Sadly, Jamie Cudmore knows about concussions all too well.
The 38-year-old lock forward from Squamish, B.C., arguably Canada's most famous rugby export over the past decade, has painful first-hand experience. At 6 foot 5 and 255 pounds, the teak-hard Cudmore plays a physical game and has paid the price.
Now Cudmore is looking to help protect others via his soon-to-be-launched Rugby Safety Network, a non-profit foundation he is establishing with wife Jennifer March-Cudmore.
He believe France, where he has played professionally since 2004, is behind North America and Britain when it comes to sports head injuries.
"In France, there's definitely a huge gap in terms of how they're treated, the kind of stigma around them," Cudmore said in an interview. "That's basically where our foundation is going to be headed, in really trying to educate young players around the dangers [of concussions] and basically just how to deal with them properly."
For Cudmore, the answer is simple. Any player suspected of a head injury should not be allowed to play on. Currently if the player passes a head injury assessment, he is allowed to continue.
Cudmore, who moved to Oyonnax this season after more than a decade with high-flying Clermont Auvergne, is not sure how many concussions he has had.
"Counting over the years of ski racing, boxing and pro rugby, there's definitely a few," he said.
"I think every time I was concussed in ski racing and definitely playing sports in Canada, I was always well taken care of. The problem was playing professional sports here in France; I was allowed to continue to play on, and that's where the real danger lies."
Cudmore points to two weeks in 2015, playing for Clermont in the semi-final and final of the high-profile European Cup.
In the April 18 semi-final, Cudmore rammed into 278-pound Saracens forward Billy Vunipola in a head-on-head collision at a ruck. Cut on the forehead, he left the field in the 23rd minute as a blood substitution and was instructed he was done for the day.
Cudmore said he was told several minutes later that he was needed back on the field because his second-row partner was in trouble.
"I went back out there and finished the game and I don't really remember much from the rest of the game."
Before the May 2 final, Cudmore was allowed to rest and saw a neurosurgeon before eventually being cleared to resume playing.
"I ended up playing two weeks later in the final thinking that everything was okay. But obviously it wasn't because I had two more incidents."
Some 10 minutes into the championship game against Toulon, Cudmore slammed into 234-pound New Zealand forward Chris Masoe while trying to make a tackle. Taken off for a head-injury assessment, he was cleared and returned to the field in the 17th minute. In the 58th minute, he came off on another blood substitution after another collision. While he was being stitched up in the dressing room, he started vomiting. Still, he was cleared to finish the game, returning in the 66th minute.
The consequences were painful. He endured a week during which he couldn't sleep. And there were other concussion-related symptoms over several months.
"Headaches, disorientation. I could never remember what I was supposed to do day to day," he told The Canadian Press in a 2015 interview. "I'd have to have a list of everything written down so I didn't forget stuff. It was pretty tough.
Fortunately Cudmore came out of it. "I was lucky just to get cleared to live everyday life."
Several months later he represented Canada at his fourth Rugby World Cup.
The issue of concussions in rugby has come under the spotlight again after a Dec. 3 English Premiership game that saw Northampton Saints star back George North allowed to return after undergoing a head injury assessment after landing on his head following an aerial collision. Northampton later acknowledged North should have not have come back into the game, explaining that its medical team did not have access to TV footage that showed the player apparently being knocked out.
A review panel, set up by Premiership Rugby and England's Rugby Football Union, subsequently issued nine guidelines but no sanctions.
World Rugby, which continues to look for ways to both limit head injuries and improve the concussion protocol, has asked the Rugby Football Union for an explanation on why there were no sanctions.
For Cudmore, the North incident is yet more proof that more is needed to protect players.
"At the professional level, there's a real grey area around how to interpret the different nuances of the law."
He also points to his own experience, saying players must be allowed the proper time to recover.
On the plus side, Cudmore says he has no more concussion-related issues and that his new club, Oyonnax, adheres strictly to concussion protocols.
"I've already seen on numerous occasions that they've erred on the side of caution with other players and it's great to see."