How Hard Should You Actually Train? Why Leaving Reps in the Tank Beats Grinding to Failure

The most freeing idea in the newest strength-training guidelines is one a lot of committed lifters resist on first reading: you do not have to train to failure to get strong. That is not a licence to coast, but it does mean that taking a set all the way to the point where the bar stops moving buys you almost nothing for one of the two things most people chase in the gym. The effort still has to be real. It just does not have to end in a grind.

That is not a motivational line. It is the considered position of the largest evidence review the field has produced in nearly two decades, and it changes how a busy person in Riyadh should think about every working set they do.

The rulebook that finally caught up

In early 2026 the American College of Sports Medicine published its first full Position Stand on resistance training in 17 years, synthesising 137 systematic reviews covering more than 30,000 participants (ACSM Position Stand, 2026). The headline is not a new exercise or a clever set-and-rep scheme. It is a change in the language itself. The old guidance talked in rigid percentages of your one-rep maximum. The new one talks in effort, measured as reps in reserve, and it says plainly that training to momentary muscular failure did not consistently improve outcomes for the average healthy adult.

Read the practical translation and it is almost startling in its simplicity: lift with real intent, stop a couple of reps short of the point where your form falls apart, and you get the same results with less fatigue. Consistency, the document argues, beats complexity, and the best programme is the one you will actually keep doing. For anyone who has spent years believing that a set only counts if it ends in a grimace, that is a quiet revolution.

What "reps in reserve" really means

Reps in reserve, or RIR, is simply how many more repetitions you could have completed before failing. Finish a set of squats certain you had three good reps left in you, and that set was taken to 3 RIR. Grind out the last rep with nothing behind it and you hit 0 RIR, which is failure. Proximity to failure is just the same idea worn the other way round.

The reason this framing matters is that it turns effort into something you can dial, rather than a binary of "did I collapse or not". And once you can put a number on effort, you can ask the question the research has spent the last decade answering: how close to the edge do you actually need to work?

The evidence that failure is optional

Start with muscle size, because that is where most people assume failure is non-negotiable. Refalo and colleagues pooled 15 studies comparing sets taken to failure against sets stopped short, and found a trivial advantage for going to failure, an effect size of just 0.19 (Refalo et al., 2023). When they isolated true momentary failure against stopping a few reps early, the advantage disappeared altogether. Sets that end before the wheels come off grow muscle about as well as sets that end in a fight.

Grgic and colleagues came at the same question from the strength angle and reached a compatible answer. Across their meta-analysis there was no significant difference between failure and non-failure training for either strength or hypertrophy (Grgic et al., 2022). They were honest about the texture in the data, mind you: in trained lifters specifically, failure nudged hypertrophy in its favour, and when studies did not equate total volume the non-failure groups actually gained slightly more strength. This is not a field of clean, tidy verdicts. But the weight of it points one way. For most people, most of the time, failure is a choice, not a requirement.

The split almost nobody trains around

Here is the part that made me stop and re-read the paper, and I suspect it will do the same to a fair few coaches who think they already know this topic cold. Strength and size do not respond to effort in the same way.

Robinson and colleagues ran a series of meta-regressions specifically to map the dose-response curve of proximity to failure (Robinson et al., 2024). For muscle growth, the relationship was real and directional: hypertrophy increased as sets were terminated closer to failure. For strength, though, the slope was essentially flat. The relationship between how close you trained to failure and how much stronger you got contained a null point, meaning it was negligible. You can leave a genuinely large amount in the tank and still gain strength at close to full tilt.

Sit with what that means for programming. Most coaches, myself included for a long stretch, treat "train hard" as a single dial you turn up for everything. The data says it is two dials. If your goal is maximum size, working nearer to failure earns you a little extra. If your goal is strength, chasing failure is largely wasted currency, and worse, it is currency you pay for in fatigue that eats into your next session. That distinction is not in most gym lore, and it should be.

Your reps in reserve are probably wrong (and that is fine)

There is a catch that keeps this from being a licence to sandbag every set, and it is one of the most useful findings in the whole area. People are bad at judging how close to failure they are, and they are bad in a specific direction.

Hackett and colleagues had trained lifters estimate their reps to failure, then made them prove it by lifting to the end (Hackett et al., 2017). When people were genuinely close, within about five reps of failure, their guesses were accurate to roughly a single rep. But the further from failure they were, the worse it got: at seven to ten reps out, they were off by more than two reps, and they consistently underestimated how much they had left. In plain terms, when you feel like you have three reps in reserve, you may well have five. The tank is fuller than the driver thinks.

That cuts both ways, and both ways are encouraging. It means the person who thinks they are miles from failure is usually closer than they feel, so their "easy" sets are doing more than they credit. And it means that if you aim to stop at two or three reps short, the natural human tendency to leave two or three reps less than you intended lands you in a safe, productive window rather than a lazy one. The honest instruction is not "go to failure". It is "get somewhere in the neighbourhood, and trust that neighbourhood".

What this means for your training week

Translate all of this into something you can act on tomorrow. The new guidelines give clean targets, and the effort research tells you how to spend your energy within them.

• Chasing strength? Lift heavy, around 80% of your one-rep max, for two to three sets on your main lifts, and stop with two or three reps still in you. The evidence says you will get almost all the strength on offer without the grind.
• Chasing size? Aim for roughly 10 or more hard sets per muscle group across the week, and here it pays to work a touch closer to failure, one to two reps out. Loads anywhere from 30% to 100% of your max all build muscle, provided the effort is there.
• Judging effort? If your last rep slowed to a crawl and your technique started to drift, you were near enough. If it moved fast and clean, you probably had more than you think, so add a rep or a little load next time.

The autoregulation this unlocks is the real prize, and it is why I lean on effort-based targets when I build a client's periodised programme. A percentage on a page does not know you slept badly or that it is 46 degrees outside. A reps-in-reserve target does, because it flexes with the day: on a strong morning your 2 RIR set is heavier, on a flat one it is lighter, and the training effect stays honest either way.

That matters more here than almost anywhere. The Riyadh professional I coach is often short on sleep, long on stress, and training through a summer that makes recovery harder than the numbers suggest, something I dug into in why your training feels harder in the heat. Taking every set to failure in that context is a fast route to a body that is always slightly wrecked and never quite adapting. Leaving reps in reserve is how you keep the quality high across two or three sessions a week rather than blowing yourself apart in one. If you needed the case for training smart on a light schedule, I made it in full in the weekend warrior piece.

Strength was never about how much you can suffer inside a single set. It is about how much good, repeatable work you can stack up over months without breaking yourself to do it, and the science has finally caught up to what the best coaches quietly always knew.

Frequently Asked Questions

Do I need to train to failure to build muscle?

No. Refalo et al. (2023) found only a trivial advantage for training to failure over stopping a few reps short, and no advantage at all once true momentary failure was isolated. Working close to failure, roughly one to two reps in reserve, builds muscle about as well with far less fatigue.

What does "reps in reserve" mean?

Reps in reserve (RIR) is how many more repetitions you could have done before failing. If you stop a set believing you had three reps left, that is 3 RIR. It is a way of measuring effort by how close you came to the edge, rather than by the load on the bar.

How many reps should I leave in the tank?

For strength, two to three reps in reserve captures nearly all the benefit, because Robinson et al. (2024) found proximity to failure has a negligible effect on strength gains. For muscle size, working slightly closer, one to two reps in reserve, gives a small edge.

Is training to failure ever worth it?

Occasionally, and mostly for hypertrophy in trained lifters, where Grgic et al. (2022) saw a small favourable effect. It is best used sparingly on safer, single-joint movements, not on heavy compound lifts where the fatigue and technique cost outweighs the gain.

How do I know how close to failure I really am?

Most people underestimate how many reps they have left, especially when far from failure (Hackett et al., 2017). A reliable cue is bar speed: when your reps slow noticeably and your form starts to change, you are within one to two of failure. If they are still moving fast, you have more in reserve than it feels.

References

1. American College of Sports Medicine. Resistance Training Prescription for Muscle Function, Hypertrophy, and Physical Performance in Healthy Adults: An Overview of Reviews (Position Stand). Medicine & Science in Sports & Exercise. 2026;58(4). acsm.org
2. Refalo MC, Helms ER, Trexler ET, Hamilton DL, Fyfe JJ. Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-analysis. Sports Medicine. 2023;53(3):649-665. doi:10.1007/s40279-022-01784-y
3. Robinson ZP, Pelland JC, Remmert JF, Refalo MC, Jukic I, Steele J, Zourdos MC. Exploring the Dose-Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions. Sports Medicine. 2024;54(9):2209-2231. doi:10.1007/s40279-024-02069-2
4. Grgic J, Schoenfeld BJ, Orazem J, Sabol F. Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: A systematic review and meta-analysis. Journal of Sport and Health Science. 2022;11(2):202-211. sciencedirect.com
5. Hackett DA, Cobley SP, Davies TB, Michael SW, Halaki M. Accuracy in Estimating Repetitions to Failure During Resistance Exercise. Journal of Strength and Conditioning Research. 2017;31(8):2162-2168. PMID:27787474