Most training advice points in one direction: push harder, go heavier, train to failure. And there is a time and place for that approach. But consistently training to absolute failure is not the most efficient path to progress for most people, and the research increasingly supports a more measured alternative.
Reps in reserve, or RIR, is a training method built around intentionally stopping a set before failure, leaving a calculated number of reps still available.
Used correctly, it reduces fatigue accumulation, supports better volume over the course of a training block, and produces muscle growth comparable to failure training, with considerably less wear on the body.
This guide covers everything you need to know about reps in reserve, including how to calculate and implement it, what the research says, and whether it suits your training goals.
Quick Summary
- Reps in reserve is about stopping a set with a specific number of reps still available, rather than training to absolute failure.
- Recent research shows that training with 1 to 2 RIR produces similar muscle hypertrophy to failure training, while generating significantly less neuromuscular fatigue.
- The optimal RIR strategy differs depending on your goal: it has a negligible effect on strength gains but a meaningful influence on hypertrophy.
What is “Reps in Reserve” (RIR)?
Traditionally, training to failure has been considered the gold standard for maximising muscle growth. The idea is straightforward: push every set to the point where no more reps can be completed with good form.
Reps in reserve flips this slightly. Instead of pushing to complete failure, you stop your set with a specific number of reps still available. If you are doing a set of squats and you stop at 8 reps because you believe you could do 2 more before losing form, those 2 are your reps in reserve.
The number is not arbitrary. Stopping at a planned 2 RIR, for example, means you are still working hard and close to failure, but not exhausting the muscle to its absolute limit on every set.
Understanding Your Own Reps in Reserve
If you are new to training, it takes time to accurately gauge how many reps you have left. As a general guide, when your reps start to slow noticeably and bar speed drops, you are likely approaching your final few reps before failure. RIR accuracy tends to improve with experience, particularly when working in the 1 to 3 RIR range.
The Science Behind RIR: More than Just Leftovers
The case for RIR is increasingly well supported by research.
A 2024 study published in the Journal of Sports Science examined eight weeks of resistance training in trained individuals, comparing training to momentary failure against training with 1 to 2 RIR. Quadriceps hypertrophy was similar between the two groups, while the RIR group accumulated significantly less neuromuscular fatigue across the intervention.
The researchers concluded that close proximity to failure, rather than reaching failure itself, appears to be the key driver of muscle hypertrophy.
A separate 2024 meta-regression published in Sports Medicine, analysing data across multiple studies, found an important distinction worth noting: RIR has a negligible relationship with strength gains, but does meaningfully influence hypertrophy, with muscle growth increasing as sets are terminated closer to failure. This suggests that the optimal RIR strategy is not the same for strength-focused and hypertrophy-focused training.
The practical implication is that stopping 1 to 2 reps short of failure on most sets captures the majority of the muscle-building stimulus while preserving enough capacity to maintain quality across subsequent sets and sessions. This is particularly valuable over the course of a longer training block, where accumulated fatigue from failure training tends to compromise volume and performance over time.
Load Prescription
This research paper from Lovegrove et al, 2022, suggests that RIR can be a reliable tool for load prescription.
How to Calculate and Implement RIR in Your Workouts
So, you’re pumped about using RIR, but how the heck do you figure out those elusive reps left in the tank?
Step 1: Know Your Limits
You do not need to test your one-rep maximum to use RIR effectively, but having a rough sense of your capability for each exercise helps. If you have previously worked out a 10-rep maximum for a given exercise, this gives you a useful reference point.
Step 2: Listen to Your Body
During each set, check in with how many more reps you could complete with good form. If you are doing bicep curls and feel you could manage two more reps before form breaks down, your current RIR is 2. Stop there.
If your form has already deteriorated and bar speed has collapsed, you have already passed your target RIR and likely reached failure.
Step 3: Keep the Ego at the Door
RIR requires honest self-assessment. The goal is not to prove how much you can endure in a single session. It is about accumulating productive training volume across the week and across the programme. Stopping a set with 2 reps in reserve can feel unnecessary in the moment, but it directly supports better performance in the sets and sessions that follow.
Creating a Customized Fitness Plan
For some, RIR is a great approach for strength training… for others, training to failure might be better. Our guide on creating a customized workout plan helps you understand how to create a fitness plan that works for you.
Reps in Reserve Chart and Example
| Set Number | Weight Used | Total Reps Performed | RIR | Perceived Effort |
|---|---|---|---|---|
| 1 | 100 lbs | 8 | 3 | Moderate |
| 2 | 105 lbs | 7 | 2 | Challenging |
| 3 | 105 lbs | 6 | 1 | Very Hard |
| 4 | 105 lbs | 5 | 0 | Maximum |
Step-by-Step Example using the Chart
Imagine you’re doing squats with the goal of performing sets with varying levels of RIR:
- Set 1: You start with 100 lbs and perform 8 reps. After the 8th rep, you feel like you could’ve done 3 more reps before hitting failure, hence an RIR of 3. The effort felt “moderate” to you.
- Set 2: You slightly increase the weight to 105 lbs. This time, after 7 reps, you believe you could’ve done 2 more reps at most, hence an RIR of 2. The added weight and reduced RIR make the set feel “challenging.”
- Set 3: You stick with 105 lbs. This set, you manage 6 reps. You think you could’ve squeezed out just one more rep, which gives you an RIR of 1. This set feels “very hard.”
- Set 4: Keeping the weight at 105 lbs again, you push yourself and end up performing 5 reps. At the end of this set, you feel you’ve reached your limit and couldn’t have done another rep, resulting in an RIR of 0. This set is your “maximum” effort.
This progression illustrates how RIR can be used to structure effort across a session, building toward failure on the final set while preserving capacity across the earlier ones.
RIR and Strength Training Goals
| Training Goal | Suggested Rep Range | Typical RIR Range | Why This RIR? |
|---|---|---|---|
| Muscular Endurance | 12-20 | 1-2 | Longer sets challenge endurance without complete failure. Reserve is needed for multiple sets. |
| Absolute Strength | 1-5 | 1-2 | Heavy loads require recovery between sets. Failure with maximal loads increases injury risk. |
| Building Muscle (Hypertrophy) | 6-12 | 2-4 | Research supports training close to failure for hypertrophy. 1 to 2 RIR captures most of the stimulus with less fatigue than failure. |
| Improving Power | 2-6 | 2-3 | Power requires explosive effort. Higher fatigue compromises the quality of each rep. |
| Burning Calories | 10-15 | 2-3 | Sustained moderate intensity maximises calorie burn across the session without extreme fatigue. |
Muscular Endurance: Here, the aim is to condition muscles to perform over extended periods. Athletes typically stop just short of failure, preserving some energy for the multiple sets required for this kind of training.
Absolute Strength: The emphasis is on lifting heavy weights. Pushing too close to failure with maximal loads can risk injury and hinder recovery, so a small RIR is maintained.
Building Muscle (Hypertrophy): This range is the sweet spot for muscle growth. The goal is to push the muscle, creating enough stress to induce growth, but not so much that recovery is overly hampered.
Improving Power: Power is about explosive, high-intensity movements. As such, you don’t want to be too fatigued, ensuring each rep is performed with maximum explosiveness.
Burning Calories: This range is a bit of a hybrid, mixing elements of endurance and hypertrophy. The objective is to sustain longer, moderately challenging sets to optimize calorie burn.
One important distinction from the research: RIR appears to have a negligible impact on strength gains specifically. For those whose primary goal is maximal strength, proximity to failure matters less than for those focused on muscle growth. For hypertrophy, training closer to failure produces better results, making 1 to 2 RIR the recommended range rather than 3 to 4.
Benefits of Using Reps in Reserve: Not Just Playing it Safe
Avoid Burnout and Overtraining
Training to failure every session is not sustainable over a long training block. RIR allows consistent effort across weeks and months without the fatigue accumulation that eventually forces performance to drop or sessions to be skipped.
Consistency over intensity is the principle that produces the best long-term results.
If you’re following a 12 week training plan (such as this 12 week dummbell training plan), for example, this ability to pace yourself is really important.
Supports Muscle Growth
The 2024 Journal of Sports Science research found similar quadriceps hypertrophy between failure and 1 to 2 RIR training over eight weeks.
For most training contexts, stopping just short of failure captures the muscle-building stimulus without the recovery cost of going all the way to failure on every set.
Reduces Risk of Injury
Reaching absolute failure repeatedly, particularly on technically demanding compound movements like squats and deadlifts, increases the likelihood of form breakdown. RIR creates a built-in safety margin by stopping before the point where technique is most likely to deteriorate.
Improved Long-Term Progress
Every training session is a deposit toward long-term adaptation. RIR ensures those deposits are consistent. A well-managed 12 or 16-week training block with controlled proximity to failure will typically produce better results than an aggressive approach that leads to forced deload weeks or injury.
Common Mistakes and How to Avoid Them
Miscalculating Your True Reserve
Beginners often underestimate or overestimate how many reps they actually have left. If you consistently finish sets feeling like you could have done 5 more, you are probably leaving too much on the table. Periodically testing your actual limit on a given exercise helps recalibrate your sense of where failure is.
Being Overly Cautious
Leaving 4 or 5 reps in reserve on most sets is too conservative to drive meaningful progress. RIR works when you are genuinely close to failure, not simply stopping because a set feels moderately hard. The 2024 meta-regression found that hypertrophy increases as sets are terminated closer to failure, so staying too far from failure limits results.
Forgetting Form
Regardless of RIR, form comes first. Reaching 1 RIR with deteriorating technique does not count as a well-executed set. Keep technique as the primary check throughout.
Not Tracking Your Workouts
RIR is most useful when you have a record of previous sets to compare against. Logging the weight used, reps performed and RIR for each set allows you to make better decisions about progression in the following session.
There are all sorts of weightlifting apps and workout loggers you can use, but when it comes to tracking RIR, we think Alpha Progression wins hands-down. It allows you to track this training metric so you can monitor it in each workout. Check out our Alpha Progression review for a full breakdown and a unique discount code.
FAQs on Reps in Reserve (RIR)
How does RIR differ from Rate of Perceived Exertion (RPE)?
Both tools gauge workout intensity but approach it differently. RIR is a specific count of how many reps you have left before failure. RPE is a broader scale, typically 1 to 10, that rates overall difficulty. An RPE of 8 roughly corresponds to 2 RIR, but RPE can be applied to any physical activity, not just resistance training. RIR is more precise and more directly applicable to lifting.
Can beginners use the RIR method?
Yes, and it is often particularly beneficial for beginners. It provides a structured way to understand your limits and avoids the risk of overexertion early in a training programme. The main caveat is that RIR accuracy takes time to develop. Beginners tend to underestimate how many reps they have remaining, which improves with experience.
How often should I reevaluate my RIR as I progress?
Regularly. As strength improves, the weights and rep ranges that once felt like 2 RIR will feel easier. It is worth reassessing every few weeks or whenever you notice a consistent change in performance to ensure you are still working at the intended proximity to failure.
Bottom Line
The research on reps in reserve has strengthened considerably in recent years. Training with 1 to 2 RIR produces similar muscle hypertrophy to failure training while generating less fatigue, supporting better volume accumulation across a training block.
It is not about taking the easy route. Working close to failure is still hard work. RIR simply ensures that hard work is consistent and sustainable across weeks and months, rather than producing short bursts of intensity followed by forced recovery periods.
For most people following a structured training programme, targeting 1 to 3 RIR on the majority of sets, with occasional failure sets as a test, is a practical and well-supported approach to building muscle and strength over the long term.
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