Former England international James Haskell is among a group of ex-players and coaches demanding World Rugby make urgent reforms to protect players from concussion.
England's 2003 World Cup-winning hooker Steve Thompson is one of a number of former players who are exploring legal action against rugby's governing bodies after being diagnosed with neurological conditions.
In an open letter to World Rugby the newly formed Progressive Rugby lobby group, which also includes referees and medical experts, outlined concerns along with a suggested plan of action.
Signatories include Thompson and former Wales star Alix Popham, who is suffering from probable chronic traumatic encephalopathy (CTE).
Proposals include a limit on contact in training, restricting match substitutions to injured players only - to reduce the incidence of fresh players making high-impact tackles on tired players - and a guaranteed minimum number of days off between seasons.
They would also include a career "health passport" for players and increased education at all levels regarding head injuries and concussion management.
The group says an extension of the minimum number of days before a player is allowed to return following concussion should be set at least three weeks instead of a week.
Haskell, who also signed the open letter, believes more must be done at a faster pace to help learn from the past and protect the next generation.
"I always have concerns that they were very slow moving and that so much of what we do in a team sport was out of fear," said the 35-year-old former backrow forward.
"If you did not beat each other up [in training] on a Tuesday, then you are not prepared for a Saturday - but that is down to mental preparation, so I always wondered why we were doing so much extra training.
"I was always concerned that we are doing things out of fear and never out of science."
Several players missed the second round of Six Nations matches due to knocks to the head in the opening games, including Ireland's Johnny Sexton and James Ryan.
World Rugby issued a statement in response to Progressive Rugby's open letter, stressing "the welfare of the global rugby family is, and has always been" its priority.