The challenge of losing weight, the doubts and the 'relief' after his first defeat in almost 10 years, the motivation to train again found during the lockdown.
Teddy Riner's comeback journey has been magisterially documented by the movie 'Teddy', released in France at the end of July
For 19 months the life of the double Olympic judo champion was captured by a camera as he resumed training after a break of one and a half years.
'Teddy' also offered a unique insight into the life of one of the sport's legends.
Here are five things we learned from the film.
1 - He has a psychologist to support him
Riner was the first athlete in judo to create a dedicated team looking after him.
The decision was taken after he controversially lost the final of the open weight class at the 2010 World Championships in Tokyo to Kamikawa Daiki.
The Frenchman didn't want to leave anything to chance - or to a referee's interpretation - any further. So he knew that he had to be surrounded by the best professionals.
At the INSEP (France's National Institute of Sport and Performance) he trains with Yann Morisseau, the coach of the French weightlifting team, and with his personal sparring partner, the German Nico Kanning, who's been paid since 2010 to be thrown without providing too much resistance.
"Nico is my shadow, I owe him as much as to my coaches. He deserves credit for each of my wins." - Teddy Riner
In 2017 he recruited former judoka Laurent Calleja as his personal trainer.
French Judo Federation coach Franck Chambily, his 'Yoda master' and 'second father', is also overseeing his preparation, while the psychologist Meriem Salmi, who's been working with him since he was 14, is key in managing the emotions of the 10-time World champion.
"Even if I try to hide (my feelings), it's pointless because she knows and she feels what's going on," the three-time Olympic medallist said.
2 - He has an 'emotional relationship' with sugar
In November 2018, when he resumed training in Japan, Riner - who's 2.04m tall - weighed 166.6 kg, 20 kg above the ideal.
"I suffered, I (looked) like a tank! When you start coming back, you’re straight into action. I regret all the food excesses I had," he said with a smile as he recalled the struggles during a climb on his bike.
"When you stop for 18 months, you necessarily put some weight on. And when my partner was pregnant, well, there were some moments when I was not particularly careful."
"He's got a true emotional relationship with sugar" - Luthna Plocus, Riner's girlfriend
The Frenchman has always admitted he has a sweet tooth, in particular for French crepes.
"I've loved sugar since I was really young, so it’s quite complicated. When I start wanting to lose weight, I go slowly, you cannot wean me off like that!"
Even in 'Teddy' you can see the 31-year-old indulging in Nutella waffles during breakfast at the hotel.
Fighting with the scale is a leitmotif in the movie:
"Weight is a constant issue for me, because very simply, without taking care of it, I cannot play my best judo, I cannot be dynamic as I have always been in my fights, I cannot start a move and I cannot be that guy with fire in the legs."
3 - He's a playful dad
Since competing at high level, Riner has been used to spending the majority of his time with his team.
But also his 'natural' family plays a central role for him.
His father Moise, his mum Marie-Pierre and his long-time girlfriend Luthna Plocus have been a constant presence during his career and in 'Teddy' they give us the chance to discover a more intimate side of the judoka.
"Teddy has always been like this, he's a kid who likes to play and have fun, sometimes he's very annoying!" - Moise Riner
"It's not simple, it's a life apart," said Luthna when she was asked what it's like living with one France's sporting stars.
"He's not just a high-level athlete. He's a very, very high-level athlete. He's very demanding, especially with himself."
Privately Riner is also an affectionate dad, who loves having fun and is seen playing hide-and-seek with his son Eden in a metro station in Tokyo.
During his 18-month-long break and especially the recent coronavirus lockdown he had more time to spend with his two-year-old daughter Isis.
"Having that break allowed me to breath, spend some time with my grand parents, my family. I am glad I could take some quality time like that for the first time in 14 years," he said during the documentary.
"He's probably the most sensitive person at home" - Luthna Plocus, Riner's girlfriend
4 - Dealing with defeat for the first time in 10 years
Defeat against Japan's Kageura Kokoro at the Paris Grand Slam in February ended a run of 154 straight victories.
Teddy Riner was beaten for the first time after 9 years and five months.
The Guadaloupe-born judoka understood how hard it was to deal with the pressure of winning all the time.
"You have no idea how relieve I feel. It’s so weird as well though." - Teddy Riner talking about his first defeat in almost 10 years
"It’s obvious that you learn more from your defeats, everybody knows that," he admitted.
"I am proud of what I did, but after 10 years [undefeated], it is really heavy on your shoulders.
"And for Tokyo, I really need to have the least possible pressure. So now it’s clearly less weight on my shoulders."
"I need to use this (defeat) to bounce back and draw the strength to win the next competition, take my revenge and focus on my ultimate goal, the Olympics Games in Tokyo" - Teddy Riner to Brut
5 - A new motivation found during the lockdown
"It's been like a break in my life. It allowed me to manage myself in training, because usually my coaches take care of everything. I managed my sessions, my recovery. It's been a time where I rediscovered myself," the judo champion recently told French website Brut.
During the weeks of lockdown, Riner found a new motivation and started to train harder.
He set up a tatami – a judo mat – and a proper gym, with weights and a spinning bike, above his office in Levallois Perret, Paris.
"Surprisingly, I really enjoyed training alone, twice a day," he recalled.
"I lost over 10kg, now I'm 143kg, just 3kg over my ideal weight."
His dad - watching him on a video call from Guadaloupe - was surprised too to see his son working so hard despite the judo season being on hold.
"He's looking for emotions, he needs them to keep going" - Laurent Calleja, Riner's personal trainer
The Frenchman even challenged his followers on social media as he performed burpees and skipped the rope on his rooftop terrace overlooking Paris's iconic Grande Arche de la Défense.
After a long and difficult journey, Riner seems now back on track and the quest for a third consecutive Olympic gold medal can continue.