Their methodology is scientific: They've observed head bangers, conducted focus groups and used biomechanical analysis. Their conclusion is comedic in a "No shit, Sherlock" kind of way:
"To minimise the risk of head and neck injury, head bangers
should decrease their range of head and neck motion, head bang to
slower tempo songs by replacing heavy metal with adult oriented rock,
only head bang to every second beat, or use personal protective
equipment."
The full read -- including an analysis of the injuries
that would be experience by cartoon characters Beavis and Butt-head based
on their theoretical model -- can be found here.
-- Unreal