Should you train to failure? What zero reps in reserve costs

Training to failure means doing reps until you can't complete another one with good form. In terms of reps in reserve, it's zero: nothing left in the tank. It feels productive, and for some exercises it can be. But for most of your sets, stopping a rep or two short gets you nearly all the benefit for much less fatigue.

What the research says

Reviews of the studies (such as Grgic and colleagues, 2022) found that sets taken to failure and sets stopped a few reps short build similar muscle and strength when the total work is matched. Getting close to failure matters; reaching it every time doesn't add much. What failure does add is fatigue, which slows recovery for your next session.

The real cost of failure

• Longer recovery. Sets to failure leave you more tired for a day or two, which can cost reps in your next workout.
• Worse sets after it. Failing on your first set usually means fewer reps on every set after.
• More risk on big lifts. A failed rep on a heavy squat or bench needs safety bars or a spotter.

When failure is fine

• Dumbbell lateral raiseSide delts
• Dumbbell curlBiceps
• Cable pushdownTriceps
• Leg extensionQuads
• Push-upChest
• Calf raiseCalves

Isolation, machine and bodyweight exercises are safe to take to failure, and doing so on the last set now and then teaches you what zero reps left really feels like. That makes your other effort ratings more honest.

A simple rule

1. Big lifts: stop with 1 to 3 reps left.
2. Small lifts: 0 to 2 reps left, failure on the last set if you like.
3. Later in a training block, get closer to failure; then deload.

Liftsmith sets the reps to leave in the tank for each week of your block and adjusts from what you report after each set. A rating of 0 reps left is marked as a set to failure, in the app and in your exported sets, so you can see how often you really go there.