In resistance training, performing sets to muscular failure does not produce significantly greater strength gains compared to performing sets with repetitions remaining in reserve.

Study: Divergent Strength Gains but Similar Hypertrophy After Low-Load and High-Load Resistance Exercise Training in Trained Individuals: Many Roads Lead to Rome.

This study found that whether you lift heavy weights for few reps or light weights for many reps — as long as you go all the way to exhaustion — you get about the same strength gains. That suggests going to failure isn’t what makes you stronger; it’s just one way to train.

Study: Effect of resistance training to muscle failure vs non-failure on strength, hypertrophy and muscle architecture in trained individuals

This study found that lifting weights until you can't do another rep doesn't make you stronger than stopping a few reps before failure — both ways worked just as well for building strength.

Study: Resistance training leading to repetition failure increases muscle strength and size, but not power-generation capacity in judo athletes

The study found that lifting weights until you can't do another rep didn't make people stronger than stopping a few reps before failure—both methods worked just as well for building strength.

Study: Exploring the Dose–Response Relationship Between Estimated Resistance Training Proximity to Failure, Strength Gain, and Muscle Hypertrophy: A Series of Meta-Regressions

The study found that pushing to absolute failure on every set doesn’t make you significantly stronger than stopping a few reps short, which supports the idea that going to failure isn’t necessary for strength gains.