On "Heavy" armor:

If somebody falls from their horse and can't get up before they are killed, it's almost certain that they didn't have time to actually say what was wrong with them either. It seems more likely to me that anyone who falls off a horse in armor (or out) might just break a bone or take some other kind of injury that would make movement in any equipment horribly difficult. If someone breaks one of their vertebrae in a fall and struggles to get up, it might look like they are fighting against the weight of their armor.