If you’ve ever lifted weights, you’ve probably asked yourself this question: Do I need to train until I can’t do another rep? New research from Florida Atlantic University and collaborators sheds light on that very issue, offering some useful guidance for anyone trying to build muscle or gain strength.
The study, published in Sports Medicine, looked at how training close to failure—or stopping short of it—affects changes in muscle size and strength. This “distance from failure” is measured using a concept called repetitions in reserve (RIR).
For example, if you stop a set and could still do three more reps, your RIR is 3. Training to failure would mean doing reps until your muscles physically can’t lift anymore—an RIR of 0.
To better understand how RIR influences results, researchers examined data from 55 different studies. They focused on how close people got to failure while training and how that impacted muscle growth (hypertrophy) and strength. Importantly, they only looked at the main muscles used during each exercise. So, for a leg press, they focused on quadriceps growth.
The results? When it comes to strength, it doesn’t really matter how close you get to failure. Whether you stop several reps short or push yourself to the limit, the improvements in strength are roughly the same.
But for muscle growth, training closer to failure does seem to help. The fewer reps left in the tank when you stop a set, the more muscle you’re likely to build—up to a point.
Dr. Michael Zourdos, senior author of the study, explained, “If you’re aiming for muscle growth, training closer to failure might be more effective. The total number of sets or reps matters less than how close you come to failure during each set.”
The researchers recommend that people aiming to build muscle train within 0 to 5 reps of failure. That range allows for enough effort to trigger growth, while still leaving some room to avoid unnecessary fatigue or injury.
On the other hand, those focused purely on strength should prioritize heavier weights and not worry so much about reaching failure. In fact, stopping 3 to 5 reps short of failure is likely ideal for gaining strength without overtaxing the body.
Dr. Zac Robinson, the study’s first author, added another benefit of training near failure—it improves how accurately people can judge their effort. When you train close to your limit, you get better at estimating how many reps you truly have left. That matters, because if you underestimate, you might train too lightly and not get the results you want.
Interestingly, the researchers also noted that training closer to failure may better mimic the demands of a max strength test—like a one-rep max bench press. That’s because the movement patterns and mental effort are more similar to what’s needed during an actual strength test.
Still, the researchers point out that training to failure isn’t always easy—or ideal. It can be physically and mentally draining, and recovery takes longer. If done too often, it could actually hurt your long-term progress by increasing fatigue and reducing performance in later workouts.
So, what’s the practical takeaway? For muscle growth, pushing close to failure seems to offer better results, especially if you’re keeping your training volume manageable. But for strength, going all the way to failure isn’t necessary—and stopping a few reps early is just as effective, especially when paired with heavier weights.
In other words, you don’t have to go “all out” in every set to get results. If you’re training smart, being consistent, and adjusting your approach based on your goals—muscle size or strength—you can still make great progress without always hitting the wall.
This study adds clarity to a long-running debate in fitness, offering real-world advice for athletes, lifters, and everyday gym-goers alike.
And while more research is needed to understand the exact relationship between effort and gains, one thing is now clearer than ever: you don’t always need to hit failure to succeed—but sometimes getting close can help, especially if you’re looking to grow.
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The research findings can be found in Sports Medicine.
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