Definition
Progressively heavier light sets performed before the working sets, to prepare the joints and rehearse the movement without adding fatigue.
A workable ramp for a 100 kg working weight: the empty bar for 8, 40 kg for 5, 60 kg for 3, 80 kg for 2, then the first working set. Four sets, about six minutes, and each one is easy on purpose.
Two rules keep them useful. Reps drop as weight rises, so nothing accumulates fatigue, and the last warm-up should sit within 10 to 20 percent of the working weight so the first hard set does not feel like a surprise.
Heavier work needs more warm-up sets, not more general cardio. A client working at 90 percent needs five or six ramp sets; a client doing 3 x 12 on a leg curl needs one.