It was not the experience of getting knocked out cold that persuaded Kat Merchant to abandon her dreams of playing professional rugby. Her family certainly feared the worst as they watched her crumple to the turf and start to convulse after a collision during a club game for Worcester against Saracens in late 2013.
She had endured concussions before -- at least nine of them, some of which left her unable to train for months at a time or even perform work that required looking at a computer screen. But none of those previous injuries, in isolation, had appeared quite so brutal. Afterward, Merchant was asked whether she would ever play again.
"We're four months out from World Cup training," she replied. "So, yeah, that's my aim."
Women's rugby in England, at that time, was an amateur pursuit. Members of the national team received a stipend to cover loss of earnings during the tournaments and training camps, but that was all. Merchant had lined up a professional contract to play rugby sevens -- a seven-a-side variant of the sport -- later in 2014, yet it was the shot at a world title that mattered more.
She grabbed it with both hands, helping England become champion for the first time in 20 years. By the time the confetti had settled, however, Merchant, then age 28, knew she would never play again. During England's opening game, a 65-3 rout of Samoa, she had suffered another head injury.
"It was really innocuous," she recalls. "Somebody in a ruck just brushed past me and it made me -- not see stars, but all my decision-making became slower.
"If I run full-pelt into somebody and we're both sprinting and my head hits their hip, you can understand, 'OK, that's high impact.' But if it starts to become not high-impact situations any more, just the little knocks you're going to get every day, that to me says you're looking at long-term problems."
'Tired and lazy arguments'
Ever since American football began to wrestle seriously with its concussion problem, there have been suggestions that it could learn from rugby. From the outside, it was easy to look across and see another collision sport that somehow appeared safer. The absence of helmets led rugby players to tackle with their shoulders and arms instead of putting their heads into danger.
In the same year that Merchant helped England to a World Cup win, the Seattle Seahawks released a teaching video, voiced by head coach Pete Carroll, promoting their "Hawk Tackle" technique.
"How we teach this system of tackling was recently inspired by those who play rugby around the world," Carroll says during the introduction. "Rugby players have taken the head out of the game and truly exemplified shoulder tackling. You'll see several clips of rugby tackling throughout the film."
The video drew praise from NFL commissioner Roger Goodell, who encouraged "players, coaches and parents at all levels of the game take the time to watch it."
The assumption that rugby had a better handle on concussions than football, however, might have been flawed from the get-go. The most recent injury audit performed by England's Rugby Football Union (RFU) established that concussions in elite-level professional games were occurring at a rate of 13.4 per 1,000 player hours. On those numbers, you would expect to see a concussion slightly more often than once in every two games.
There were 182 reported concussions in the NFL's 256 regular season games in 2015 -- a higher rate, but hardly by a drastic margin. In both sports, the figures have risen sharply in line with growing awareness. The RFU's audit shows that rugby's rate of identified concussions has doubled in the past two years alone.
Until those figures stabilize, it will be easy to believe that they underrepresent the scale of the issue. Dr. Willie Stewart, consultant neuropathologist at the University of Glasgow and a member of World Rugby's independent concussion advisory panel, says any claim that rugby players experience a lower risk of brain injury than football players is essentially unproven.
But the most significant development in rugby's management of head injuries might be just around the corner. World Rugby is expected to publish the initial results this week from a detailed analysis of 600 incidents leading to head injuries during elite games, with the aim of establishing precisely where and how these took place.
"When we actually look at head impact numbers -- and these are head impacts rather than concussions -- people playing rugby are exposed to as many, if not more, head impacts as they are in American football of similar forces, if not higher." Dr. Willie Stewart, a member of World Rugby's independent concussion advisory panel
"To say that American footballers lead with their head and that therefore is the problem would be the same lazy argument as once said, 'Only boxers experience brain injury in sport,'" Stewart contends. "These are just tired and lazy arguments that people put out within sport to try and deflect attention from the injury.
"When we actually look at head impact numbers -- and these are head impacts rather than concussions -- people playing rugby are exposed to as many, if not more, head impacts as they are in American football of similar forces, if not higher."
What rugby can teach
If rugby is not inherently safer than football, then are there other ways in which it has set a positive standard to follow?
Certainly World Rugby's grassroots awareness campaigns around concussion are laudable. Extensive resources explaining how to identify and manage head injuries are available on the governing body's website, translated into eight different languages.
Crucially, the message has been kept simple, with advice boiled down to six R's -- Recognize, Remove, Refer, Rest, Recover, Return -- that all reinforce the same message: Any player showing any signs of a concussion in an amateur game ought to be removed immediately and taken to a medical professional.
However, simply putting such information on a website hardly guarantees that everybody will digest it, and rugby faces challenges that football does not in the sheer diversity of its participants. World Rugby's website boasts of 6.6 million people playing the sport across 120 countries.
But there are at least some suggestions that this guidance is having an impact. The number of catastrophic injuries suffered by people playing rugby in South Africa has fallen precipitously, with 21 acute spinal cord or head injuries -- including one death -- suffered across youth and club rugby in 2007, compared with a total of four last year.
This shift owes much to local initiatives, and most notably the BokSmart program, which obliges all coaches and referees to undergo mandatory education and certification every two years to ensure that their knowledge of issues, including concussions, is up to date. The program models its information on that supplied by World Rugby.
At the elite level, there is more debate over rugby's approach. Current regulations allow for any player suspected of suffering a concussion to be taken off the field for a 10-minute sideline assessment by an independent medical practitioner, who can then decide whether the player can return.
When the principle was first introduced in 2012, in a slightly different form, it caused one of World Rugby's medical advisers to resign in protest. The sport's previous guidance had stated that any player suspected of a concussion should simply be withdrawn and kept out for at least a week. Dr. Barry O'Driscoll could not abide what he perceived as a softening in this approach.
The rule's defenders take a different view -- arguing that without this pitch-side assessment, most concussed players simply never left the game. According to Dr. Simon Kemp, head of sports medicine at the RFU, "Average assessment for a player with a head injury at the 2011 World Cup was done on the field and lasted 64 seconds." World Rugby cites figures from a 2014 study showing that the percentage of players returning to the field with a concussion had fallen from 56 to 12 percent since sideline assessment was introduced.
Professional rugby clubs themselves are also taking a lead. During the past 18 months, players on Saracens' men's team have worn impact sensor patches, designed by Seattle-based tech company X2 Biosystems, behind their ears during games to monitor the force of all blows that they suffer to the head. This season the team, in conjunction with University College London, has also been collecting and analyzing blood samples from players to detect for biomarkers associated with brain injury.
The hope is that such studies might reveal ways in which rugby could adapt to reduce the risk of brain injury, while maintaining, as Dr. Kemp phrases it, "the essential characteristics of the game."
Not everyone believes that to be possible. This past March, a group of more than 70 doctors and health experts in the United Kingdom submitted an open letter to parliament calling for tackling to be removed altogether from school rugby. The Department of Education responded with a statement saying it had no plans to do so.
This campaign has no support from the former players and doctors interviewed for this story. Even those who have criticized World Rugby's handling of head injuries, such as Dr. O'Driscoll, still insist that the game brings more good than bad.
That's a view that Merchant would echo. Two years after her retirement, she still feels some adverse effects from her injuries, occasionally mixing up her words or experiencing bouts of fatigue. But she does not know if she would have done things any differently.
"It's difficult, because, like anything, you never think it's going to happen to you," she said. "I was aware of people saying, 'Oh, I'm not sure how many concussions you should have,' and I would say, 'It doesn't matter, it doesn't matter.' Because to me, the most important thing in the world was winning the World Cup. You just don't really stop to think, 'Oh, what will I be like when I'm 60?'"