In the Anapanasati Sutta what is meant by 'sensitive to rapture/bliss'?

Considering these verses of the Anapanasati Sutta > He trains himself, 'I will breathe in sensitive to rapture.' He trains > himself, 'I will breathe out sensitive to rapture.' > > He trains himself, 'I will breathe in sensitive to pleasure.' He > trains himself, 'I will breathe out sensitive to pleasure.' In the commentaries I have read rapture and pleasure (bliss) are taken as jhana factors as detailed here . What exactly is been suggested here? Is it possible to experience these factors in meditation without being in the jhanas and maybe encourage them? Can one encourage them by focusing on them and almost willing them into being? I was always told this was counterproductive. Presumably this part of the sutta is samatha. Is it being suggested that you should be in the jhanas before going on any further in this meditation? I think generally I'm just wanting some additional explanation to what these verses mean and the implication of them to meditation practice.