Last Updated: Dec 23, 2018
Everyone seems to have different thoughts on the matter of how many reps is best when you want to build muscle mass. If you ask 10 different trainers at your local gym what they think is an ideal rep range, I wouldn't be surprised if you got 10 different answers, most simply based on bro-science.
But you'll be pleasantly surprised to hear that there IS indeed an answer to this conundrum, backed by good-old science, and something you should implement in your muscle building workouts if you want an effective routine that leads to maximum muscle gains.
In this short and sweet article we'll explain what the ideal rep range for hypertrophy (read: muscle gain) is, and more importantly why this is so. The amount of reps you perform in your weight lifting sets will dictate what type of results you get from your training. Doing a low amount of reps is the most effective way to build muscle, period. Higher rep ranges won't stimulate your muscles as well for muscle growth, and are more suited to gain muscle endurance with only a little bit of muscle gain. But you want the biggest and best muscle gains possible, so low reps are the way to go. So how many reps is ideal for results?
Without beating around the proverbial bush, the best rep range to build muscle as effectively as possible is 5 - 7 reps. Why? Performing 5-7 reps per set has been proven to be the most effective range for muscle stimulation and growth. So, this means you need to use a weight that is challenging for you to reach 5, 6 or 7 repetitions. If you are able to do more than 7 reps on a particular exercise then you need to increase the weight, and on the other hand if you can't reach the 5th rep you need to lower the weight a little bit. So put simply, if you can do more or less than 5-7 reps on one of your lifts, you don't alter how many reps you do. What you change is the amount of weight you lift so that you fall back into that effective 5 to 7 range.
Why is 5-7 reps an ideal range to build muscle? There are a few solid reasons, and this isn't just my own subjective opinion but based on extensive research and I advise you to do the same and not to just blindly take my word for it.
Firstly, doing less reps in each set will allow you to use all of your energy and strength in those reps. The more reps you do then the more you will lose focus on performing them with everything you've got. Using a low rep range will cause the most muscle growth because you are training as hard as you possibly can, with the heaviest weight that you can use.
More importantly though, a lower rep range is proven to be better for muscle growth thanks to some basic human biology. There are two main types of muscle fibers in your body, slow twitch fibers and fast twitch fibers.
Slow twitch fibers are used the most during endurance type exercise, but they don't have a lot of growing capability. On the other hand, the body taps into fast twitch fibers for shorter and more intense movements. Fast twitch fibers have much more capability for gains in muscle size and strength than slow twitch fibers have.
You see where I'm getting with this? Using low reps such as 5-7 will use the most fast twitch fibers because for these reps you need a short burst of immense energy to perform them. That's what you want, the most fast twitch fibers utilized in your workouts. This is sure to cause the most muscle growth possible.
On top of all that, there's another good reason why 5-7 reps is ideal. Using this amount of reps for your sets will decrease lactic acid secretion in your muscles. Lactic acid is metabolic waste produced by the body, and the less of it you produce in your muscles the better.
Should you stick to the rule of using 5-7 reps for every single exercise you perform? No, as with most things in life, there are some exceptions. For example, the following exercises should be done with a higher rep range: abs, forearms, calves, and upper traps. How many reps is effective for these exercises?
I recommend using perhaps 8-12 reps for these particular muscle groups. This is because they're mostly made up of slow twitch fibers, so you will need to use slightly more reps to stimulate them fully. But this applies only to the muscle groups I have listed, and all your other exercises will build more muscle with 5-7 reps.
Now you understand why 5-7 reps is an ideal rep range to use for your weight training sets, so if you hear the old argument of how many reps you should use for the best muscle gains, you now know the honest and truthful answer based off aggregate experiences of many seasoned lifters and professionals in this field (not me).
In other words, you know the safest bet in terms of how many reps is best for muscle gain. Sure, you can get size gains using other rep ranges, but stick to 5-7 if you want maximum hypertrophy results from your hard work in the gym. Yes, 8 reps is fine...doing an extra rep isn't going to change much...but it's when you creep into 10+ that you're not really being as effective in your strategy as you could be.
Don't get me wrong, you can still get results and build muscle with higher reps, but it's not the most effective way to promote hypertrophy (scientifically speaking) and you'll be spinning your wheels a bit with high rep workouts (at least for building muscle, that is). Hope that helps, and stay strong.