you want to build strength – the primary goal of training <5 reps –  you want to be fresh, not fatigued. For strength you likely want to stop a rep or two shy of technical failure. It'd be wise to avoid missed reps entirely.

Time Investment

The biggest potential problem with anything lower than 5 repetitions for muscle gain purposes is accumulating enough effective reps in a reasonable time frame.

It would take 5 sets of 3 to accumulate the same effective volume as 3 sets of 5. Accounting for the necessary rest intervals and the 2 extra sets, it could take 66% more time to get 5 sets of 3 done.

Obviously, if you do that for several exercises it can take quite a large amount of time to get through any given workout. There is an upper limit to how much time most people can spend training.

Also a point of diminishing returns for that time spent. Doing four exercises of 5 sets of 3 will likely be pretty counterproductive at some point.

You could try to save time using a paired set approach like twin pairing training but at this intensity you'd likely struggle with adequate recovery and the number of sets would have to be minimized. Otherwise you'd run into recovery issues.

It’s true you'll get stronger doing 5 sets of 3 but you don’t get a better payoff for muscle hypertrophy than the faster 3 sets of 5. Choose your battles.

On the flip side, doing lots of high repetition work – classified as >12 reps or maybe >15 reps – requires completing a ton of ineffective reps before you get to the effective reps. And the number of sets has to be similar. Again, increasing your time investment.  

3 sets of 20 takes 100% longer to get through than 3 sets of 10. And 12-15 reps in that 20 are likely 'ineffective.' That isn’t to say that 3 sets of 10 is better, just that it requires less time investment.

Note: There are other good reasons to occasionally do sets of 15 (less joint stress, less load required, good for recovery purposes). Just as there are good reasons to occasionally do sets of 3 (more joint stress, improved strength outcomes, bone density, tendon development). However, I personally don't program above 15 reps very often, only in specific situations.

It baffles me when I see hypertrophy programs with 20 or 25 reps – unless it's a calisthenic workout. Choose your battles. The goal is to keep the goal the goal.

If you want to improve fatigue resistance and increase muscular endurance go for it and ramp up the reps. If you want to build muscle, I strongly recommend trying to keep things under 15 reps most of the time.

This will only be a problem for folks trying to use calisthenics exclusively for muscle gain purposes.

Why Calisthenics Don’t Work As Well For Muscle Growth (Generally)

Especially for men...

Once the stimulus of your resistance training drops below 30-40% 1RM (about 30RM or your repetition capacity to do ~30 reps) you see significantly less hypertrophy.

How many air squats can you do after a couple of weeks of training? Hundreds. How many bodyweight lunges can you do after that? Dozens What about push-ups? 30, 40, maybe 50 in one go if you always train for reps?

Many common bodyweight exercises that people try to use on their own at home do not create enough stress. If you can do more than 30-35 reps of an exercise in one shot consistently the stimulus will be too low for continued growth. Despite all the extra work!

Add to that an emerging theory that higher reps likely require a closer proximity to absolute failure (having to stop completely) and you’ve doubled or tripled the perceived exertion – how difficult each set feels.

The result being that the majority of people will struggle to push themselves that close to absolute failure when the sets are so long. Ultimately you make it harder than it needs to be.

Furthermore, we know that the more you train at absolute failure the greater the muscle damage and recovery demands become. Reducing training frequency capacity.

Don’t get me wrong, I love calisthenic exercises. They are excellent for warming up, coordination, keeping people fresh and occasionally maxing out to see what you're made of. But they are deceptively difficult to progress for muscle growth because you need a firm understanding of physics and levers.

I field a lot of questions from young men trying to build muscle with mainly pushups or calisthenics. My answer is always the same:

They will work up until a point but you'll have to deviate from a regular push-up fairly quickly to harder variations. Those variations have a steeper learning curve than using external load.

It's tricky to find useful progressions that keep the reps in reasonable ranges for growth. You have to continually find ways to prevent the reps from getting too high (definitely no more than 30-35, but ideally <15-ish). Next to impossible for most lower body lifts in the long-term but perfectly reasonable or certain challenging lifts like chin-ups.

And of course the time it takes to hit your effective reps can be demotivating with calisthenics training sessions requiring longer time commitments.

Gyms Cost Money

I get it. Gyms can be annoying for some. Inconvenient for others. They cost money. They require travel. It’s free to train with your bodyweight but a tremendous amount of people still end up disappointed. Effective reps explain why.

They spend all this time training a handful of calisthenics movements. They get good at them. They can do a ton of repetitions but they still aren’t seeing the results they’re chasing. It feels like they constantly have to do more – and they do.

The answer is simple: not enough effective reps and too great a time investment. They are improving muscular endurance, and burning some calories which might help make the muscle they already have visible but they are not adding much muscle to what's there.

*If you opt for the calisthenics approach to growth do yourself a favour and invest in some equipment for enhancing your calisthenic training. For instance:

  • Bands (I'm partial to the 41" looped versions for their versatility)
  • Weight Vests (less versatile than bands but awesome for calisthenic training)
  • Plates (for plate loaded push-ups for example)
  • A backpack even, anything you can use to increase the external load on a calisthenic exercise

You can make solely bodyweight work but you will need to educate yourself a bit more than the average gym rat. It will take a lot longer to accomplish than had you added a resistance band to your push-up the moment 30 normal reps was too easy.

Summary

You likely want to spread your work out over multiple sets to maximize the number of effective reps. 2×25 will likely only be ~10 stimulating reps. 5×10 could be 25 effective reps. Same number of reps, big difference in the result.

Generally speaking something between 5–12 reps (maybe 5–15) is where most of a person’s training should lie if muscle growth is the ultimate goal.

It’s the best bang for your buck. The most time efficient rep range, requiring the least number of total work (sets x reps) for reaching an appropriate number of effective repetitions. All without the pain of learning complicated technical exercises for the next year – i.e. 1 arm push-ups are considerably harder to learn than simply adding 1-10 lbs to a lift.

Think of it as the most economical way to train rather than the most ‘effective.’

If you want to build muscle but like lifting heavy, you might want to skew more to the 6-8 rep range.

If you like to feel more of a pump then you might want to skew higher to the 10-15 rep range. They will likely yield similar overall muscle growth but you may enjoy one or the other more or less.

Of course you need an appropriate amount of volume but that might be directly related to volume where the concentric action of muscle (the lifting phase) is actively slowed.

I currently suspect the minimum effective dose to be about ~5-10 effective repetitions per exercise or muscle group – roughly 1-2 hard sets depending on your proximity to failure.

And I'm waiting to see what the point of diminishing returns is but I tend to program 2-5 sets per exercise and shoot for 9-12 "technical failure sets" per week per muscle group.

*Meaning the majority of the training is done within 1-2 reps of failure. Possibly with the last 1-2 sets being right at concentric failure in later stages of a programming cycle or phase.

You’ll periodically want to mix in high low low rep training to improve strength and improve joint stress tolerance (bone mass/ligament/tendon development).

You’ll also want to periodically mix in some low load high rep training to give your body a bit of a break and improve fatigue resistance.

Read “Is It Better to Lift Light Weight or Heavy Ones?

*You may also want to mix in low to moderate repetition/load explosive actions for their bone and tendon development too.

I'd suggest that ~70-80% of training time should be moderate load/moderate volume training if muscle hypertrophy is the main objective. Depending on what other physical qualities are important to you (strength, speed, power, endurance, etc....).

You also have to make sure the sets last long enough, witness a physical slowdown and keep all your work sets within ~4 reps of absolute failure. Hence my technical failure recommendation.

If you’re not getting the result you seek after months/years of training, then a lack of stimulating reps could be one very good explanation. Take it under advisement.