Meditation can be practised in all positions - lying, sitting, standing and walking.
As long as you remain alert and aware, the position does not matter. If you are alert and aware and your position is not a good one, your body will soon let you know.
Ideally we should be meditating all the time - remaining alert, aware and present whatever we are doing. Using all positions for formal meditation periods helps us to extend the meditative state beyond our formal sitting times.
That said, if you are physically tired and you lie down or use a supported position, the body is bound to take the opportunity for RRR
peace and joy
