Interesting results on latest testing of helmet designs and the protective effect against shock waves. Turns out maybe futuristic helmets should have a "decorative" ridge !
https://scitechdaily.com/shocking-results-when-wwi-helmets-were-compared-to-modern-military-designs/
https://scitechdaily.com/shocking-results-when-wwi-helmets-were-compared-to-modern-military-designs/