Has seen the old myth about scrum caps being a useful took against concussion has re-surfaced. I know we're generally better than that here, but it always bears repeating.
Please note, scrum caps DO NOT reduce risk of concussion, it's not even what they're for (cuts, abrasions, soft tissue injuries). What they can do, is provide a false sense of security that results in increased risk taking, and slightly INCREASE risk of concussion.
The brain is made of soft tissue, which is cushioned by spinal fluid and encased in the protective shell of the skull. When you sustain a concussion, the impact can shake your brain, literally causing it to move around, impacting the inside of your skull. The trauma is suffered by the brain itself, and can be suffered without direct trauma to the head.
Blows to the head that involve an element of traction to the neck, rotation of the head, or setting up a whiplash-type movement are those most likely to result in concussion.
As concussion is an injury sustained inside the skull, padding the outside of the skull (eg a scrum cap) provides no protection from concussion – no more so than padding the back of a cricket bat makes the front any less solid. It is worth noting that you can lose consciousness without suffering concussion, and can suffer concussion without losing consciousness. It is also worth noting that the victim is often the least reliable person to say if a loss of consciousness occurred – remember, amnesia is another sign of concussion. Loss of consciousness itself is considered to mean concussion until proven otherwise, but is far from the only sign to look out for.
If you want to reduce concussion, look at tackle technique, strengthen the neck, improve motor control of the neck muscles and work on your proprioception. Just don't think that 5mm of padding in the wrong place is going to help.
https://pubmed.ncbi.nlm.nih.gov/19127196/
Conclusions: Padded headgear does not reduce the rate of head injury or concussion. The low compliance rates are a limitation. Although individuals may choose to wear padded headgear, the routine or mandatory use of protective headgear cannot be recommended.
https://pubmed.ncbi.nlm.nih.gov/27032915/
Conclusions: Nearly 40% of collegiate rugby players surveyed believed headgear helped to prevent concussions despite no scientific evidence that it does. This misconception about rugby headgear could increase aggressive play. Those who believed headgear prevented concussion were, on average, 4 times more likely to play with increased aggressive form than those who believed headgear did not prevent concussions. This can place all players at increased risk without providing additional protection.
https://pubmed.ncbi.nlm.nih.gov/29081983/
Background/aim: Concussions in rugby union pose a major threat to player welfare. Research has found protective headgear offers no significant protection against concussions but suggests a large proportion of players perceive headgear to be effective in preventing concussions. This study aimed to explore UK rugby union players' attitudes towards wearing protective headgear.
Conclusions: There appears to be a good awareness in UK players that protective headgear is not effective at preventing concussions.
https://pubmed.ncbi.nlm.nih.gov/33607666/
Conclusions: Wearing headgear was not associated with lower odds of concussions or a reduced number of days' absence following a concussion.
https://pubmed.ncbi.nlm.nih.gov/34949511/
Conclusions: Headgear use was not associated with reduced risk of suspected sports-related concussion, non-sports-related concussion head injury or injuries to other body regions.
Of course, there's always one, who sees that evidence, and then insists that scrum caps be encouraged, and rubbishes the research because it doesn't fit his preconception.
. I used to have the same 'debate' with the few backs I coached who wore scrum caps.