The Companions of the Prophet ﷺ complained to the Prophet ﷺ about the hardship when they kept their forearms far away from their sides while prostrating. He said: Take help with the elbows (by spreading them on the ground and sticking them to the sides).  

اشْتَكَى أَصْحَابُ النَّبِيِّ ﷺ إِلَى النَّبِيِّ ﷺ مَشَقَّةَ السُّجُودِ عَلَيْهِمْ إِذَا انْفَرَجُوا فَقَالَ اسْتَعِينُوا بِالرُّكَبِ