And she admits that it doesn't get any less stressful to watch her partner in action: "I get a yellow spike during the Classics on my Whoop, which means my stress levels are high," Bertels laughs. "Everything has to be right then, and you want him to be at his very best. It automatically puts a bit of pressure on me too: he has to train well, eat well, sleep well."
A chance encounter
Bertels is the daughter of Belgian water skier and powerboat racer Danny Bertels, and met Van der Poel in Finland in 2018. She was there organising a work trip for Porsche Centre Antwerp.
"I didn't really know who he was. I knew he was a cyclist, but I had no idea about the cycling world at all. But I think it was good to start with a clean slate, without having any opinion of him."
The eight-time cyclo-cross world champion's influence has helped Bertels to build a more healthy relationship with sport over the years, even though she isn't nearly as competitive as Van der Poel.
"I wish I was as driven as he is. He gives everything for everything in life. I give up more quickly, and I wish that wasn't the case. I find it more stressful when I have to exercise with others, and I wish it were different."
Can be hard to keep up
The relationship has undoubtedly transformed her: "The 33-year-old Roxanne would always beat the 25-year-old Roxanne, at everything."
That includes cycling: a hobby she's only picked up recently towards the end of last year: "I said I'd never love cycling, but I take that back. I sort of drifted into it, because I'd picked up a minor hip injury in August. The doctor said I'd better not run for a bit, so I thought I'd give it a try. My first ride wasn't much fun, but after that it was actually pretty cool."
While riding her bike, or indulging in other sport activities, she can always rely on Van der Poel's word of advice: "Mathieu has a really good outlook on what's good for you when it comes to sport. He always gives me good advice, whether it's about running or anything else to do with health."