As can be read in various sources, for example The Guardian, Russia has put its ‘nuclear deterrence forces’ on high alert.

What does that even mean? Isn’t the point of Mutually Assured Destruction (MAD) that these forces are always ready to go? The article states that it probably doesn’t mean that the bombers are actually being loaded. But I don’t imagine that matters anyway. If MAD wouldn’t work because bombers aren’t ready then it is pointless anyway. What am I missing here?