How Many Reps Should You Do to Build Muscle? The Shocking Truth

Written by Jason Ferruggia Topics: Training

how many reps should you do to build muscle
If you’re a genetically average, drug-free guy who wants to build muscle fast it’s essential you know how many reps to do. Most of you are probably sabotaging your gains by training improperly.

If you’re skinnier and weaker than you liked to be you have to force your body to grow by providing a massive amount of overload. What do you think is going to do that more effectively?

Doing heavy weights for a set of 5-8 reps?

Or doing light weights for a set of 15-20 reps?

Obviously, the heavy set will provide more overload.

I could end this post here by telling you to train heavy, because that’s really the gist of it. But lets get into a little more details on exactly why that is.

The first thing you need to know is that each body part is different. That means it’s compromised of varying degrees of fast and slow twitch muscle fibers.

Fast twitch fibers are for high performance and respond best to low reps, lower overall training volume, more rest between sets and lower overall training frequency. These muscles have the greatest potential for growth.

Slow twitch fibers are more for endurance and respond better to higher reps, slightly more volume, less rest between sets and a bit more frequency. These muscles have less potential for growth.

If you were to train one fiber type exclusively it would be the fast twitch fibers.

I like to 80/20 everything in life and training is no different. You will get 80% of your growth from training the fast twitch fibers. Training slow twitch fibers (and using the methods best used to target them like high reps and low rest periods) will only result in 20% of your muscle gains.

The big takeaway is that, regardless of the body part you are training you should focus most of your efforts on low rep training. Natural lifters will get far better gains by doing most of their sets in the 5-8 rep range than they will from typical high volume approaches.

Training with low reps will increase myofibrillar hypertrophy. This is actual real growth of the muscle fibers.

Training with high reps is said to increase sarcoplasmic hypertrophy. This is an increase in the fluid volume stored in the muscles, consisting of non-contractile tissue.

It’s easy to increase the size of a muscle through sarcoplasmic hypertrophy but there are limits to it. You only get a small amount of actual size increases and it goes away rather quickly. Muscle built through low rep and heavy weight training always maintains the same dense look.

Sarcoplasmic hypertrophy induced through lighter, high rep training methods tends to disappear as soon as you lower your training volume or your carbs/fluid intake. And if you take a week or two off of training it can look like you lost ten pounds.

That doesn’t happen with low rep, heavy training, which is why it has to be the cornerstone of your training program.

Why Lower Rep Training is Actually Safer

Lower reps come with a lower injury risk when training the big lifts. I don’t believe in doing any of the traditional powerlifting or Olympic lifting exercises for more than 6-8 reps unless you have really solid technique and at least a year of experience.

When you go higher than that on the big lifts the injury risk increases exponentially with each rep as form starts to deteriorate. That’s because your smaller, stabilizer muscles will give out before your big prime movers.

When you squat for high reps your lower back will crap out from fatigue long before your legs do.

Remember that one of the keys to developing strength, while remaining injury free, is the ability to maximize tension. You can only maximize tension for about six reps, maybe eight, tops.

It’s easy to get tight, breathe properly and really dial in your form for a handful of reps. But when you start adding fatigue and labored breathing into the equation your form deteriorates. When that happens you form breaks down. Then you eventually get injured.

The Fatigue and Soreness Factor

When you focus on low reps in your training you will find that you suffer from less overall systemic fatigue than you do when training with traditional high rep, bodybuilding style workouts. This is huge if you are an athlete, a weekend warrior, or someone who just wants to feel great all the time.

When I stick to low rep training I feel like I’m floating down the street when I walk. When I start doing too much high rep pump work I feel like Frankenstein just trudging along the sidewalk.

There’s also the soreness factor to consider. The higher reps sets always produce more soreness even if the total reps are the same.

This means that doing five sets of six (30 total reps) will produce less soreness than three sets of ten (30 total reps). I don’t know about you but I hate being sore all the time. I love being fresh and ready for anything that life throws at me.

When you do high rep bodybuilding style training you can’t just jump into a pickup game at the park or beach because you’re usually suffering from residual fatigue or are just too damn sore.

A Guide to Slow and Fast Twitch Fibers

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Some muscles are predominantly fast twitch, some are predominantly slow twitch, and others are mixed.

Let’s start from the top down. But before get into let me just state that again that newbies should always stick with low rep training, no matter what. Higher reps should only be considered after you have trained properly for at least two years. And even at that point, they should only make up about 20-30% of your overall training volume.

Neck
Many people assume that since it’s a postural muscle the neck would be predominantly slow twitch, but it’s been shown that the sternocleidomastoid is actually closer to 65% fast twitch. However, due to safety issues you should train the neck with higher reps.

Traps
These are postural muscles and thus, slow twitch dominant. But that doesn’t mean you should do a dozen sets of high rep shrugs at every workout. You see plenty of powerlifters and Olympic lifter who have huge traps from deadlifts, cleans and snatches, which are all done with low reps.

The real benefit of this information is in knowing how to keep your shoulders healthy. You should do things like face pulls and incline shrugs for sets of 8-12 reps to help avoid a shoulder injury. Just don’t ever make high rep training the main focus of your training.

Shoulders
The shoulders are an interesting muscle group in that you should train them with both low and high reps. Pressing is all about performance and should be done for low reps. Then, to maximize the size of your side and rear delts you’ll want to add in some higher rep sets. This only applies to people who have trained properly for at least two years. Newbies should always stick with low rep training.

Chest
The chest is predominantly fast twitch and responds best to low reps and heavy weight. I generally recommend sets of 5-8 reps, but if you do enough volume, you can good results by doing sets of 4 and even 3 reps for chest work. I’d be very careful and limit the work you do in the lower end of the rep range, however, as it can be very hard on your joints.

On the other hand, if you do too much high rep pressing not only will your muscle growth suffer but you may notice an increase in shoulder pain from your chest getting too tight.

Lats
The lats are generally of mixed composition and thus respond best to medium reps. You can’t go wrong sticking with an average of 6-8 reps per set on lat work.

Lower Back
This is a postural muscle so it is predominantly slow twitch. If you train the lower back with movements like back extensions and reverse hypers they should be done for high reps. If you only train the lower back with deadlift  and Olympic lift variations you’ll want to stick with low reps.

Glutes
Generally slow twitch muscles that respond better to slightly higher reps. But again, you can build great glutes with squats, lunges, deadlifts and glute ham raises, all of which should be done for low reps.

Hamstrings
They are performance muscles responsible for speed and power. That means they are fast twitch and are to be trained with low reps.

Quads
The quads are comprised of a nearly equal mix of fibers. That’s why Olympic lifters and power lifters get huge quads from doing sets of 1-3 reps and why speed skaters and cyclists get huge quads from the long time under tension their sport demands.

Twenty rep squat programs became popular for a reason- because they work.

All that being said I still recommend sticking with predominantly low rep strength training for quads. One reason being that it works better for steroid-free, average lifters. The second reason being that you will already be getting “high rep” leg training in at least 1-2 times per week with your HIIT (high intensity interval training) workouts that consist of bike or sled sprints. No need for more than that.

Putting it All Together

how many reps build muscle

The main takeaway is that you should focus 80% of your training on working in the range of 5-8 reps with compound movements. That’s how you build muscle most effectively.

Do nothing but low reps during your first two years of training.

After that sprinkle in some higher reps on:

  • Neck exercises like loaded flexion and extension (10-20 reps)
  • Rear delt fly variations (10-15 reps)
  • Lateral raise variations (10-15 reps)
  • Face pulls (8-12 reps)
  • Triceps extensions and pushdowns (8-12 reps)
  • Back raises and reverse hypers (10-20 reps)
  • Glute bridges and hip thrusts (8-12 reps)

What About if I’m Over 40?
If you’re over 40 and have been training for many years you might want to stick with an average of 8-10 reps per set. And when you are strong and advanced you can actually get great results by sprinkling in a few more sets of 15-20 reps. Heavy weights for high reps can be very effective. But the key is being able to use enough load and to be able maintain proper form throughout the set. But that’s a whole other article in itself.

As long as you feel good and don’t have any serious injuries I’d still recommend training as heavy as you safely can.

What About if I’m a Female?
Because females generally tend to have more slow twitch fibers, I usually recommend that they bump the reps up slightly. There is still a time and place for sets of 5-7 reps, but in general, 8-10 reps should play a bigger roll in your training program.

And that’s a wrap, my friends.

Train hard, train heavy, train smart.