From pizzas and cheeseburgers to gluten-free and low carb diet, tennis players want that little edge over competition.
Christian Filhol is a 53-year-old Frenchman with a faded yellow sunhat and a straggly grey beard.
At any of the four Grand Slams, one will find a tired looking rental car parked by the side of the road. This is where Filhol has slept every night during the premier tournaments for the last 23 years.
He has worked with most of WTA Tour’s leading players over the past three decades. The formidable list includes Justine Henin, Mary Pierce, Li Na, Daniela Hantuchova, Elena Dementieva, Cara Black and Sania Mirza.
On grunting : “It’s important for players to find a way to show the intensity of their focus and determination. Grunting is a way of doing that.”
The best forehand : “I believe Sania Mirza’s forehand is one of the best shots on tour. It has power, disguise and accuracy. Even the male players in mixed doubles don’t like it.”
Doing interviews : “Some coaches always seek the limelight. I don’t. I prefer to stay in the shade.”
Filhol does few interviews (he says this is just his third in 20 years) but when he does open up, he talks often of freedom.
Freedom is central to his life and his way of working. Valued as a consultant on technical and mental aspects of the game, the Chinese federation hired him during the Olympics and the Fed Cup.
They have repeatedly offered him a permanent role but Filhol has declined.
“I like the freedom to try and help as many players as I can to achieve what they want to achieve,” Filhol told Al Jazeera.
This is the approach that has made Filhol such a valuable resource.
Having worked with hundreds of female players, he possesses an almost-encyclopedic knowledge and a database containing thousands of videos of the world’s best.
This enables him to provide minute technical details on how the players can correct or hide certain flaws in their game.
However, his understanding of how to tap into a player’s potential doesn’t always centre on forehands and backhands.
“A large part of tennis is learning how to beat the opponent within yourself.
“It doesn’t matter whether you have great power like Pierce or you’re tenacious like Black. Body language is hugely important, both to drive yourself and unsettle your opponent.”
But despite his wealth of experience, he dislikes being described as a coach.
“I prefer to be called an advisor. I don’t like the implications of the word coaching. Its meaning derives from the ‘driving of horses’ and there are too many coaches in the game, especially in the juniors, who act like they’re doing this.
“It should be about imparting knowledge so the player can become the master and the one in charge.”
In the current game, most entourages share private apartments or luxury hotels with the player. But Filhol prefers to sleep in the back seat of his car, often to the dismay of his charges.
“I’ve slept in my car for almost 20 years. I do it even when I’m back home. And I love it. I don’t sleep well in a bed these days. My body is used to sleeping in a seat.
“I ask the players I work with to donate the money they would spend on my hotel to a charity. I prefer it this way.”
This nomadic, almost bohemian, lifestyle has landed him with a number of near misses.
He was sleeping in his car near the Twin Towers during the 2001 US Open, just a week before the attacks.
Three years later, he was supposed to be at the beach in Sri Lanka when the tsunami hit. But a late decision to head to a local tennis club to give lessons saved his life.
Filhol started travelling this road in his early 30s when he was working with a group of young French players trying to make it in the tennis world.
In his spare time, he strung rackets to pay the bills. Sleeping in his car was just another way to keep things affordable.
“I’ve always driven from tournament to tournament across Europe, America and Asia. That way, it costs me around $10,000-$20,000 to travel the world each year.
“And I can do some sightseeing at the same time.
“The players I work with these days, I could live a more normal life but I prefer not to spend too much money.”
Filhol has never done things the conventional way. Growing up in Montpellier, he taught himself the game aged 15 before becoming head coach at a local tennis school two years later.
He never intended to coach on the main tour but changed his mind after realising it was the only way to gain serious respect.
“I enjoy coaching beginners the most. I thought I would return to that. But I became frustrated that the players, parents and coaches at my local tennis school wouldn’t listen to me.
“I realised that the only way to get everyone to listen to me was to continue working with the best at the Grand Slams.”
‘I hate contracts’
Elite tennis is an environment often dictated by strict contracts and furious salary negotiations.
But Filhol has endeared himself to players by offering his services with such a liberal approach to compensation that he often works for free.
It may be two decades since he started out on tour but Filhol still spends 48 weeks every year on the road. He has no wife or children.
For some, it may appear a lonely life, but Filhol would not have it any other way.