This Fitness Tool Will Help You Gain Strength Fastjacoblund – Getty Images
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To build lasting muscle and strength, you’re probably well aware you need to challenge yourself in the gym. Take a scroll through FitTok, and you’ll find trainers preaching the importance of pushing hard each and every lift.
Of course, there’s a fine line when it comes to effort. If you’re constantly working out too intensely, you risk burnout and injury. But if you’re not working out hard enough, you might not see the gains you’re hoping for. That’s where the reps in reserve, or RIR, method comes in.
RIR is a measurement of effort that’s revolutionizing how everyone from beginners to elite competitors approaches strength training. Even fitness creators on social media are singing its praises: One user says it does a good job at taking into account how you’re feeling on a specific day so you can train at the optimal load. “On a strong day you may lift a bit more than expected, on an off day you may lift a little less—but either way you train at the right level for the day,” they say. Another user promises this method will “unlock better workout intensity and consistency” and “improve muscle growth and strength.”
While viral claims like these are often too good to be true, RIR is the real deal. Here’s why.
What is Reps in Reserve?
RIR is “a great way to measure how hard you’re working during a set,” says Lindsey Bomgren, CPT, founder of Nourish, Move, Love. “Instead of just counting reps, you’re asking yourself, ‘How many more reps could I have done before physically failing or losing proper form?’” For example, if you finish a set and feel like you could’ve done two more reps before hitting failure, you were at 2 reps in reserve, she explains.
You can think of it as the resistance-training version of rate of perceived exertion (RPE), according to Susie Reiner, PhD, assistant professor of exercise and sport science at Seton Hall University and founder of TheoryEx. RPE measures how hard you feel you’re working during physical activity on a scale of one to 10 (one being not hard at all and 10 being max effort).
For instance:
And so on. “The value of RIR is that it adjusts to your day-to-day readiness better than fixed percentage prescriptions alone,” Reiner says. Say you’re supposed to hit an RPE of 8 during a set of 8 reps. On a bad day, you might feel like you’ve hit that effort level by rep 5. On a good day, you might cruise to 10 reps and feel like you’ve only just hit it.
With the RIR method, you’re worried less about the actual rep scheme—which research has found matters less for muscle growth than once thought— and more about effort, the main driver of muscle and strength gains.
While RIR can work for almost anyone, Bomgren says it’s best utilized for intermediate to advanced fitness levels or those who have a solid training foundation. That’s because it’s easier to estimate how close you are to failure if you’ve been lifting for a long time.
If you’re new to strength training, you’re likely still getting a feel for what your body is capable of, and focusing more on movement quality before intensity, Bomgren says. “It’s probably better to measure exercises and weights by ‘easy,’ ‘challenging,’ or ‘very hard’ versus RIR” until you gain more experience.
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Once you’re built a consistent routine and develop a feel for effort, RIR becomes especially useful, Bomgren continues. “It allows you to dial in the weights you’re using and push yourself. And if you’re more advanced, RIR is a great way to know when you can push heavier weights while still managing fatigue and recovery, and progressing [overload].”
How to Use Reps in Reserve in Your Own Training
To calculate how many reps you have in reserve after a set, ask yourself: “If I had to, how many more reps could I have done with good form?”
Say you do 10 dumbbell goblet squats. You feel challenged by the weight and you slowed down during your last 1 to 2 reps, but you weren’t completely spent, and your form stays solid. If you think you could’ve done 2 to 3 more reps at that weight with good form, your RIR is 2 to 3.
Bomgren recommends aiming for around 2 to 3 reps in reserve on most sets. “This range recruits the muscle fibers needed to build strength without overdoing it, allowing for better recovery, fewer injuries, and maintaining a consistent fitness routine.”
RIR can also help you track progress and adjust your weight selection as you get stronger, Reiner says. For example, if you breeze through 12 bicep curls and still feel like you have 5 reps in reserve, it might be time to “re-evaluate and increase your weights,” Bomgren says.
The Benefits of Using Reps in ReserveIt May Help Reduce Injury Risk
You can better manage muscle fatigue using RIR, according to Reiner.
“Pushing every set to failure comes with a cost,” she says. “It affects [muscle] recovery and can impact performance later in the session or week.”
It Tailors Your Training to You
There’s a lot of discourse about lifting heavy in small rep ranges to build muscle right now, Bomgren says. But what often gets lost is how that advice applies to the general population in a practical way.
“The general population isn’t conditioned to lift heavy in those smaller rep ranges, and doing so could lead to injury,” Bomgren says. “In my opinion, the name of the game is to stay in the game, injury free. I love the RIR model as it’s more tailored to meet individuals where they are at in their fitness journey versus assigning a specific rep range to build muscle. We know muscle can be built across a wide range, anywhere from 1 to 30 reps, so RIR allows individuals to choose weights that fit their fitness level—and might feel less intimidating.”
It Builds Muscle Strength and Size
As long as you’re also properly nourishing yourself and recovering, of course. Using RIR can help target different muscle adaptations based on your goals, according to Reiner.
For muscle hypertrophy, you generally want to be somewhere close to failure, but not necessarily at failure, Reiner advises (and recent research supports this). “A practical, evidence-based range for hypertrophy is usually about 0 to 3 RIR, with many people doing well around 1 to 2 RIR on most working sets,” she says. “Going all the way to 0 RIR every set is usually not necessary and often increases fatigue more than it improves results.”
For strength, you don’t need to be quite as close to failure. “In fact, staying a bit further from failure often allows you to maintain speed, technique, and overall training quality,” she says. “A practical range here is usually 2 to 5 RIR, especially for compound lifts (exercises that engage multiple joints and muscle groups at the same time).”
RIR is useful because it helps you apply enough effort to drive results without creating unnecessary fatigue, Reiner adds.
It Helps You Stay Consistent
This methodology can really help mitigate recovery demands and improve long-term consistency in the gym. “I can say you should finish a working set with 2 to 3 RIR, which allows you to train close enough to failure to build muscle without totally exhausting yourself, which can require longer recovery and inhibit workout consistency,” Bomgren says.
That matters because excessive fatigue can require more recovery time and make it harder to stick to a routine. “Consistency is what I’m truly after as a trainer with my clients. I’m looking for a consistent lifting routine to build long-term strength.”
Tips for Making the Most of Reps in Reserve
Ready to give RIR a go? Here are a expert-backed tips to keep in mind:
Start with simpler movements. It’s easier to learn RIR doing straight-forward exercises like leg presses and bicep curls before applying it to more technical lifts, Reiner says.
Aim for 2 to 3 reps in reserve in most sets. Bomgren says this is challenging enough to be effective yet sustainable.
Don’t chase exhaustion. More fatigue is not the goal, Reiner says.
Test your limits every few months, according to Reiner and Bomgren. Take a set closer to failure than you normally would—safely—to check if your RIR estimates are still accurate.
Don’t use the same RIR target for every exercise. Reiner suggests staying a bit further from failure on big compound lifts and getting closer on smaller isolation exercises, where injury risk is lower.
Prioritize form and pain-free movement above all else, Bomgren says.
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