How Many Reps Should You Do to Build Muscle?

Have you every wondered if you're doing the right amount of reps? Does it even matter that much? Is the 8-12 reps the ideal rep range to build muscle?

This is one of the questions I get the most as a trainer. In this post I'll show you exactly how to think about your reps, how most rep ranges build muscles and how to organize them in your workout plan.

Table of contents

• The 3 basic rep schemes

• Motor unit recruitment and the size principle

• Compound lifts vs isolation exercises

• Rep tempo

• Nutrition

The three classic rep schemes

If you go to a the gym without a plan, having no clue what progressive overload is, this is the classic rep scheme and their benefits.

With all else being equal, doing 6 to 12 reps is the best way to grow muscle.

Before you run off to the nearest gym and lift 6 to 12 reps, let me tell you the story of the motor unit recruitment and the size principle.

Motor unit recruitment and the size principle, a key to build muscle

Your muscles are made up motor units. A motor unit consists of:

• One neuron

• All the muscle fibres activated by that neuron

Motor units can be classified in three main categories:

• Small (Type 1): 1 neuron activates a small quantity of muscle fibres, doesn't require a lot of tension to get activated. These are you typical marathon runner motor units.

• Medium (Type 2B): 1 neuron activates a medium amount of muscle fibres, requires more tension to work

• Large (Type 2A): 1 neuron activates a ton of muscle fibres and requires a lot of tension to work. These are your sprinter's motor units.

The larger motor units are the ones we want to target to build muscle.

The size principle

Henneman's size principle states that motor units are recruited from smallest to largest.

In gym talk, it means that when you start a set, you'll begin by using small motor units. As the reps progress, you'll start using the medium ones and as you get closer and closer to failure, the large ones.

This means that pushing your sets close to failure is the best way to build muscle.

Now this is where it gets fun, and my trainer senses get wild.

Technically, you can take all your sets close to failure. If you do 30 reps of lat raises, you will be close to failure.

But is that really the best way to go?

If you took heavier weights and only did 10 reps, that would essentially achieve the same thing.

So then the questions becomes which would you rather do:

• 30 reps with super light weights?

• 10 reps with heavier weights?

Most people (myself included) would opt for the second option. If I can get the same results in a third of the time, I'm going to do that.

But couldn't we push it even further and say why not do 5 reps instead of 10?

This is where technique comes into play.

If I take super heavy weights and try to to a 5 rep max on lat raises, I can guarantee my form is going to suffer. I'm going to start swinging and using momentum to get the weights up. I doubt I could even go all the way up on all the reps.

This is why different exercises respond better or worse to different rep schemes.

When to use heavy vs light weights: Compound vs isolation exercises

Quick reminder

Compound lifts use two or more joints: squats, deadlifts, lunges, bench press, shoulder presses, lat pull downs, dips, rows, pull ups

Isolation only work one joint: bicep curls, leg curls, tricep extensions, leg extensions, lat raises, calf raises

Generally speaking, compound lifts respond better to heavier weights and isolation exercises to lighter weights.

If I tell you to do 8 squats, there's a high chance you'll do them. On the other hand, if I tell you to do 25 of them, you're going to think I'm crazy, or a sadist.

If I tell you to do 25 calf raises, you may grumble about it, but you know it's feasible. If I tell you to do just 5 calf raises, you will most likely run in the same probable as above.

So quick recap if you want to build muscle all over your body:

Hit chest, back and legs with heavier weights at lower reps (1-12).

Do arms, shoulders and calfs with lighter loads at higher reps (8+)

If you are a client of mine you may now wonder "well hold up, why are you even making me do more than 15 reps sometimes?"

The answer is extremely simple: I am a sadist.

On a more serious note, when I push someone past 15 reps, it's more to work on their mental resiliency than on their muscle building.

Now let's take a look at a minor detail of muscle building: rep tempo

I love using heavier weights for my squat workouts

Rep tempo and time under tension, key or bust for hypertrophy?

Rep tempo is the speed at which you lift a weight. Time under tension is how long you are handling that weight.

There has been many research on the subject, thoroughly exploring all the various combinations: slow eccentrics with slow concentrics, slow eccentrics with fast conentrics, fast eccentrics with slow concentrics, fast eccentrics and fast concentrics and all other fun combos.

The results show very little difference once volume and intensity is equated.

This means as long as you're doing as much work, at a similar intensity, tempo doesn't really matter.

I'm not saying it's useless, and in fact I am big proponent of slower eccentrics (2-4 seconds) and fast concentrics.

This is mainly do to the fact that people can maintain better exercise technique that way.

Lastly, you can do all the perfect reps in the world, but if you're not eating right, you wont build any muscle.

Nutrition for muscle growth

I won't bother you a full blow nutrition article here, but I'll leave you with the key information.

To build muscle you must:

• Eat in a calorie surplus. Start with a 250 surplus and add another 250 if you haven't gained any weight in two weeks

• Eat a minimum of 1.6g of protein per kilogram of body weight. Under this threshold you will undermine protein synthesis.

• Focus on whole, unprocessed foods to get as many nutrient as possible. Not sure what that means? Ask yourself the PHD rule: can you pick it, hunt it or dig it? If the answer is no to all three it's been processed one way or another.

• Recover properly. If you don't sleep enough, you won't produce a good amount of growth hormone, which is necessary for muscle synthesis

If you'd like further reading on the subject, check out these articles:

• How your body builds muscle

• How much protein should you eat

• Protein recipes

Conclusion: What's the best rep range to build muscle?

Very simply put, 6-12 reps is the sweet spot to build muscle. As long as you take these sets close to failure, you will recruit your large motor units.

Exercise technique matters obviously, if you're doing crappy reps, you won't target the right muscles properly and you'll risk injuring yourself.

Different exercises respond differently to rep ranges so be mindful when doing your workout plan. If you feel like you technique suffers when you go heavier, stick to lighter weights with more reps until you can manage heavier loads better.

Don't worry too much about rep tempo. You can play around with it to have fun, but it's not going to be a deal breaker for muscle growth.

Lastly, don't eat like a degenerate.

If you need help building a workout plan with the right rep ranges for your goals, check out my Online Training Programs or join my newsletter for more training tips and tricks.