How many reps should I do if I want to build muscle?

And what about if I want to just build strength?

These are the questions that have been asked for years and the reality is if you asked 10 different people, you’d likely get 10 different answers. Some would say that 10-15 reps is best for hypertrophy (muscle gain), others 12-15, but maybe it’s less than that, maybe it’s 8-10… it’s all just too confusing. Well, what If I told you I had the answer – the secret sauce to getting huge as it were? 

The reality is that the number of reps you do in a set is largely irrelevant whereas the number of sets to failure (or 2-3 before failure) is what will determine how strong and how much muscle you gain. Now before we get into it, we need to know what we mean by sets to/close to failure and why it’s important. Get ready for this because I am about to grossly over simplify the physiology of the human musculoskeletal system to you…

Our muscles are made up of hundreds to tens of thousands of individual muscle fibres (depending on the size of the muscle) and these are grouped together in bunches, and each group of muscle fibres is controlled by a motor unit and these motor units they are recruited in size – starting with the smaller ones, known as low threshold motor units and progressing to the larger ones, known as high threshold motor units. Now it’s the larger motor units that control the muscle fibres that we can make stronger and bigger, but these are only stimulated if they need to be and they only need to be for the last few reps of a set or every rep of the set when the weight is really heavy, and they will not turn on before then because the smaller motor units and their associated muscle fibres can handle it. 

So, to summarise – only the muscle fibres that are controlled by the large, high threshold motor units can increase in strength and size and they will only be recruited if we go to task failure (when you can’t do another rep) or when the weight is really heavy – around 80-85% or more of the heaviest weight you can lift. So, in essence, if you want to get stronger you can do as many reps as you like each set, provided that the set goes task you to or close to failure. 

it’s the number of sets, not the number of reps

Now that we know the sets don’t really matter too much, what is the difference for training for maximal strength and training for maximal size? The answer is in the number of sets you do, not the number of reps. One group of researchers reviewed all of the evidence on this topic they could find and their summary… “other variables such as training frequency per muscle group, training intensity, and repetition range do not alter the results provided when the total number of sets is matched” (1) It is important to know that we can definitely get a muscle stronger without making it much bigger but if we make a muscle bigger it will also get stronger. As it turns out, with as little as 3 heavy sets per week, we can have a meaningful increase in 1 rep max strength (1). With low volume training like this we can still see that even highly trained athletes can increase strength in a meaningful way. If the goal however was to increase muscle size, then we will need to complete a greater number of sets to/close to failure. There are quite a few research groups that have looked at this so there are some slight differences in the exact number of sets depending on the individual’s ability to recover, fitness, age, training history/experience etc but it comes out to be somewhere around 10 sets per muscle group per week and up to around 20 sets for those who have been training longer (2,3). 

it’s simple, but not easy.

Now of course things aren’t always as simple as they sound and there is still plenty of nuance to training for strength vs hypertrophy, but I did say I would oversimplify things slighter. Not everyone is interested in getting as large as possible and just want to get stronger and that is fine – however beyond a certain point if you want to continue to increase strength you will need to start to increase the size of the muscle as well. To do either will require a lot of consistent training, adequate sleep and nutrition and much more – but we’ll get into that another time. So, if you want to get more sets in a week try splitting up your sets per movement/muscle group over 2-3 sessions in the week (eg. 5 sets of squats, 3 times a week will mean 15 sets). To do this you’ll need to manage fatigue and soreness so give yourself more time between each set and each session. 

So, to oversimplify yet again and completely disregard all the nuance and variables that impact your training, if your goal is to get stronger without putting on much size, do fewer sets. If the goal is to increase size, do more sets. Each set will need to be taken to failure or 2-3 reps before failure.

references / to find out more

1. Androulakis-Korakakis, P., Fisher, J. P., & Steele, J. (2020). The minimum effective training dose required to increase 1RM strength in resistance-trained men: a systematic review and meta-analysis. Sports Medicine, 50(4), 751-765.
2. Ralston, G. W., Kilgore, L., Wyatt, F. B., & Baker, J. S. (2017). The effect of weekly set volume on strength gain: a meta-analysis. Sports Medicine, 47(12), 2585-2601.
3. Baz-Valle, E., Balsalobre-Fernández, C., Alix-Fages, C., & Santos-Concejero, J. (2022). A Systematic Review of the Effects of Different Resistance Training Volumes on Muscle Hypertrophy. Journal of Human Kinetics, 81(1), 199-210.