Bodyweight

With no plates to add, progress with just your own bodyweight has to come from somewhere else: leverage, range, tempo, or working one side of the body at a time — not a number stamped on a disc. A lunge gets harder by raising the back foot; a side plank gets harder by lifting the top leg; and dips get harder by leaning the torso forward — that lean is exactly what shifts the load from chest to triceps, two different muscles from the same movement depending on how the body is angled. That same lack of equipment is the one thing bodyweight training offers without any condition attached: lunges, leg raises and the side plank all work in an empty room, with no plate or machine to load. Leg raises and the side plank train the core without flexing the spine, unlike a barbell curl, which depends on an external implement just to generate resistance at all. Leverage, though, has a ceiling: at some point changing the angle stops being enough stimulus, and that's the point where adding outside weight is what keeps progress going. That ceiling isn't a flaw in the method — it's just the honest edge of what leverage alone can do.