Understanding Sets, Reps, and Intensity
Rep ranges are the next biggest thing people trip over when organizing their workouts, even though they’re probably not as important as most people think. Why do we train with certain rep ranges and not others?
You may have heard that volume is the most important driver of improvement. We define volume as sets times reps times weight used. As long as volume is consistently improving, so are we. So if that’s the case, all that matters is that volume is going up, right?
Well, not quite. If we look just at volume, we immediately encounter another problem - intensity.
Intensity is a measurement of how hard a set is. However, more specifically, we use two exact definitions: relative and absolute intensity.
Absolute intensity is the exact weight we’re lifting. That might be 135lbs on a barbell, or a pair of 20lb dumbbells, or our bodyweight, or a cable machine or resistance band.
Relative intensity is the weight we’re lifting relative to our personal limits. If we imagine a graph of all the weights we can lift as well as how many times we can lift that weight, we can imagine that on one end we’d have a super heavy weight that we can only lift once, and a super light weight that we can lift a near infinite number of times.
Going for a run is an example of a super light weight (our body weight) that we can lift a near infinite number of times (each time our foot hits the pavement).
On the other end of things, imagine a very heavy bench press. There’s so much weight on the bar that we can barely lift it, and we know that if we had to add more weight or try for a second rep, we’d fail. This is called the single repetition maximum, or 1RM.
Since 1RM represents the absolute limit of our strength, we define relative intensity as a percentage of this number. As relative intensity decreases the number of reps we can perform increases, and vice versa.
Luckily, there’s also a relatively stable relationship between intensity and the number of repetitions we can complete. This means that if we say that we can lift a certain weight for a certain number of reps, we can generally predict our 1RM based off of that weight and number, and also that if we know our 1RM we can generally predict how many reps we can perform at any given weight. We can use 1RM calculators to plug in our numbers and get a rough picture of our overall strength.
That’s not to say that the predictions you get will be 100% perfect. Endurance trained lifters, lighter lifters, and women will generally be able to perform a greater number of reps at any relative intensity but “choke” faster as they approach their 1RM. In reverse, heavier, male, and strength trained lifters may be able to perform fewer reps at any relative intensity but have a higher 1RM than these reps should suggest.
Now that we understand relative and absolute intensity, let’s return to the question of volume. If the point of improvement is simply to increase volume (while applying specificity) in a handful of major lifts, where does intensity fit in?
A clear problem with using a 1RM calculator is that you cannot predict a 1RM accurately with a weight that you can lift for more than 10 reps. Why is this? Because it’s very hard for you to predict performance in a very different intensity.
It would take a long time to explain how exactly this works, but it has to do with the principle of specificity that we’ve examined above: gains in strength are not just specific to movements trained, but also to the specific intensity of the training.
Think of it like this: running at a slow speed makes you better at running at a slow speed, but not necessarily at running at a fast speed, even though you're practicing the exact same activity. In reverse, running at a fast speed makes you better at running at a fast speed, but not necessarily at running at a slow speed.
Likewise, training to improve your strength in the 1RM in the bench press won’t necessarily carry over to improving your ability to perform a set of 12 reps with a lighter weight. This means that another part of specificity is about working within rep ranges that are productive to our goals - if we're not working at the right intensity, this volume is to a certain extent "wasted". This isn't because it will have no effect, but just because we'd be getting an effect we don't really want and that isn't really optimal for training for our goals.
Because different intensities have some carryover to training with each other, but aren’t specific on their own, it’s hard to predict improvement in very different intensities. Your weight in the 1RM isn’t very predictive of your performance at 50% of 1RM, and even less when closer to 0% of your 1RM.
For this reason, comparing volume across workouts becomes hard if you’re using very different intensities. Let’s give an example of this at work.
Say you’re training with 5 sets of 5 reps at about 80-85% of your 1RM squat. Let’s also say your 1RM squat is about 200lbs, so you’re working at about 160-170lbs. If we calculate volume we get 5*5*160-170 for a volume of between 4000lbs and 4250lbs. Now let’s take that same lifter and have them work at a very different intensity: 60%. This corresponds with about 120lbs, and you can handle about 15 reps per set at this intensity. If you’re still doing 5 sets, this now comes out to 5*15*120 for a volume of 9000lbs.
Doing this calculation, you might immediately think that working at 60% is always better - you’re doing over twice as much overall volume with roughly the same amount of time spent in the gym. But this simply isn't true, because you're comparing apples to oranges. You can only really compare volume within similar rep ranges effectively.
So for example, if you went from doing 5*5 at 160lbs, and improved to doing 5*5 at 180lbs, your volume in that rep range has clearly improved. Likewise, if you go from 5*5 at 160lbs to 5*6 at 160lbs, you've also improved. But you cannot compare this progress to 5*15 at 120lbs, which is simply too different of a rep range.
The traditional way of looking at training intensity is that we have three clear zones: a strength, size, and endurance zone. The strength zone is anything between 75% and 100%, the size zone is anything between 50% and 75% (or 60-75% depending on who you ask), and the endurance zone is anything below that.
Since the relationship between intensity and reps we can complete is pretty predictable, this means that we train with about 1-8 reps when training for strength, about 8-15 or 8-20 reps when training for size, and anything more than that when training for endurance. This makes sense due to the specificity of intensity - if the intent is to improve our performance at 100% intensity, we generally want to train as close to that 100% intensity as we can consistently manage. Likewise, when training for endurance we clearly want to train with more reps and less weight.
It was generally believed that size growth occurred almost exclusively within the specific 60-75% intensity range. However, research since has shown that it’s possible to grow when working within nearly all rep ranges so long as sets are taken to near failure, meaning that it’s appropriately challenging and you can’t do too many more reps.
That being said, the traditional size growth range tends to be the range that most people work in simply because it’s the most convenient. Much higher intensity than this will be exceptionally tiring to perform and may require longer rest periods, and much lower intensity than this will soon require so many reps to get near failure that you’re just going to spend a lot of extra time working out. So while you can grow from working in other rep ranges than the traditional ones, working within the traditional size rep ranges seems to be optimal.
So long as training to near failure is done, it doesn’t really matter what rep range you work in, you’re going to grow. That means that we can almost skip the weight and rep parts of counting volume and just count sets instead. This makes it easier for us to compare volumes in significantly different rep ranges, but it’s also a bit of an oversimplification.
When working within the same rep range for the same number of sets, but increasing reps or weight, we’re seeing progress without increasing the number of sets in our training. But when comparing very different rep ranges, it’s better to count the number of appropriately challenging sets performed within that rep range instead.
So - exact volume calculations are better when comparing progress in the short term and within the same rep ranges, but counting our overall number of sets is better when comparing progress in the long term or when comparing across different intensities.
In general, the guidelines for training are this:
Strength - About 50-75% of your total sets performed within the 75-90% intensity, with some work in the 50-75% intensity. (Training much above 90% intensity is too fatiguing to be practical on a regular basis, training below 75% builds muscle which helps build strength.)
Size - About 50-75% of your total sets performed within the 50-75% intensity, with some work heaver or lighter. (Training above helps build strength, training below helps build endurance: both will help increase the amount of volume you can complete within this rep range.)
Endurance - About 50-75% of your training performed within the 0-50% intensity (namely, with cardio) with some work heavier. (Heavier work will help improve bone density, connective tissue strength, and body composition, all of which will help endurance athletes improve long term.)
Having read this article, this probably makes sense: you’re spending the majority of your time working in the most specific rep/intensity range for your goals, with some above and/or below to make you a more well-rounded lifter. So long as sets are taken to near failure, you will reap the benefits of size growth, but a moderate intensity seems to be most convenient for most lifters. When specific performance is needed (such as in strength or endurance) then lifters should match the intensity of their training to the intensity of their goals. Most people training for general health should by default train for size, as this is a more 'balanced' goal and will improve both your strength and endurance.
Takeaway points:
Volume is the best way of tracking our improvement and measuring overload.
There’s an inverse relationship between intensity and the number of reps we can complete: as reps increase weight decreases, and as weight increases reps decrease.
Specificity applies not only to movements used but also to intensities used, so we should work within the proper intensities for our goals.
Most work for strength should occur at the 75-90% intensity, most work for size should occur at the 50-75% intensity, and most work for endurance should occur at less than 50%.
We can’t really accurately compare volume within very different intensities - so while volume calculations are useful when comparing similar intensities, we can simply count the overall number of challenging sets trained to near failure when working within a variety of intensity ranges.
Further Reading:
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