Reps in Reserve and Injury Prevention: What You Need to Know
When you’re lifting weights or doing any kind of strength training, one of the biggest questions is how hard should you push? Should you go all out until you can’t do another rep, or should you hold back a little? The answer might surprise you – holding back could actually be better for keeping you healthy and injury-free.
What Are Reps in Reserve?
Reps in Reserve, or RIR, is a simple way to measure how much effort you’re putting into an exercise. It answers one basic question: how many more repetitions could you have done before your form breaks down? If you’re doing a set of squats and you stop when you could have done three more good squats, then you have three reps in reserve.
This concept came from powerlifting coach Mike Tuchscherer in the early 2000s. He wanted a better way for lifters to gauge their effort without having to go to complete failure every single time. The idea caught on because it’s practical and it works.
How RIR Helps You Stay Healthy
The connection between RIR and injury prevention comes down to one key principle: fatigue management. When you train to failure on every set, your body accumulates a lot of fatigue. This fatigue doesn’t just make you tired – it actually changes how your muscles work and how your nervous system functions.
Research shows that training to failure results in similar muscle-building adaptations compared to stopping short of failure. The difference is that when you train to failure, you end up more fatigued and sore. This extra fatigue can interfere with your recovery and your ability to train well in your next workout.
Think about it this way: if you do a heavy upper body workout on Monday and take every set to failure, your muscles will be very sore and your nervous system will be suppressed. When you come back for another upper body session on Thursday, you won’t be able to perform as well. Your strength will be down, your coordination might be off, and you’re more likely to make mistakes with your form. Poor form is one of the biggest risk factors for injury.
The Fatigue Problem
When you accumulate too much fatigue from training to failure repeatedly, several things happen that increase injury risk. First, your movement quality suffers. Your muscles are tired, so they can’t stabilize your joints as well. Your nervous system is fatigued, so your coordination and proprioception – your sense of where your body is in space – gets worse. This combination makes you more vulnerable to strains, sprains, and other injuries.
Second, excessive fatigue can suppress your immune system and slow down your recovery. This means your body has less resources available to repair the damage from training and to adapt to the stress you’re putting on it.
Third, when you’re fatigued, you’re more likely to compensate with other muscles or joints. For example, if your legs are exhausted, you might start using your lower back more to help with a movement. This puts stress on areas that aren’t designed to handle that load, leading to injury.
How to Use RIR for Injury Prevention
The practical application is straightforward. For compound exercises like squats, deadlifts, and bench presses, you should typically leave one to three reps in the tank. This means stopping your set when you could still do one to three more repetitions with good form.
For isolation exercises – the smaller, single-joint movements – you can be more aggressive. You can take the last set of isolation work to failure if you want, since these exercises don’t tax your nervous system as heavily and don’t create as much systemic fatigue.
This approach gives you several advantages. You still build muscle and get stronger because the stimulus is still there. But you don’t accumulate as much fatigue, so you recover better between workouts. You can train more frequently and with better quality. Your form stays better throughout your training week. And because your form is better and you’re fresher, your injury risk goes down.
The Research Behind It
Studies have shown that people are actually quite good at estimating their reps in reserve, especially with practice. One study found that participants had a high degree of accuracy in estimating how many reps they had left in the tank. Even better, as they got more fatigued during a workout, they became even more accurate at this estimation. This means that as you practice using RIR, you get better at it.
The data also shows that training with RIR can result in more total volume over a training week compared to training to failure. In one comparison, training to failure resulted in 22 total reps across three sets, while training with an RPE of 9 (which is about one rep in reserve) resulted in 26 total reps. This is because you recovered better between sets and could maintain your performance better.
The Bigger Picture
While RIR is just one tool, it fits into a larger framework of smart training. Structured injury prevention programs in general can reduce sports injury risk by 30 to 50 percent. These programs often include specific exercises for weak areas, mobility work, and smart programming – which includes managing fatigue through tools like RIR.
The key insight is that you don’t have to destroy yourself in every workout to make progress. In fact, training smarter often beats training harder. By using RIR to manage your fatigue, you can train more consistently, maintain better form, and ultimately stay healthier while still building muscle and getting stronger.
Sources
https://floridasportsinjury.com/5-exercises-to-prevent-sports-injuries-2025-guide/
https://www.empower.physio/blog-all/rpe-vs-rir-1
https://www.therunningweek.com/post/should-runners-lift-heavy-or-light-weights