Players from the Saracens rugby club are taking part in a research project that could have a bruising impact on their sport and others with high levels of physical contact.
Scientists will be studying the Hertfordshire "men in black", currently top of the rugby union premier league, in search of biomarkers that indicate a risk of long-term brain damage.
If the molecules are found they could form the basis of a test to identify individuals who need help even if they appear healthy - bringing in to question their fitness to play.
The research could also lead to major changes in the rules of rugby and other sports, reducing the risk of head injury.
It is part of a worldwide investigation into a still little-understood condition called chronic traumatic encephalopathy (CTE) that is thought to arise from blows to the head.
The disorder is marked by long-term, progressive brain damage leading to Alzheimer's-like symptoms of confusion and dementia that may only surface years after the initial trauma.
"Concussion", a new movie starring Will Smith and Alec Baldwin to be screened in the UK next week, tells the true story of how CTE was first identified in former American football players despite attempts to suppress the discovery.
Clinical neuroscientist Professor Huw Morris, from University College London, who is co-leading the Saracens research, said: "What we're doing is taking biosamples from players. They're donating blood, urine and saliva samples at the start of the season, and then we're following players up.
"We'll be able to build up a biochemical profile of what happens to people during normal rugby games, when they're getting muscle impacts and so forth, but also to people having head injuries during games."
He added: "The aim is to have something that is an adjunct to a medical test."
Players would also wear accelerometer "patches" to measure the forces on their bodies, and video footage of games would be analysed to spot potentially dangerous moves.
The ultimate goal was to find a way to identify at-risk individuals and guide rule changes that make aggressive contact sports such as rugby safer, said Prof Morris.
Currently there is no way of telling when athletes who have not been knocked out or shown symptoms of dizziness, nausea and memory loss might be likely to suffer long-term brain damage.
Many ex-boxers once dismissed as "punch drunk" as a result of repeated blows they received in the ring are believed to be suffering from CTE.
News of the research comes on the eve of the Six Nations rugby tournament which kicks off this weekend.
A year ago the sport was rocked by controversy after Welsh winger George North was twice knocked unconscious in his side's opening match against England, but allowed to keep playing.
Partly as a result of the American research focusing on the National Football League, there has already been a "sea change" in attitudes to contact sports, said Prof Morris, whose two sons play rugby.
"Ten or 15 years ago people wanted to minimise the situation," he said. "They might have received a knock or bang on the head, but decided it was nothing and got back on the pitch. Now people are aware that it's not the most sensible thing to do."
Colleague Professor John Hardy, a neuroscientist at University College London, stressed that the researchers had no wish to be spoil-sports.
He said: "None of us wants to prevent people playing sport. The last thing we want is for everyone to become couch potatoes who develop Type 2 diabetes, get fat and die early.
"We want people to enjoy sports, but as safely as we can advise them."
Research on Alzheimer's had shown how a localised brain injury can cause damage that slowly spreads down neural pathways, he said.
The Saracens study is supported by the Drake Foundation, a non-profit organisation dedicated to improving understanding of concussion in sport.