The RIR strength method is the simple way to know if you’re lifting heavy enough – for real results
To build lasting muscle and strength, you’ll likely know you need to challenge yourself in the gym. Scroll through FitTok and you’ll find trainers preaching the importance of pushing hard on every lift.
Of course, there’s a fine line when it comes to effort. If you’re constantly training too intensely, you risk burnout and injury. But if you’re not working hard enough, you might not see the results you’re aiming for. That’s where the reps in reserve – or RIR – method comes in.
RIR is a way of measuring effort that’s changing how everyone from beginners to elite athletes approaches strength training. Even fitness creators on social media are praising it. One user says it helps account for how you’re feeling on a given day so you can train at the right intensity. ‘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 claims the method will ‘unlock better workout intensity and consistency’ and ‘improve muscle growth and strength’.
While viral claims like these are often overblown, RIR is a legitimate approach. 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 have done two more reps before failure, you were at 2 reps in reserve.
You can think of it as the strength-training equivalent 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 on a scale from one to 10 (one being very easy and 10 being maximum effort).
For example:
RPE 10 = 0 RIR (failure)
RPE 9 = 1 RIR
RPE 8 = 2 RIR
RPE 7 = 3 RIR
‘The value of RIR is that it adjusts to your day-to-day readiness better than fixed percentage prescriptions alone,’ Reiner says. If you’re aiming for an RPE of 8 during a set of eight reps, you might hit that effort level by rep five on a tough day. On a good day, you might reach 10 reps before hitting the same level.
With the RIR method, the focus shifts away from strict rep targets – which research suggests matter less for muscle growth than once thought – and towards effort, which is the main driver of strength and muscle gains.
While RIR can work for most people, Bomgren says it’s best suited to those with some training experience. It’s easier to estimate how close you are to failure if you’ve been lifting consistently for a while.
If you’re new to strength training, you’re still learning what your body can do. In that case, Bomgren suggests focusing on movement quality first, using simple cues like ‘easy’, ‘challenging’ or ‘very hard’ instead of RIR.
Once you’ve built a consistent routine and developed a feel for effort, RIR becomes more useful. ‘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 training
To estimate your RIR after a set, ask yourself: ‘If I had to, how many more reps could I have done with good form?’
For example, say you complete 10 goblet squats. The weight feels challenging, your final reps slow down, but your form stays solid. If you think you could have done 2 or 3 more reps, your RIR is 2-3.
Bomgren recommends aiming for around 2-3 reps in reserve for most sets. ‘This range recruits the muscle fibres needed to build strength without overdoing it, allowing for better recovery, fewer injuries and more consistency.’
RIR can also help guide your progression. If you complete a set easily and still feel like you have several reps left in reserve, it may be time to increase the weight.
The benefits of using reps in reserve
It may help reduce injury risk
RIR helps you better manage fatigue, says Reiner. ‘Pushing every set to failure comes with a cost. It affects recovery and can impact performance later in the session or week.’
It tailors training to you
There’s a lot of focus on lifting heavy in low rep ranges right now, says Bomgren. But that doesn’t always translate well for the general population.
‘The general population isn’t conditioned to lift heavy in those smaller rep ranges, and doing so could lead to injury,’ she says. ‘In my opinion, the goal 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.’
Research shows muscle can be built across a wide range of reps – anywhere from 1-30 – so RIR allows you to choose weights that suit your level and feel less intimidating.
It builds strength and muscle
As long as recovery and nutrition are in place, RIR can help target different adaptations depending on your goals.
For muscle growth, you generally want to train close to failure, but not necessarily reach it. ‘A practical, evidence-based range for hypertrophy is usually about 0-3 RIR, with many people doing well around 1-2 RIR,’ says Reiner.
For strength, staying slightly further from failure can help maintain technique and training quality. ‘A practical range here is usually 2-5 RIR, especially for compound lifts,’ she adds.
RIR helps you apply enough effort to drive progress without unnecessary fatigue.
It helps you stay consistent
Managing fatigue is key to long-term consistency. ‘Finishing a set with 2-3 RIR allows you to train close enough to failure to build muscle without completely exhausting yourself,’ says Bomgren.
That balance makes it easier to recover properly and stick to a routine over time.
Tips for making the most of RIR
- Start with simpler movements like leg presses and bicep curls before applying RIR to more complex lifts
- Aim for 2-3 reps in reserve for most sets
- Don’t chase exhaustion – more fatigue doesn’t mean better results
- Test your limits every few months by safely pushing closer to failure
- Adjust RIR depending on the exercise – stay further from failure on big lifts and closer on isolation work
- Prioritise good form and pain-free movement at all times
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Danielle Zickl is a freelance writer who has 10 years of experience covering fitness, health, and nutrition. She’s a graduate of Ithaca College. You can find her work here on Women’s Health, and in many other publications including PS, SELF, Well+Good, Runner’s World, Outside RUN, Peloton, Men’s Fitness, and more.
