If you lift weights until you can’t do another rep versus stopping before failure—while doing the same total amount of work—you’ll feel more tired and more worn out during the workout, especially if you’re a regular gym-goer.

Even if you do the same total amount of lifting, going all the way to failure still makes you more tired than stopping short — so it’s not just how much you lift, but how hard you feel you’re working and how often you’re pushing that matters more.

If you lift weights until you literally can't do another rep, you'll feel more tired right after than if you stop a couple reps before failure — even if you're someone who regularly lifts weights.

If you lift weights until you can't do another rep, your body feels like you worked harder than if you stopped before failure—even if you did the same total number of reps and sets.

Lifting weights until you can't do another rep leaves you much more tired during and after the workout than stopping a few reps short — even if both methods build muscle equally.

When trained guys do lots of reps, they feel more tired, weaker longer, and more stressed than when they do fewer heavy reps — even though their muscles are damaged about the same.