If you’ve ever had fitness content recommended to you by a social media algorithm, you’ve most likely been shown some workout recommendations. Often times a fit influencer edits together a workout of theirs and writes up what you should do to look just like them. Almost every time, the recommendations they give involve a static number of sets and reps like “do 8 - 12 reps for 3 sets” or something similar. All of those recommendations are missing something absolutely crucial; progressive overload.
Progressive overload is the key to getting results out of your workout. Any workout plan or recommendation that does not include progressive overload will not help you do anything other than spin your wheels while staying in place. Here’s an improved version; “use a challenging weight that you can do 8 - 12 reps with and try to increase the number of reps you do every workout.”
But why 8 - 12 reps? In my post on the basics of training for hypertrophy, I wrote that anywhere between 5 and 30 reps is good. Isn’t that too big of a range? Why is it that so often gyms, trainers, and online programs suggest somewhere between 8 and 12 reps? Is there a “correct” number of reps you should be doing?
What science says
I don’t have access to scientific journal publications, so I won’t be linking the actual studies themselves, but I assure you that there is a great consensus between exercise physiologist and the folks that actually do exercises professionally that any number of reps within the range of approximately above 5 and approximately below 30 will yield the same hypertrophic stimulus, assuming the sets are taken relatively close to failure.
Assuming that your goal is hypertrophy, you will want to maximize the tension your targeted muscles experience. If you select a weight that you can do 10 reps on before failing the 11th rep and perform each rep with proper form, you will experience approximately the same muscular tension as you would if you selected a slightly lighter weight that you could do 14 reps with before failing the 15th rep. I will write about the importance of working sets close to failure in a separate post, but the point to keep in mind here is that both of the set of 10 and the set of 14 take your muscle relatively close to failure.
A heavier weight is harder for your muscle to lift and thus produces more tension on the muscle than a lighter weight. But a lighter weight can simply be lifted a few more times to get your muscle to the exact same place you did with the heavier weight - close to failure. Since we’re training for hypertrophy, we don’t care how heavy the weight is, we only care about producing good stimulus. So picking a lighter weight and doing more reps can still get you to the same place of muscular tension.
Why not 4 and 31?
There is nothing magical about 5 and 30. Doing 4 reps or doing 31 reps is not going to have a significantly different effect. The reason there’s a range is because you start running into other problems when you get to either end of the range.
If you lift really heavy weights for just a couple of reps, you’re really doing strength work instead of hypertrophy. Doing 3 reps with a really heavy weight where the last rep is your absolute last one and you would fail the 4th is still going to stimulate your muscles to grow, but it’s not going to be as efficient at stimulating them compared to doing a lighter weight for 6 reps. The heavier the weight, the harder it is to control it on the positive/concentric and negative/eccentric parts of the movement, meaning you will have a harder time targeting the muscle you want to work. Other muscles will want to help you lift the heavy weight, which minimizes the tension your target muscle experiences. I will write more in depth on these concepts in a separate post, but you should always remember that a powerlifter will use any and all muscles to get the weight up while a bodybuilder will try his hardest to use only the one muscle he wants to experience muscular tension to stimulate it to grow.
Lifting too light, on the other hand, will cause you to simply get tired faster than your muscles get tired. Lifting weights takes cardio and you don’t want heavy breathing to be the limiting factor that prevents you from pushing your muscle close to failure. The more reps you do, the more you run the risk of join pain or weak writs giving out before your target muscle. What if you lose count on rep 23 because your mind starts to wander off? You need to be picking weights that actually challenge you, that force your muscles to do unusually difficult work. Doing high reps is perfectly fine and there’s nothing necessarily wrong with 31 reps, but the higher you go, the less reasonable it is to expect a stimulus that is as efficient as one you can get from a slightly higher weight and a lower rep range.
Goldilocks zone
You often see recommended reps like 8, 10, and 12 because a) they’re really nice round numbers that can easily be remembered without losing count and b) they’re squarely within the 5 - 30 range, making it more likely that you efficiently stimulate your muscles. Working closer to 5 will allow you to not only stimulate hypertrophy, but also improve on strength since you are using a relatively heavy weight. Allowing for room between 8 and 12 will incentivize people to push themselves, to challenge their muscles, and hopefully discover that they’re stronger than they think while also getting closer to failure.
Should you be doing reps in the lower or the higher end of the rep range? That depends on your exercise. Compound exercises like deadlifts, bench presses, squats, and rows utilize multiple muscles. For example, a bench press is intended to mostly work your pectoral chest muscles, but also strongly engages your triceps. For these types of exercises, you should move down the scale to the lower end of the rep range and pick a weight you can do for 6 - 10 reps. It doesn’t mean that 14 or 16 reps is bad, you can absolutely do that, but if you want to maximize efficiency in stimulating your muscles, you should pick heavier weights for lower reps.
For isolation exercises that are intended to stimulate only one specific muscle, you should move up the scale of the rep range towards 12 - 16 reps, or even 20+. These movements are typically done with lighter weights because you want to maximize your mind-muscle connection (you want to feel the muscle contract) and doing them with a lighter weight and more reps will help with that. In addition, some isolation exercises may make you more prone to injuries (like working the deltoids of the shoulders) and picking a lighter weight while doing higher reps will minimize the chances of injury. Isolation exercises don’t have to be done after compound movements, but they often are, so you will already be tired and your muscles may have already put in some work, which means you have to lighten the load to work them again. In general, using a single muscle like the bicep on a bicep curl will not allow you to move as much weight as using both the bicep and a variety of back muscles on a row movement, so picking lighter weights and higher reps is more sensible.
There isn’t a perfect number of reps for any one exercise. The intent is always to maximally stimulate the target muscle and continue to increase that stimulus over time to achieve results. Whatever rep and weight combinations make that happen for you is what you should do, especially if you’re lifting at home and don’t have access to a wide variety of weights. Remember that as long as your sets are relatively close to failure, you can do sets of anywhere between 5 and 30 reps.