Moderate evidence

Training to absolute failure isn't necessary, and for strength it may be counterproductive.

In practice

Stopping one to three reps short of failure gets you almost all of the growth and leaves you far fresher for the rest of the session and the week. For strength work specifically, grinding to failure appears to offer no advantage.

What it doesn't say

Proximity to failure is estimated in most of these studies rather than measured, and people are unreliable judges of how many reps they had left — beginners especially tend to stop well short of where they think they are.

Sources

• Robinson ZP, Pelland JC, Remmert JF, Refalo MC, Jukic I, Steele J, Zourdos MC (2024). Exploring the dose-response relationship between estimated resistance training proximity to failure, strength gain, and muscle hypertrophy: a series of meta-regressions. Sports Medicine, 54(9):2209–2231. doi.org/10.1007/s40279-024-02069-2
• Refalo MC, Helms ER, Trexler ET, Hamilton DL, Fyfe JJ (2023). Influence of resistance training proximity-to-failure on skeletal muscle hypertrophy: a systematic review with meta-analysis. Sports Medicine, 53(3):649–665. doi.org/10.1007/s40279-022-01784-y