In part one of this series, Newshub looked at the toll elite sport takes on its players, with many facing a future of diminished mobility and mental health issues.
In part two, we look at two professional athletes forced to retire due to their injuries. Both struggled with their mental health in the aftermath - but managed to find a new purpose.
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Steve Gurney's story
Steve Gurney was one of New Zealand's most successful athletes. He quit his job to train and compete in multisport, winning the Coast to Coast a record nine times and representing New Zealand twice.
"At that stage, I didn't think about what would come after sport," he tells Newshub.
"I was naive and extremely passionate.
"I had 20 years of purpose, and that was to win, to dominate my sport and to earn income."
Halfway through his career, he was poisoned by bat dung while competing in the Borneo jungles and nearly died. Hospitalised with kidney failure, doctors told him he would have to give up racing.
"I ended up quite depressed, but I ignored the doctor's recommendations and got into sport, and ended up winning even more," he says. "I had another 10 years of being even more prolific - more motivated, more driven.
"But I didn't learn the lesson, because in 1996, I had to retire with an injury - torn cartilage in my ankle. I had surgery, but I couldn't compete at a top level.
'I really hit rock bottom'
"That was when I really truly truly hit rock-bottom in terms of depression - I was suicidal. I went to see doctors and they wanted to put me on antidepressants."
Gurney says many athletes have their careers cut short by injury. This sometimes leads to a downward spiral.
"My observation is, for most athletes, it's involuntary. They get injured or they get dropped from the team.
"They live and hope they'll be able to compete for decades. Then, some young better player comes through."
The loss of a sporting career doesn't just lead to a loss of income - for many athletes, it also means a loss of social contacts and a loss of purpose.
"Successful athletes are driven to prove themselves for some reason, and that causes problems when you stop winning or have to retire from sport," Gurney says.
"The biggest thing is depression and the biggest extreme of depression is suicide. Most professional athletes are strong-minded people.
"You don't hear about many suicides, but you hear about a lot who are in a bad place."
Gurney says much of his drive to win was caused by self-esteem issues. He spent years reading books, soul searching and doing spirituality courses to understand what was going through his mind, so he could help himself.
'Don't rely on wins to be happy'
He's now built a career as a motivational speaker and author, sharing his story to help others. While he still cycles and kayaks, he says he's learning not to race.
"Athletes like me are always living in the future," he says. "I would always think I'll be happy once I've won 'x' amount of races - then I won 'x' amount of races and I wasn't happy.
"I thought I was climbing the lofty ladder of success, and I got off and it was a hamster wheel."
His advice to other athletes is to understand what drives you and find another passion for when their sporting career stops.
"Don't rely on wins to be happy." he says. "You cannot rely on your success in sport to be happy.
"The meaning to the answers of life comes from your heart and your soul, not your sport."
Israel Dagg's story
Former All Black star Israel Dagg says he almost decided to quit after he missed selection for the 2015 World Cup.
"I was down, I hated rugby. I was walking down the street and I would look at people and think to myself, 'He's looking at me going 'you're a pussy' and 'you're so useless'.
"I was like, 'Nah I shouldn't be feeling like this'."
After returning to play rugby in the Hawke's Bay, he struggled with a serious shoulder injury.
"I've had moments when I've cried to my best mates and I've cried to my wife, and there's some people out there that might think I'm a pussy and weak, but I don't care," Dagg says on the All Blacks Podcast.
"People cry and need to share their emotions. Everyone has their vulnerabilities and moments."
After receiving help from his friends and family for his mental health, he returned to the Crusaders and the All Blacks, but injuries would again take their toll.
"I hurt my knee in the 2017 pre-season against the Hurricanes in Waverley, when I stood in a pothole on the field and hyperextended my knee. It was a downward spiral from there.
"Three weeks later, against the Reds, I did my PCL and had a meniscus tear," he wrote in an open letter posted to the New Zealand Rugby Players Association Facebook page.
Despite rehabilitation, his knee had been injured to the point it was "bone on bone with no cartilage". Knowing he wouldn't make the All Blacks again, he decided to go overseas.
"I knew my knee was sore, but thought it would be okay and I really wanted the experience of playing overseas, so I headed to Canon in Japan," he wrote in his open letter. "I played a few games and in my final game, it was so sore, I couldn't even kick the ball.
"My knee was unbearable. I was in a deep black hole after that game.
"There was nothing they could do to get me back on the field pain-free, so that made my decision for me. It was time to retire from the game I loved."
- All Blacks: Israel Dagg announces retirement from rugby
- All Blacks: Israel Dagg looks towards life after rugby after announcing retirement
'I was in a deep black hole'
But the end of his sporting career left him struggling and depressed again.
"I really needed to be home and around my family, as I wasn't in a good headspace," he wrote. "I really struggled over summer, because I didn't know what was going to happen.
"I was a big, lazy, sad sack and as we know when you are mentally struggling, you need to be exercising and connecting, but it was a battle."
Fortunately, the Crusaders provided him with a role helping other players, which gave him a purpose and made his headspace better.
'Make the most of it'
And he has advice for other players who will end up in the same situation he's in.
"Rugby is cut-throat and when you are done, someone else comes along and takes your place," he wrote.
"The transition will never be easy, but knowing you have things behind you, like your house and your investments, makes the transition easier.
"This is why I try and tell the lads to make the most of it, because when it is over, it is over. You have a great opportunity to gain tools and meets some great people, so make the most of it."