How Useful Is Reps in Reserve on Days You Feel Low Energy
We all have those days. You wake up tired, your body feels heavy, and the thought of hitting your usual workout intensity makes you want to crawl back into bed. This is where understanding Reps in Reserve, or RIR, becomes genuinely valuable for your training.
Reps in Reserve is a simple concept. It means the number of repetitions you could theoretically perform before reaching complete muscular failure. If you’re doing a set of squats and you stop with three reps left in the tank, you’re training at an RIR of 3. On low energy days, this metric becomes your best friend because it lets you adjust your training without abandoning your workout entirely.
The traditional approach to training often pushes people toward failure. Go hard or go home, right? But research shows this isn’t necessary. Training to failure on average produces similar strength and muscle-building adaptations compared to stopping short of failure. The catch is that training to failure leaves you in a worse recovery state. When you’re already feeling depleted, this becomes a real problem. You’re adding extra fatigue to a system that’s already struggling.
This is where RIR shines on low energy days. Instead of pushing to failure and digging yourself deeper into a hole, you can maintain your training structure while respecting what your body is telling you. If you normally train at an RIR of 1 or 2, bumping up to an RIR of 5 or 6 on a tough day keeps you moving without crushing your recovery further.
The beauty of using RIR is that it gives you permission to train smart rather than hard. You’re not skipping the gym. You’re not abandoning your program. You’re simply adjusting the intensity dial based on real-time feedback from your body. This approach actually leads to better long-term results because you can train more frequently when you’re not constantly hammering yourself into the ground.
For compound movements like squats, bench presses, and deadlifts, keeping at least one or two reps in reserve on low energy days is particularly smart. These movements demand more from your nervous system and joints. Pushing them to failure when you’re already fatigued increases injury risk and extends recovery time unnecessarily. Isolation exercises and machine work are more forgiving, so you have slightly more flexibility there.
The data backs this up. When comparing training approaches, people who use RIR strategically often perform more total reps across their workout compared to those grinding to failure on every set. This happens because they maintain better performance across multiple sets. On your first set, you might hit 9 reps at an RIR of 1. On your second set, you’re already fatigued and only manage 7 reps. By your third set, you’re down to 5 reps. That’s 21 total reps. But if you had started at an RIR of 2, you might hit 9 reps on set one, 9 on set two, and 8 on set three. That’s 26 total reps with less accumulated fatigue.
The practical application is straightforward. On days when you’re running on empty, aim for an RIR of 4 to 6 on your main lifts. This keeps you in a productive training zone without excessive fatigue accumulation. You’re still creating a stimulus for adaptation. You’re still maintaining your training frequency. But you’re not adding unnecessary stress to an already compromised system.
One important note: RIR works best when you’re honest with yourself about how you’re actually feeling. It’s easy to convince yourself you’re more tired than you are, and it’s equally easy to push harder than you should. The goal is finding that middle ground where you’re training with intention but not desperation.
The real value of RIR on low energy days is that it removes the all-or-nothing mentality from training. You don’t have to choose between crushing yourself or skipping the workout. You can show up, do quality work at an appropriate intensity, and still recover properly. Over weeks and months, this consistency matters far more than any single heroic training session.
Sources
https://runlovers.it/en/2025/strength-for-runners-heavy-weights/
https://www.elevaterope.com/blogs/articles/rate-of-perceived-exertion
https://www.womenshealthmag.com/uk/fitness/a69069732/training-formula-for-women-strength-longevity/
