RIR (Reps in Reserve) — how to measure intensity

RIR (Repetitions In Reserve) is a method of measuring intensity that indicates how many more repetitions with proper technique you could have performed before reaching technical failure.

What Exactly is RIR (Repetitions in Reserve)

RIR, or "Repetitions In Reserve," is a tool for self-regulating training load. Instead of blindly following prescribed weights, RIR prompts you to listen to your body. The concept is simple: at the end of each set, you estimate how many more full repetitions you could have completed if necessary. This estimation determines the intensity of the set. For example, if you finish a set of 8 squats and feel you had enough strength for exactly 2 more before your technique broke down, you were working at RIR 2. If, after the 8th repetition, you could barely lift the bar and knew that a 9th would be impossible, you were working at RIR 0. RIR is closely related to another scale for perceived exertion – RPE (Rate of Perceived Exertion). They are two sides of the same coin. The relationship is inverse: RPE 10 (maximal effort) corresponds to RIR 0, RPE 9 to RIR 1, and so on. While RPE asks "how hard was it?", RIR asks "how much more could you do?". For many athletes, RIR is more concrete and easier to apply.

Comparison Table: RIR vs. RPE

RIR	RPE Equivalent	Sensation Description	Suitable For
RIR 0	RPE 10	Complete failure. Impossible to perform another repetition.	Max strength testing (rarely).
RIR 1	RPE 9	Very hard. Only strength for exactly one more repetition remains.	Peak strength training.
RIR 2-3	RPE 7-8	Challenging but controlled. Speed decreases.	Primary volume for hypertrophy.
RIR 4+	RPE 5-6	Moderate. Speed is high, technique is stable.	Warm-up, technique, deload.

How It Works in Practice

Using RIR changes how you select the weight for the day. Instead of trying to lift 100 kg for 5 repetitions because the program says so, you adjust the weight to achieve the desired RIR. Example for hypertrophy: Your plan says: "Leg press, 4 sets of 10 repetitions @ RIR 2". 1. First set: You choose a weight you think you can do about 12 repetitions with. Let's say it's 150 kg. You perform 10 repetitions. At the end of the set, you feel strong and know you could have done 3 more repetitions. This means you were at RIR 3, a bit lighter than the target. 2. Second set: To get closer to RIR 2, you increase the weight slightly, for example, to 155 kg. You perform 10 repetitions, and this time the feeling is exactly as it should be – hard, but with a sense of 2 repetitions left in reserve. You have successfully achieved RIR 2. 3. Third and fourth sets: As fatigue accumulates, even 155 kg might become too heavy. If, on the third set, you feel you barely managed the 10th repetition (RIR 0-1), for the fourth set, you should reduce the weight back to 150 kg to stay within the target RIR 2. This approach ensures that each set is productive without leading to unnecessary exhaustion.

When and How to Use It

The application of RIR depends entirely on your goal. For muscle hypertrophy: The main part of your training should be in the RIR 1-3 range. This is the "sweet spot" that provides a strong mechanical stimulus for growth without overloading the central nervous system (CNS). Working at RIR 2-3 allows you to accumulate a high total volume of work – a key factor for hypertrophy. Sets to failure (RIR 0) can be used sparingly, for example, on the last set of an isolation exercise. For maximal strength: Here, the focus is on heavy weights and low repetitions. Training primarily occurs in the RIR 0-2 range. Sets with RIR 1 (e.g., 3 repetitions with a weight you could do 4 with) are extremely effective for building strength without the risks associated with constant failure. RIR 0 is reserved for the final stages of preparation or for testing a new personal record (1RM). For technique and endurance: When working on the technique of a complex movement (like gymnastic elements or Olympic lifting) or for muscular endurance, it's best to stay in the RIR 3-5+ range. The goal is to accumulate many repetitions with perfect form. Technical failure here is counterproductive as it reinforces incorrect movement patterns.

Common Mistakes and Misconceptions

Despite its effectiveness, RIR is often applied incorrectly. Understanding these mistakes is key to getting the most out of the method. The first and biggest misconception is that you always have to train to failure (RIR 0) to achieve growth. Scientific data and practice show that sets stopped 1-3 repetitions from failure are just as effective for hypertrophy but generate significantly less fatigue. This allows for higher training frequency and volume in the long run. Another mistake is the inability to honestly self-assess. Many trainees, driven by ego, systematically underestimate their RIR. They finish a set to absolute failure and log it as "RIR 2." This renders the entire system meaningless and leads to overtraining.

RIR or RPE – Which is better?
Neither is "better"; they are interchangeable. RIR (how many reps are left) is often easier for beginners to understand and apply, while RPE (how hard it feels) is more abstract. Use the system that works better for you. RPE 9 = RIR 1.

How can I become more accurate in determining my RIR?
With practice and honesty. Occasionally, on a safe exercise (e.g., on a machine), do a set to true technical failure. This will give you a clear idea of what RIR 0 feels like. Filming your sets also helps you objectively see when the bar speed slows down and technique starts to deteriorate.

Should RIR be the same for all sets of an exercise?
No. Due to accumulating fatigue, it's normal for RIR to decrease if the weight and reps remain constant. A good strategy is to start with RIR 3 on the first set and finish with RIR 1 on the last, or reduce the weight to maintain a consistent RIR.

See more in the fitness guides of Sport Zona Academy.

See more in the fitness guides of Sport Zona Academy.