Before set 1 of a strength exercise, tap + Warm-up (Train, at the top of the exercise) or the round Warm-up button (Focus mode). Each tap adds one more, lighter set in front.

• Each warm-up's weight and reps are filled in for you, lighter than the set after it.
• The rest after a warm-up is shorter than your normal rest.
• Warm-ups don't count toward progress and are never saved.

To make warm-ups lighter or heavier, or change their rest, go to You → Warm-up sets. The example there updates as you type, and what you set is saved as you change it.