The IRONMAN World Championship is set to return to Kona, Hawaii in a week’s time after a three year hiatus following the Covid-19 pandemic. This iconic race, which has taken place since 1978, is one of the only championship events across any sports where amateur athletes have the chance to race side-by-side with the professionals.
Tom Oosterdijk, who qualified for the IRONMAN World Championships three times as an age-grouper, recently finished 12th in the professional field at the European Long Distance Championships at Challenge Almere-Amsterdam.
And the Dutchman, who turned pro in 2021, was kind enough to speak to us about his experiences as an age-grouper in Kona, the transition from amateur to pro and his hopes to come full circle in the future on the Big Island.
From finishing line to starting point
For many age-groupers, the IRONMAN World Championship in Kona, typically held in early October, is a reward for all the hard work put into qualifying for the race, with simply reaching the finishing line on the Big Island a huge achievement in its own right.

For other athletes however, such as Oosterdijk, competing as an amateur on the Big Island is an indicator of what’s possible. Recounting his first experience in Kona, Oosterdijk recalls the sense of awe that comes with “being around the fittest people on earth”, saying: “It is really motivating to be in alongside all the great athletes and all the biggest brands.”
Having only been in the sport for a little less than a year and a half before his first trip to Kona, the impression made on the Dutchman as an age-grouper in Kona was instrumental in his decision to transition from the age-group ranks to the professional field.
The chance to race alongside the professionals, “to speak to them and see the people that I look up to”, is just one of the major features the IRONMAN World Championship offers to amateurs. No other event better embodies the sport of triathlon that Oosterdijk describes as a “small family community”.
Making the change
Whilst qualifying for the age-group world championships is a huge achievement, making the transition from amateur to professional racing is another big step up. For Oosterdijk, the confidence to quit his job in international tax to pursue full-time triathlon came from his results as an amateur.
Talking about his decision to make the change, the co-host of the Triathlon Mockery podcast said: “I realised after racing in New Zealand with Joe [Skipper] that if I had been racing in the professional field, I would have been making prize money.”
And participation in the pro field obviously also offers the chance to race alongside faster competition too.
Following solid performances as an age-grouper, Oosterdijk was given his professional licence by the Dutch Federation in 2021, resigning from his job after deciding that “if I wanted to do it, I needed to go for it and chase it full time”. His results since, such as his performance at Challenge Almere-Amsterdam, suggest this was a wise move.
Coming full circle
Now in his second season as a professional, Oosterdijk has high hopes of coming back to the Big Island to race the World Championships as a pro. In his only professional IRONMAN-branded event so far in 2022, Oosterdijk finished 12th at IRONMAN South Africa, but is willing to play the long game to get back to Kona.
Whilst he now has some solid performances under his belt as a professional, the Dutchman underlined how hard going from the front of races to being at the back of the field is initially.
He explained: “As an age-grouper, you can be in contention for the top steps even on a bad day whereas now the same performance as a pro might be equal to the back of the race, even with the exact same time and achievement.”
Going from winning to “losing” is a hard step to take and Oosterdijk also realises that in terms of sponsorship, turning pro was a risky step to take, adding: “If you win as an age-grouper, you might actually be able to get more product sponsors than as a professional at the back of the field.”
However, in the pursuit of his Kona dream, the risk is one worth taking. In Oosterdijk’s own words, Kona is “the ultimate dream and qualifying would be awesome.”