A Humble Proposal: Factoring Percentage of Reps Into Reps In Reserve Calculations
Takeaway Points:
RPE (ratings of perceived exertion) and RIR (reps in reserve) can be useful training tools for some sports where the goal is to train to failure or near failure, but there is no catch-all number that works for all exercises.
Generally, RPE is used for managing heavy efforts of weight or reps, and not for exercises where training to failure or near failure would inhibit the continuation of training like working on endurance for running a marathon.
Instead of static numbers, RPE/RIR can function as a percentage of total effort.
You can aim for something like a 50-80% range of maximum effort on an exercise and expect results. The number of sets and reps will change depending on each exercise, but the goal of effort expended remains the same.
What Is RPE/RIR?
This is probably a bit more high concept than a lot of the blog posts that I write, but here we go!
Recently, the concept of RPE (ratings of perceived exertion) has caught on in the lifting community as a way of autoregulating training - that’s to say, managing your sets, reps, or weight within a workout as a way of ensuring that the level of challenge is just right on a given day.
The original Borg RPE format was based, somewhat confusingly, on a scale of 6-20 - you perform an activity, and then give it a number between 6 and 20 to rank your effort. This doesn’t make a lot of sense and is somewhat confusing, but it makes more sense when you realize that this was intended to correspond directly to your heart rate - on the low end, 60 is a resting heart rate, and on the high end, 200 is a maximal effort. In this way, you could rank effort in a way that lined up with an objective measurement (heart rate), which made it nice and tidy to read what your RPE “should be” if you were also wearing a heart rate monitor. Naturally, this format was most useful with exercises in which effort closely corresponds to heart rate - namely, cardiovascular activities.
More recently, Mike Tuchscherer popularized the concept of RPE for powerlifting, in this case using a simpler 1-10 scale that’s a lot more intuitive. 10 represents a max effort lift, and 1 represents virtually no challenge at all.
Closely related is the concept of RIR, or reps in reserve - a 0RIR would mean that you couldn’t perform a single additional rep, a 1RIR means that you feel you could have completed one more rep if you pushed it, and so on. Often, RIR is considered to be the exact inverse of RPE - meaning, that a 10RPE is equivalent to a 0RIR, a 9RPE is equivalent to a 1RIR, and so on.
In general, studies have validated that this conception of RPE/RIR is a valuable tool which can be used to autoregulate training effectively, and to do so in a way that enhances training results. Beginners tend to have a very poor sense of their actual strength limits, and so they’re likely to misjudge their RPE’s, but more experienced lifters tend to have a better sense of things, and a little practice with RPE’s can quickly get people accustomed to using the system and thus greatly improve its accuracy. In some cases, RPE can potentially outperform more objective measures like bar speed trackers, rendering it a very useful, low-effort tool to manage training without the need for fancy equipment.
For example, you could do something like “pick a target weight, perform a number of reps that feel like a 7RPE, and then continue performing sets of that same number of reps until it now feels like a 9RPE, then stop for the day”. Conversely, you could do the same, except with a target rep range instead of a target weight. These training methods would ensure that your training is appropriately challenging for that day no matter what - it would automatically adapt to your exact strength levels on that day. Implementing some kind of autoregulation like this can often be superior to training strictly by the numbers using traditional percentages and set/rep schemes, since these methods are NOT adapted directly to your current strength levels, instead being calculated off of some previous strength baseline.
Studies have also shown that, when training to near failure, any given set of an exercise has roughly the same effect on building muscle mass, no matter what the weight. Likewise, it’s been shown that training to absolute failure isn’t necessary to maximize growth, and that similar effects can be gained by training a few reps away from failure - worse, training to absolute failure can potentially be a net negative, since it provokes a disproportionate amount of fatigue with little noticeable benefit.
Using RPE/RIR To Manage Training
In this context, RPE/RIR is a valuable tool for training near failure without having to go all the way to failure. A common prescription is to train at around 8RPE/2RIR, as this is somewhere around the sweet spot between “playing it safe” and “being near enough to failure that you’re definitely getting good results”.
However, it’s generally well understood that we can’t just use blanket recommendations for RIR/RPE.
Some exercises, for example, are simply less tolerant of training towards failure than others. It may be fine to train to absolute failure, 0RIR on lighter accessory exercises like arm work, and yet be able to bounce back and hit another 0RIR set without a ton of recovery. Conversely, a 0RIR deadlift will be completely exhausting and take a ton out of you. This could take quite a while to recover from, and still impact your performance significantly on subsequent sets. Thus, you typically have to be more careful and train at a lower RPE/higher RIR with more exhausting kinds of work.
There’s also the fact that different intensities (weight on the bar) will react to different RPE’s differently. For example, a 2RPE means a very different thing if you’re training with a weight that you could only lift for a total of 3 reps (2RPE would mean 1/3 reps per set) versus a weight that you could lift for 20 reps (2RPE would mean 18/20 reps per set). Since RPE is an objective number, which doesn’t change relative to the total number of reps you could perform, there’s the risk of making very suboptimal choices if your blanket guideline is “stick to 2RPE no matter what”.
This is also a concern because we don’t really have the full picture when it comes to the research. Exactly how far of an RIR can you train from failure and still see optimal results? We don’t know - certainly, we’re probably going to see suboptimal results if we pick up a weight we can lift for 20 reps and only perform 2, but what about 5? 10? 12? 15? - we don’t know exactly where the line is, and that’s part of the problem with making blanket RPE recommendations.
There’s also the fact that high rep sets are generally more fatiguing than lower rep sets - a known effect which explains why 20+ rep sets always feel incredibly exhausting. One study showed, for example, that even with a 2RIR, an 11 rep set at a challenging weight provoked more fatigue than a 0RIR 5 rep set.
My Proposal: Factoring in % Reps
As such, it’s clear that training to some standard RPE is NOT an all-encompassing solution for managing fatigue and challenge.
In general, I would say that using RPE in its traditional format is fine, if you’re working at sufficiently high intensities. 75% of your 1RM typically corresponds to about your 10RM, though you may be able to perform fewer or more reps than 10 at 75%, simply because every person is different and has slightly different strength/endurance curves. Anything at a 10RM and above, you can probably use Tuchscherer’s RPE without issue - training to a 1-3 RIR will ensure that you’re striking the right balance between fatigue and effectiveness, and will enable you to autoregulate your training from day to day.
But what about anything above a 10RM? Here’s where my recommendation comes in - at this point, it makes more sense to adjust your RPE/RIR values as a percentage of total reps instead of simply by training a set distance from failure.
This is based in part on two different bodies of knowledge - first, the way that endurance athletes actually train, and second, on the way that I’ve learned to train over the past year through my own experiences of shifting to a more gymnastics/calisthenics home workout format.
Runners
Endurance focused training for endurance athletes is not done the same way as training for strength and hypertrophy athletes. If it was, you could imagine that an endurance runner would run marathons regularly, building up in speed and intensity over the course of their training phase, in order to more specifically adapt to the exact distance of the marathon. In this way, they would get more and more used to that stimulus, and adapt further and further to be prepared for running the marathon.
Actual training for long distance runners, however, doesn’t really look much like that. In training, runners would rarely actually train for that long - instead, they would generally train at much lower intensities and durations - an hour here, two hours there - with a focus on increasing their total weekly work time over the course of a training career. They would also sprinkle in other work - specific work for speed, weight training for injury resistance, training on specific surfaces, and so on, to get some variety.
But nowhere in the training of the endurance athlete does it make sense to actually run a marathon in preparation for training for a marathon - this would be way too fatiguing and exhausting. So instead, they train for a couple miles here, and couple miles there, just building up their general endurance - and over time, this adds up to the ability to run a marathon anyway.
In essence, runners train at what would, within the RPE/RIR system, be VERY far away from failure. This doesn’t mean, of course, that they’re not getting exhausted from the process - just that, in a normal training context, it never makes sense for them to go all out and aim for the longest possible distance they could train. This would be way too exhausting, require a lot of recovery time, and just generally not work well in the long run. Instead, they need to manage their energy from day to day with a focus on the wider training week, focusing on lower levels of work in order to be able to return each day and continue consistently training.
This is probably a further extension of the “higher rep exercises are simply more exhausting” principle I mentioned above. When you take that to its extreme, with very light movements and practically infinite numbers of reps (as is seen in going for a run), this effect probably continues.
Calisthenics/Gymnastics
Likewise, when training with calisthenics/gymnastics, this is about as far towards the endurance end of the spectrum that it’s possible to be, while still being a lifting sport - CrossFit and Kettlebell Sport are also both significantly endurance-based.
What I found when I started training with calisthenics movements, was that super high rep sets simply got very exhausting. I tried doing sets to near failure, and just one would knock me out, in addition to not seeing consistent progress. I could do 50 pushups at a time, but if I aimed for 45 reps or so, I’d burn myself out and see that number not change much from month to month.
So I switched gears and instead focused, more like a runner, on simply increasing the total number of reps I performed on a weekly basis. I started off with about 50 reps per week split over a few workouts, then increased that number by 5% per week for a year. Any time I found that any single set of pushups was starting to get exhausting (usually at around 30+ reps) I simply added a set and split the same number of reps up over more sets, reducing the number of reps per set. By the end of the first year, I was doing 200 reps per day, split up into 5-6 sets.
In the meantime, my rep tests ballooned. I got to the point where I could do 60, 80, 100 reps in a single max effort set - despite the fact that I was rarely training above 30-40 reps per set in my actual training. By definition, I was training at a lower RPE/higher RIR the more my endurance improved - and yet, my endurance continued to improve the more I trained.
This, to me, solidifies the reality that, when training with higher endurance activities, it’s actually necessary and good to train at a lower RPE/higher RIR, and that this means we should consider some kind of reformulation of RPE/RIR when working with higher endurance work.
% Reps
One thing that struck me, in considering the problem, is that while an 8RPE/2RIR is very intuitive, it can result in a very wildly different percentage of total work depending on the rep range used.
For example, if performing an 8RPE/2RIR set with a weight that corresponds to your 3RM (in short, doing a single rep per set of a weight you could hit for 3), this corresponds to 1/3 of a maximum effort - or 33% of the potential effort you could have performed on that set.
In contrast, an 8RPE/2RIR set on a 10RM would equate to 8 reps - or 8/10 of maximum effort, and 80% of the potential effort you could have performed on that set. A huge difference - and likely to be more exhausting - that isn’t really at all counted for by the use of RPE.
Likewise, this effect gets even more pronounced, of course, when you start working at even higher rep ranges. An 8RPE/2RIR on a 20 rep set means 18/20 reps or 90% of potential effort. An 8RPE/2RIR on a 30 rep set means 28/30 reps or 93% potential effort. One could imagine a 100 rep set with 2RIR equating to a 98% potential effort.
The simple answer here would be to manage RPE/RIR to function as a percentage of total effort in this way. You can probably train somewhere in that 30-80% range of a max effort and still see results - so long, I would recommend, as each set feels appropriately challenging and exhausting. Realistically, I would say that it’s likely that you need to put in more like a 50-80% effort on most work (especially anything at a 10RM weight or more), but that something like a 30-60% range is probably fine when working on higher endurance sets at an 11RM weight or higher.
In this way, a 100RM (like my pushup max these days) might be best trained by working with sets of 30-60 reps per set, for example - far away from the traditional conception of RPE, but consistent with my findings about how endurance work should optimally be trained.
This is certainly not a suggestion that will be applicable to everyone. In large part the reason why RPE has not been investigated this way (to the best of my knowledge) is simply that this is NOT a common use case for it. Since RPE is primarily used for managing very heavy efforts, it doesn’t run into the problem of needing to account for endurance efforts. However, I think that this could be a missing piece of the puzzle in understanding why endurance athletes train the way that they do, and that this could be an interesting future study to conduct to further complete the picture.
Maybe it will turn out that future studies invalidate this concept - and maybe they will justify it. I’m excited to see future developments down the line.
About Adam Fisher
Adam is an experienced fitness coach and blogger who's been blogging and coaching since 2012, and lifting since 2006. He's written for numerous major health publications, including Personal Trainer Development Center, T-Nation, Bodybuilding.com, Fitocracy, and Juggernaut Training Systems.
During that time he has coached hundreds of individuals of all levels of fitness, including competitive powerlifters and older exercisers regaining the strength to walk up a flight of stairs. His own training revolves around bodybuilding and powerlifting, in which he’s competed.
Adam writes about fitness, health, science, philosophy, personal finance, self-improvement, productivity, the good life, and everything else that interests him. When he's not writing or lifting, he's usually hanging out with his cats or feeding his video game addiction.
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