La Trobe University Professor Alan Pearce said players could develop deadly brain disease after repeated concussions.

"We've known about this issue for nearly 100 years," he said.

Professor Pearce said adults were free to choose sports that risk head trauma.

But the growing brains of child and teen athletes should be protected and not exposed to concussion, he said.

"We have a duty of care to the next generation of AFL, rugby and soccer players," he said.

Players returning to the field after a head trauma risked more injuries, the concussion researcher said.

Concussed brains were more likely to stumble, fumble or misjudge, Professor Pearce said.

He said the risk a player would injure themselves increased by 2.5 times once they had been concussed.

"A player's brain isn't processing as efficiently as it could," he said.

The long-term dangers of repeated head traumas were more insidious.

"Later in life, we see evidence of cognitive impairment after more than three concussions," he said.

There was also a risk of developing neuro-degenerative diseases like Parkinson's disease and motor neuron disease, he said.

Dementia risks increased three to five times, he said.

"It doesn't matter if you wear a helmet or any other padding, the force being transmitted into the brain tissue is enough to do damage," Professor Pearce said.

"We know that if you get enough of those impacts, it will create damage that's irreversible."

"The whole notion of combat sports, like boxing, is to give your opponent a brain injury," Professor Pearce said.

"That's the scary thing about it," he said.

In 2015, the Australian Medical Association (AMA) called for a ban on combat sports for people under 18 years.

Professor Pearce said the AMA wanted boxing banned because of the high risks of head trauma.

But the same doctors weren't campaigning for change when football players sustained multiple concussions, he said.

The AMA was contacted for comment and referred ACM to press releases confirming these positions.

"We need to have biomarkers when someone is suspected of having a concussion and better ways of detecting the injury," he said.

"We also need to increase rigour and have more science involved in the conversation," he said.

Australia's Concussion Legacy Foundation are advocating to modify contact sports for kids younger than 14 years.

The "tag" rugby variation reduces risks of injury to their growing brains, where Velcro tags stuck to the player's waist are snatched in place of tackling.

Kids could still learn the skills of the game, like kicking, passing, handballing and marking, Professor Pearce said.

"But without the repetitive impacts to the brain," he said.

Professor Pearce said contact sports should follow tennis' lead and use lower nets and smaller rackets to help kids sidestep the extra strain on their bodies.

Modifications like this reduce injuries and keeps kids in the sport, while not reducing their resilience, he said.

They differ between codes, but professional clubs had rules and guidelines that dictated an appropriate recovery time from a concussion, Professor Pearce said.

Junior and club level teams weren't necessarily associated with the ruling bodies of the sport. So those rules and guidelines weren't enforced, he said.

"For example, AFL is too big to police what happens at all the levels of the game, there's a lot said about 'athlete safety being the highest priority,'" he said.

"But club and junior levels aren't monitored, they're not part of the league."

To set an example for the next generation, high profile players should let their bodies recover properly before coming back to the field, Professor Pearce said.

The "warrior" culture of Australian contact sports can encourage players back on the field before they're medically safe to rejoin the fray.

Halley Derera played professional Rugby Union in Australia and England and said concussed players often rushed back on the field, driven by their competitive spirit.

"It's the mentality of an elite athlete, you always want to be better," she said.

"Players want to play and it can be easy to push past a headache - because it's not tangible," Ms Derera said.

"But it's scary to think about the long-term ramifications of too many concussions," she said.

Sometimes, players needed to be protected from themselves, Professor Pearce said.

Concussions should be taken seriously and athletes should not be allowed to continue playing if there was any concern they may have sustained a bad hit, he said.

Athletes were trained to "run through walls, not show pain, commit to your team mates and spark fear in the opposition," he said.

"All of a sudden we're asking you to admit that you've got a headache," he said.

IN OTHER NEWS:

Professor Pearce said head injuries happened during training as well as in matches.

The UK Rugby Federation introduced limits on tackle drills in team training to combat this.

Players could practice collision or tackling based training drills for a maximum of 15 minutes of per week.

"It makes coaching staff think about how to train these athletes smarter, instead of harder," Professor Pearce said.

The focus has shifted to training strategies and skills instead, and the outcomes have been positive, he said.

"These teams go into matches fresher and tend to perform better in win-loss ratios," Professor Pearce said.

"Traditional forms of training are so ingrained, it's hard to imagine another solution."

The NRL and AFL were contacted for comment but had not responded by presstime.