I wonder if even a certified climbing helmet would be of much use when rocks start falling from the sky.
I have seen mention of fracture injuries in a number of articles about this eruption. I'm curious if they were caused by rocks ejected into the air? Then again, panic could lead people to slip and fall as they fled the eruption in haste, and if you notice in the videos, many of the hikers are rather advanced in age and generally more prone to fractures.