You finish a set, rack the weight and wonder: was that actually hard enough?
Maybe your program says three sets of ten, but that still leaves an important question unanswered. Were those ten reps close to your limit, or could you have done another ten?
The number of reps matters. The weight matters. But neither tells the whole story without effort.
That is where RPE and reps in reserve can help. They give you a practical way to judge how hard a set was, adjust your training to how you are performing that day and make progression more deliberate.
They are useful tools—not perfect measurements and definitely not a reason to turn every set into a maths test.
What is RPE in strength training?
RPE stands for rating of perceived exertion. In strength training, it is commonly scored from 1 to 10 and linked to how many good repetitions you believe you had left at the end of a set.
An RPE 10 means you had no more clean reps available. An RPE 9 means you probably had one. An RPE 8 means you had roughly two.
Importantly, RPE 10 does not mean you need to attempt another rep and get stuck underneath the bar. It means that, based on your judgement, another rep with acceptable technique was not there.
What are reps in reserve?
Reps in reserve, usually shortened to RIR, asks the same question more directly:
How many more good reps could I have completed before reaching failure?
The common strength-training relationship looks like this:
| RPE | Reps in reserve | What the set should feel like |
|---|---|---|
| 10 | 0 RIR | No more clean reps available |
| 9 | 1 RIR | One more good rep was probably there |
| 8 | 2 RIR | Challenging, with roughly two good reps left |
| 7 | 3 RIR | Solid work, but clearly short of your limit |
The further you get from failure, the less precise that conversion becomes. There is not much value in arguing whether a very easy set was exactly RPE 5 or RPE 6.
For most people, RIR is the easier place to start. “How many more could I have done?” is usually more useful than trying to assign an abstract effort score.
Why fixed reps are not enough
Imagine two people both complete ten goblet squats with the same weight.
The first person could have completed another ten reps. The second could barely have completed one more without losing position.
On paper, they did the same set. In reality, the training demand was completely different.
This is why a program built only around fixed sets and reps can miss important context. Your strength can move from session to session because of sleep, stress, food, fatigue, training history and plenty of other factors.
RPE or RIR allows the plan to respond without becoming random.
If your program calls for eight reps at roughly 2 RIR, you choose a load that leaves you with about two good reps at the end. On a strong day, that load may be heavier. On a rough day, it may need to come down.
The target effort stays reasonably consistent even when your performance does not.
How hard should you train?
There is no single RPE that every person should use for every exercise. Your goal, experience, exercise selection, weekly workload and ability to recover all matter.
As a practical starting point, many working sets can finish with one to three good reps in reserve. That is hard enough to create a meaningful training stimulus without demanding failure on every set.
There are times when training closer to failure makes sense. A controlled set on a leg extension or cable curl carries a different consequence from grinding a heavy squat until your technique falls apart.
There are also times when stopping further away from failure is sensible: early in a new program, during a high-volume week, while learning an exercise or when fatigue is already high.
Recent research in trained people has found that sets stopped around one or two reps short of failure can produce similar muscle growth to sets taken to momentary failure. That does not prove effort is unimportant. It shows that you do not need to empty the tank on every set to make progress.
The aim is not to train as hard as possible every day. It is to train hard enough, recover and keep progressing.
RIR is a skill, not an exact reading
Your watch cannot tell you how many reps you had left. RIR is an estimate, and estimates improve with experience.
Newer lifters often stop a set because it feels uncomfortable, not because the target muscles are genuinely close to their limit. More experienced lifters are generally better at judging how close they are to failure, although nobody is perfectly accurate.
The estimate also tends to become harder with light loads and long sets. A set of twenty leg extensions can burn badly while several physical reps remain. Breathing, discomfort and work capacity can feel like muscular failure before the muscle has actually reached it.
That does not make RIR useless. It means you should treat it as a practical guide and get better at using it over time.
To improve your judgement:
- Keep your exercise technique and range of motion consistent.
- Record the weight, reps and estimated RIR after each working set.
- Use safe exercises to occasionally learn what genuine technical failure feels like.
- Review video where useful instead of relying only on how dramatic a set felt.
- Compare your estimate with your performance across the following weeks.
You are looking for a reliable pattern, not laboratory precision.
How to use RPE when your weights are limited
The original conversation behind this article took place when many people suddenly lost access to their normal gym equipment. The situation was unusual, but the training lesson remains useful.
You can still make a light weight challenging. Research has shown that lighter-load training can support muscle growth when the sets involve sufficiently high effort. Heavier training remains more specific and generally more effective for improving maximal strength, but a light dumbbell or bodyweight exercise is not automatically useless.
If you cannot add weight, progression might come from:
- completing more good reps with the same load;
- using a larger range of motion;
- adding a pause in the hardest position;
- slowing the lowering phase;
- moving from a two-limb exercise to a single-limb variation;
- choosing a harder version of the movement; or
- adding a set when the extra volume is appropriate.
Change one main variable at a time. If you change the exercise, tempo, rest period and number of sets together, you will not know what actually improved.
A simple progression example
Suppose you only have one pair of dumbbells for rows.
Your target is three sets of 10–15 reps at approximately 2 RIR, with 90 seconds of rest. In week one you record 13, 12 and 11 reps. Over the next few weeks, you try to add clean reps while keeping the same technique, rest and target effort.
Once you can reach the top of the range across all three sets at roughly 2 RIR, make the exercise harder. Add load if you can. If you cannot, use a more challenging variation, a pause or a longer range of motion and begin building again.
That gives you something measurable to progress without pretending the only form of improvement is more weight on the bar.
Common RPE and RIR mistakes
Treating every set as RPE 10
Training to failure can be useful, but doing it constantly can create fatigue that interferes with the rest of your session or week. More suffering does not automatically mean a better program.
Stopping when the set starts to burn
Discomfort and muscular failure are not the same thing, particularly during high-rep training. This is one reason people often underestimate their RIR with lighter loads.
Allowing technique to change
If your range shortens and your body position changes as the set gets harder, your numbers stop meaning the same thing. Count good reps performed to the standard you intended.
Chasing false precision
You do not need to decide whether a set was RPE 8.2 or 8.5. Use the scale to make better decisions, not to create another thing to overthink.
Ignoring the rest of the program
One hard set does not exist in isolation. Your exercise selection, total volume, training frequency, recovery and actual goal still matter.
The program still has to fit the person
Effort targets are useful, but they cannot rescue a program you dislike, cannot complete or do not understand.
One of the strongest points from my conversation with Sam was that the coach and client both have a role. The coach needs to understand the person’s goal, experience and real-life constraints. The client needs to communicate honestly and complete the work as consistently as they can.
A theoretically perfect program is useless if it does not fit the person living it.
RPE and RIR help because they introduce flexibility without abandoning structure. You still have a plan. You are simply adjusting the day’s work to what you can genuinely produce.
The takeaway
You do not need to reach failure on every set, and you should not finish every session wondering whether you did enough.
Start by learning what one to three good reps in reserve feels like. Track your load, reps and effort. Keep your technique consistent. Then use the pattern—not one heroic workout—to guide your progression.
The goal is not perfect numbers. It is better judgement, better training and a program you can keep moving forward with.
Want the guesswork taken out of your training?
KZPT online coaching gives you a personalised program, regular reviews and a coach who can adjust the plan around your goals, performance and real life.
Research referenced
- Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve (opens in a new tab)
- Estimating Repetitions in Reserve in Four Commonly Used Resistance Exercises (opens in a new tab)
- Similar Muscle Hypertrophy Following Eight Weeks of Resistance Training to Momentary Muscular Failure or With Repetitions-in-Reserve (opens in a new tab)
- Muscle Failure Promotes Greater Muscle Hypertrophy in Low-Load but Not in High-Load Resistance Training (opens in a new tab)
- Without Fail: Muscular Adaptations in Single-Set Resistance Training Performed to Failure or With Repetitions-in-Reserve (opens in a new tab)
General educational information only. Exercise should be adjusted to your experience, health and circumstances. Seek appropriate professional advice if you have pain, an injury, a medical condition or concerns about starting or changing your training.