Rep ranges: Are there any magic numbers for your program?

Anyone who has done any kind of resistance training would have heard about the importance of repetitions, or reps. But what are rep ranges, and why are they important?

Rep ranges: The science of repetition numbers

Anyone who has done any kind of resistance training would have heard about the importance of repetitions, or reps. But what are they, and why are they important?
‘Reps’ simply refer to how many times you perform a movement from a start to finish position within a set during your resistance training programme. When you first start doing some kind of resistance training, there is usually a golden number that is fabled to tick all the boxes. Ten reps for strength, 10 reps for size, 10 reps to keep you from getting injured, 10 reps to overturn seven years of bad luck if you’ve just smashed a mirror … there’s nothing this magic number can’t help you to achieve!
But there must be more to it than that right? The huge people in the gym with the weightlifting belts on often only do a handful of reps, and people obviously do much more than 10 reps in a circuit class, right? So, what difference does it make when we do a different number of reps and what should we be doing with different goals in mind?
Today we’ll look into the science behind altering our rep numbers and see whether there are other variables in this puzzle that we should consider as well.

A brief history of rep ranges

When I first started studying resistance training in high school nearly 20 years ago, the basic formula was this: a rep range of 1-3 was for power training, 4-8 was for increasing strength, 8+ helped promote hypertrophy (getting bigger muscles) and 12+ promoted muscular endurance. These numbers shifted slightly depending on which textbook you were looking in, but you get the idea.

Is that the answer then? Does this age-old wisdom still hold true? And do we need to also consider other variables such as how many of these sets we do and intensity at which they are performed?

The science of sets and reps

When looking into the research, let’s start with intensity. This refers to how difficult something is. We could do 10 reps that are super easy if the weight is really light, or we could do 10 very challenging reps if the weight is near our maximum. These are obviously two very different sets of 10.

It is proposed that if you’re a beginner, then a lower intensity is fine, with fatigue coming about as a result of a rep range that’s a little higher – perhaps 12 to 15. This allows us more opportunity to practice the movement rather than throwing in the additional complexity of a very heavy load. I feel some gym goers would do well to revisit this step, but we’ll come back to terrible form and gym ego another day perhaps 🙂 

When you finish your final reps, you may be able to do three more reps perhaps. This is fine as here, we’re looking to improve the neural links between your brain and muscles. This will see improvements in strength (mainly through those neural pathway improvements) and in time an increase in muscle size.

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If you’re more experienced and looking to increase strength, then we can go back to my high school textbook and drop down to the 4-8 rep range. Here we will obviously lift more per rep than if we were lifting for 12 to 15 but we will also look to increase the intensity. Here we may only be able to do one or no additional reps when we complete the final rep of the set. For both beginners and more experienced lifters, you will increase the load over the weeks as it becomes easier.

The other variable to consider is – how many of these sets should we be doing? When we multiply our number of sets by our number of reps by the load of those reps, we get our total volume. Understanding this total volume helps us to answer this question. Beginners seem to be better off performing 3-4 sets per muscle group (see, even in the science we’re guided towards three sets of 10!). As we become more advanced we can increase our set count but likely not beyond six sets per body part. The above ranges refer to a goal of increased strength. But what if we’re keen to increase our muscle size? Well, as we’ve said, there is a good level of crossover here as often strength leads to size and vice-versa. But there are some specifics we can consider.

When it comes to increasing muscle size, it seems my high school textbook was pretty close to the science again. It looks as though 8-10 reps (there’s that number again) will aid with increased muscle size due to the increased activity of chemical pathways associated with muscle growth. Now, just to throw a curveball into the mix, it has also been shown that doing a high rep (25 to 30 reps) set immediately after a 5-sets-of-5 reps strength-based exercise led to increased muscle size and increased strength compared to just doing the 5 sets of 5 reps. The group responsible for this research was unable to explain exactly why this might be the case but recommended adding a single high rep set at the end of each exercise if you wanted both strength and size increases.

In the years since that study, our understanding has grown a little and now there is actually a reasonable amount of evidence for resistance training using higher reps and lower loads. This is in part because it ensures we recruit all of our muscle fibres when we lift. Our muscles have a mixture of type I and type II fibres, and typically the slowest, smaller type I fibres will start first before the bigger type II fibres, with greater potential to produce force, jump in to help.

Beyond fatigue, working for a longer period also ensures that we adequately stress our metabolism. This stress will trigger the release of important anabolic (which means to make bigger) hormones such as insulin like growth factor-1 (IGF-1) and human growth hormone (HGH). In fact, HGH may actually increase as levels of lactic acid increase. It should therefore be evident here why higher reps may therefore produce more HGH than lower reps (if you’re not sure, see which produces more lactic acid in your legs – a set of four squats or a set of 20!).

The key here goes back to intensity and how many reps you could do at the end of a set. If in doubt, make sure that number in reserve is low. That way you know you’ll be getting good fibre recruitment and all the benefits that brings with it.  

How many reps should I do? Tips for your programme

If you’re a relative beginner then it’s comforting to know you probably don’t need to worry about this sort of thing too much anyway. You will see increases in strength quite quickly just by teaching your body how to move something heavy. As you become more experienced, those traditional rep ranges aren’t too far away from being great guidelines. Low reps for power, medium for strength and higher reps for hypertrophy and endurance. Remember though, it’s a continuum and you’ll get improvements across the board once you’re experienced enough to keep the intensity high.

Taking all of this information together really is only the tip of the iceberg. We haven’t spoken about how fast these reps should be – if in doubt, always maintain control throughout the concentric (up) and eccentric (down) phase. And we haven’t spoken about the length of rest periods; generally if training for strength and power you can rest for longer  – two to five mins for strength and power respectively and shorter (60 to 90 secs) when looking to increase muscle size. These are lessons for another day, but you can always play around with them if you’re looking to add a bit of variety to a stagnant routine.

How many reps to build muscle? Well, it depends…

As so often is the case, the answer to the correct rep range can be a bit of an ‘it depends’. This is, in part, because our response to exercise is so individual. That’s why you might see two elite athletes swearing by quite a different rep count in their training.

The good news though to help us cut through this confusion is the crossover in rep number and the benefits they yield. It’s likely that the most important thing is to be consistent and to lift with intensity.

Beyond that, you can play around with things armed with the information above to see what works well for you. Whatever you do though, make sure those reps are done through a full range of motion. But that’s also a pet peeve for another day…

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