While in Jhāna to walk or (reaching) Jhāna is not possible while walking?

How could one come, if any experiances and understanding, to the idea that one in Jhana isn't able to walk, not to speak of to listen and talk? Maybe there is a different between sitting, standing, walking, lying down? And what did the Sublime Buddha taught and tell about it? What would be the effect on Satipatthana is such ideas would be correct? Bond to sit, 7 days, weeks, month, years... or how would a living one quick react? And refined: would an on-house-holder be able to undertake a jhanic walk-about? Could a wanderer of other sects, say one on the Jakobs-path gain 'accidently' Jhana while developing the Brahma-Viharas?