The way players train need to be addressed "very quickly", says the head of the Rugby Players' Association, after ex-professionals said the sport has given them permanent brain damage.

All eight have been diagnosed with the early signs of dementia and blame repeated blows to the head.

"It's been very distressing for everyone," said Damian Hopley.

Hopley, the RPA's chief executive, told BBC Sport more education was needed, in addition to greater refereeing consistency, a high tackle sanction framework and a reduction of contact training.

"A big percentage of injuries occur during training so I think that has to be part of the opportunity to address these things and look at what can we do to make the game safer, as has been talked about," he said.

"Perhaps training protocols is something we need to address very quickly."

All eight players to have come forward so far have been diagnosed by neurologists at King's College London with early onset dementia and probable Chronic Traumatic Encephalopathy (CTE).

CTE can develop when the brain is subjected to numerous small blows or rapid movements - sometimes known as sub-concussions - and is associated with symptoms such as memory loss, depression and progressive dementia.

Lawyers for the group suggest another 80 former players between the ages of 25 and 55 are showing symptoms and have serious concerns.

Global governing body World Rugby told BBC Sport: "While not commenting on speculation, World Rugby takes player safety very seriously and implements injury-prevention strategies based on the latest available knowledge, research and evidence."

The Rugby Football Union (RFU), which runs the sport in England, said: "The RFU has had no legal approach on this matter. The Union takes player safety very seriously and implements injury prevention and injury treatment strategies based on the latest research and evidence.

"The Union has played an instrumental role in establishing injury surveillance, concussion education and assessment, collaborating on research as well as supporting law changes and law application to ensure proactive management of player welfare."

Former Northampton Saints lock and now RPA player liaison officer Christian Day said the accounts from Thompson and former Wales international Alix Popham have been "harrowing" and that "as a recent former player, with a young family, it hits home".

He told BBC Sport he had "seven or eight" concussions during his career but believes players look out for each other more now and more gravity is given to head injuries.

"You can never sit still," he said. "I do think some amazing work has been done, I do think that the game has changed a huge amount particularly in terms of education and players' awareness and also the testing that is done. But that doesn't mean we should stop here."

"The regulation of contact training is something that we have pushed for and brought up in recent years and it's probably something that we need to look at seriously now, as concussions happen in training and training is a controllable environment.

"We surveyed our membership around 12 or 18 months ago now and one of the most polarising questions was around contact training, and our membership were pretty united on that front, in terms of further regulation of that is important.

"I think it is very tribal, different coaches will have different methodologies and some players will say 'our level of contact training is absolutely fine' but at other clubs players will feel they do too much. It's a controllable environment so we shouldn't have so many injuries in training."