MMA is a tricky one. A fight can get bloody, but because of the light weight gloves (and kicks), any single good blow typically ends the fight. Fights can also end by submission without having to knock someone out. A professional UFC fighter, and a professional NFL player would be an interesting comparison.
What about the board sports (wake/snow/skate)?
I doubt they're anywhere near the others. Boxers and football players get hit every match as a matter of course. The whole point is to hit people.
Board sports, on the other hand, the entire point is not to fall down or run into things. A person can snowboard an entire lifetime and never take as many hits to the head as boxer gets in a single match.
The science on football vs. MMA is murky, and I don't know if a definitive ranking can be established, but aparently it's more common to play through a mild concussive event in football, according to a current MMA fighter & former footbal player when asked which sport was more harmful: "It's football," Saint Preux said. "Obviously anytime you get knocked out, you get a concussion. You get hurt, your bell gets rung, that's a concussion. What usually happens is you play through it. Week 1, you get a minor concussion, you keep going. Week 5 comes around, it's worse." [2]
I would expect that overall the board sports are safer, but that when injuries do occur they tend to be more serious. For instance, I normally don't suffer any injury at all when skiing, and the worst injury I have ever received from skiing is a sprained ankle. However, I don't consider skiing a 'safe' activity, since the consequences of a mistake could easily be as serious as having an accident on my motorcycle, such as hitting a tree or other solid obstacle. But I don't routinely expect to be injured when I ski, while a fighter or football player can reasonably expect at least some injuries every time they play (and oftentimes even practice). I would actually expect that overall sports like non-US football and basketball would carry higher risk of injury than skiing/snowboarding. Skateboarding is interesting, I was friends w/ a group of fairly serious skaters, and aside from superficial injury (road rash, etc) it seemed paradoxically fairly safe (anecdotally, it seemed more common for someone to sprain an ankle playing pickup basketball) and hitting your head was an extremely rare event.
I can't find a link to the full study (this page is focused on the relative safety of shooting sports), but according to [3], the ranking on injuries/100 participants is:
Football > Ice Hockey > Soccer > Basketball > Baseball > Running/Jogging > Skateboarding > Gymnastics
Ice skating is fairly low (0.7/100), and skiing isn't listed, but I would expect it to be higher. Fighting also isn't listed, but I would think it would fall between hockey and soccer.
[1] https://www.fightersonlymag.com/features/boxing-vs-mma-safer...
[2] https://bleacherreport.com/articles/2830774-football-vs-mma-...
Another interesting sport to compare would be hockey. While hockey players don't tackle each other like football players do, they do check each other into the boards and those can be some big hits. Is CTE prevalent in professional hockey players as well?
Somewhat surprising, soccer also has huge concussion issues, so probably CTE as well. They'll try and argue no proven linkage, but to me that doesn't make sense.
My 10 yr old plays football and lacrosse, but next year we will probably switch him to flag football and basketball exclusively. It's just not worth the risks.
Every venue will require its leagues/teams playing on it to get insurance. And if nobody will underwrite that insurance, or the price is sky-high, then the sport practically won’t exist at the recreational or professional level.
Doubly so if governments start refusing to subsidize the construction of their rec/professional playing areas.
Humans are not rational brains riding round in a sort of meat carriage, we are animals and our whole body (and social setting) adds up to who we are. Physical conflict is part of human life - specifically a proportion of young men are predisposed to physical rivalry. Taking options to express this away does not remove the predisposition, it merely shifts it to other outlets which may be much less constrained and much less positive.
Behavioral issues in young males without a physical outlet for aggression?
I'm not sure what type of childhood you had, but the idea the soccer and high school football is going to give a person brain damage is goofy simply based on the current and available data.
If you simply look at that massive number of males that played high school football in, for example, the 1970s, we would have epidemic levels of serious brain issues in an enormous percentage of the the male population. We would be talking about 10s of millions of people with serious brain damage. For example, in 2016, over 1,000,000 young males played high school football. I think it is safe to say that men between 50 and 60 years old do not all have serious brain issues. Even though a very high percentage of those men played high school football.
With that said, we have much lower numbers of men that have played division 1 college football and an even smaller number that played more than a few years in the NFL. In the NFL, the average career length is only 3 years. The speed, size, and strength increases dramatically at that level and we are seeing data that could indicate real issues with brain injury.
It is strange to see people on a site like HN that do not even have a basic understanding of data driven concusions.
How would we know? Could it be possible that irrational support for extremists is a result of CTE?
There are so many other sports though. Soccer can be played without heading (Barcelona under Pep Guardiola were acclaimed for playing it that way), and there's flag football, basketball, field and ice hockey, lacrosse, wrestling, karate, judo, handball, ultimate Frisbee.