Something is missing from Olympics boxing this year. Did you notice? It’s lot easier to see the faces of male boxers—taunting, grimacing, or smiling in all their Olympian glory. This year, the Olympics ditched boxing headgear for the first time since 1984, making it look a lot more like professional boxing.

The decision, according to statements from amateur boxing’s governing organization—the International Boxing Association, or AIBA—came down to safety. Counterintuitively, referees had to stop matches for head injuries (aka likely concussions) more often when boxers were wearing headgear, according to an AIBA study. But whether ditching headgear actually makes boxers safer—especially from non-concussion injuries—is, well, more complicated.

“This rule change was rather surprising for lot of people. There’s still lot of research that needs to be done,” says Cynthia Bir, a University of Southern California biomechanics researcher who has evaluated boxing equipment for USA Boxing. In fact, female Olympians will still be wearing headgear in boxing, due to lack of safety data. (AIBA did not respond to requests for comment.)

What almost everyone can agree on is that foam padding does little to protect against concussions and knockout blows. Punch hard enough, and you overwhelm the foam’s ability to absorb energy. “The headgear becomes less useful and then not useful,” says Blaine Hoshizaki, a head injury researcher at the University of Ottawa.

Plus, the headgear still leaves boxers vulnerable to punches to the jaw, which are most likely to cause concussions because they whip the head around. “Boxers know that to get the knockout, you need to make the head spin,” says Bir. “Jabs aren’t going to do much.” Your brain normally sits suspended in fluid; when your head whips around, the brain whips around too, the tissue stretching and compressing. This causes concussions.

London 2012: Roberto Cammarelle of Italy (in red) vs. Anthony Joshua of Great Britain (in blue) during the gold medal Super-Heavyweight (+91kg) Olympic boxing final. Jack GUEZ/AFP/Getty Images

But why would wearing headgear increase the rate of likely concussions? The AIBA’s study has a few theories: Headgear makes it tougher to see, so boxers can’t dodge as well. Or perhaps headgear creates a false sense of safety and boxers take more risks. It also makes the boxer’s head a bigger target.

Another matter to consider though: Concussions aren’t the only head injuries boxers get. “A lot of the long-term consequences of repetitive head trauma may be from many, many subconcussive blows over time,” says Charles Bernick, a neurologist at the Cleveland Clinic. Bernick has been following a group of professional boxers and MMA fighters since 2011, and he’s found that even the brains of fighters who have not reported concussions exhibit damage visible in MRI scans.

These subconcussive blows, which don’t have any immediately obvious symptoms, could also lead to chronic traumatic encephalopathy, or CTE, over time. “With concussions, you can see it and you can diagnose it,” says Hoshizaki. “The challenge is the ones you don’t see, don’t feel. This is I think the scary part.” Headgear could mitigate some of these blows. But it’s hard to study because it’s hard to measure how much brain damage these subconcussive blows actually cause; the same punch might cause damage in one person but not another because of the structure of their head or neck musculature.

The AIBA has tried to get more professional in recent years—the extra “A” in the acronym is a remnant from when it had “amateur” in its name. And the group made other changes for the Olympics this year: It changed the scoring system to bring it in line with the pro boxing and allowed professionals to qualify for the games. (Though only three are competing in Rio.) However unsettled the science of boxing headgear may be, pros have a good reason to not use headgear. “They’re trying to promote their brand,” says Bir. “Their face is their brand.”