Reps in Reserve During High Rep Training: What You Need to Know
When you’re doing high rep sets, the question of how many reps you should leave in the tank becomes important. Reps in reserve, often called RIR, refers to how many additional repetitions you could theoretically complete before reaching complete muscular failure. Understanding this concept can help you train smarter and recover better.
The Traditional Approach to Training to Failure
For years, fitness enthusiasts believed that training to absolute failure on every set was the only way to build muscle. The logic seemed sound: if you want maximum growth, you need maximum effort. However, recent research has challenged this assumption. When researchers compared people who trained to failure versus those who stopped a few reps short, the results were surprising. The group that didn’t train to failure actually performed more total repetitions across all their sets while maintaining better recovery. This matters because total volume, not just effort on individual sets, drives muscle growth.
Why Reps in Reserve Matters for High Rep Work
High rep training typically involves sets of 15 or more repetitions. At this rep range, the dynamics of training change compared to heavy lifting. High rep sets create significant metabolic stress, which is a powerful driver of muscle growth. However, this metabolic stress also creates substantial fatigue in your nervous system and depletes your energy stores quickly.
When you’re doing high rep work, leaving reps in reserve becomes particularly valuable. If you push every single set to complete failure, you accumulate fatigue faster than your body can recover from it. This excessive fatigue can actually slow your progress because you won’t be able to train as frequently or maintain consistent performance across multiple sets.
The Recovery Advantage
One of the clearest benefits of using reps in reserve during high rep training is improved recovery. Training to failure generates higher fatigue levels, particularly in compound movements. When you stop a few reps short of failure, you reduce this fatigue accumulation while still providing enough stimulus for muscle growth. This means you can train more frequently and maintain better performance in subsequent workouts.
Think of it this way: if you completely exhaust yourself on Monday, you might not be ready for another quality session until Thursday. But if you leave reps in reserve on Monday, you might be ready to train again on Wednesday. Over the course of a month, that extra training session could make a significant difference in your results.
The Effort-to-Fatigue Ratio
Research shows that the effort you put into your sets matters more than the exact rep range. A 2024 meta-analysis found that hypertrophy results improved when sets were taken closer to failure. However, “closer to failure” doesn’t necessarily mean “to failure.” For high rep training specifically, stopping at an RPE of 8 or 9 out of 10 (meaning you have one or two reps left) provides excellent stimulus while managing fatigue.
This approach is especially important for beginners and intermediate lifters. Novice trainees should aim to finish all sets with skilled compound movements at an RPE of 8 to 9 at most. You can reserve training to complete failure for isolation movements and machines, where the injury risk is lower and recovery demands are less severe.
Practical Application in Your Training
If you’re doing high rep sets of 15 to 20 repetitions, aim to leave about one to two reps in reserve on most of your sets. This means stopping when you feel confident you could do one or two more reps if you pushed hard. On your final set of an exercise, you might push closer to failure if you want, but even this isn’t necessary for growth.
For example, if you’re doing a set of 20 dumbbell curls, you might stop at 18 reps on your first set, 17 on your second set, and 16 on your third set. You’re still accumulating significant volume and creating metabolic stress, but you’re not completely destroying your nervous system in the process.
The Diminishing Returns of Volume
It’s worth noting that volume does drive hypertrophy, but there are limits. Your first hard set of an exercise provides roughly two-thirds of the growth stimulus you’ll get from that exercise. Each subsequent set provides additional stimulus, but with diminishing returns. If you train to complete failure on every set, you might actually do fewer total sets because you’ll be too fatigued to continue. By using reps in reserve, you can often complete more sets while maintaining better form and consistency.
Balancing Effort and Sustainability
High rep training is valuable for building muscular endurance, improving work capacity, and providing a joint-friendly training stimulus. However, these benefits only materialize if you can sustain the training over weeks and months. Training to complete failure on every high rep set often leads to burnout, reduced training frequency, and ultimately slower progress.
By leaving one to two reps in reserve during high rep training, you maintain the stimulus for growth while preserving your ability to train consistently. This approach also reduces injury risk because you’re maintaining better form throughout your sets. When fatigue becomes extreme, form breaks down, and injury risk increases.
Individual Variation and Flexibility
Not every day will feel the same. Some days you’ll feel strong and energized, while other days you’ll feel flat and tired. Rather than rigidly sticking to a specific rep target, many coaches recommend providing clients with rep ranges instead. If you’re supposed to do 15 to 20 reps, you might do 18 on a good day and 15 on a tougher day. Both are valuable, and both contribute to your progress.
This flexibility also applies to how close you push to failure. On days when you feel great, you might push closer to failure. On days when you’re recovering from a hard previous session, you might leave more reps in reserve. This adaptive approach helps you train hard while respecting your body’s recovery capacity.
The Bottom Line on Reps in Reserve
Reps in reserve during high rep training is genuinely useful. It allows you to accumulate training volume without excessive fatigue accumulation. It improves your recovery between sessions, which means you can train more frequently. It reduces injury risk by maintaining better form throughout your sets. And research shows that you don’t need to train to complete failure to build muscle effectively.
For high rep training, aim to leave one to two reps in reserve on most of your sets. This provides excellent stimulus for muscle growth while keeping you in a recovered state that allows for consistent, frequent training. Save training to complete failure for occasional final sets or isolation movements where the recovery demands are lower. This balanced approach will help you make steady progress without burning out.
Sources