فَإِنْ لَمْ يَسْتَطِعِ الرُّكُوعَ وَالسُّجُودَ أَوْمَأَ إِيمَاءً، وَجَعَلَ السُّجُودَ أَخْفَضَ مِنَ الرُّكُوعِ، وَلَا يَرْفَعُ إِلَى وَجْهِهِ شَيْئًا يَسْجُدُ عَلَيْهِ.
Translation: If unable to bow and prostrate, the patient makes gestures, lowering the head more for prostration than for bowing, and does not raise an object before the face to prostrate on.
Ima' is the movement of the head standing in for bowing and prostration. The two gestures must remain distinguishable.