Origin and age group of the fastest amateur triathletes competing in 'Ironman Hawaii' between 2003 and 2019.

Little is known about the prevalent nationalities among the best-placed athletes participating in "Ironman Hawaii." Moreover, the age at which athletes achieve their best performances remains unclear. The present study aimed to compare the prevalent nationalities among the athletes, their respective placement among the top five, and the performance difference between the different age groups in 'Ironman Hawaii' from 2003 to 2019. A total of 30 354 amateur triathletes were selected from the Obsessed Triathlete (OBSTRI) website. A "TOP 5" division filter was applied for further analysis, resulting in 1 851 athletes being included in this study. Among the male runners, Americans participated the most in Ironman events (39%), followed by Germans (10%). Among female runners, Americans participated the most (54%), followed by Australian runners (8%). Male Americans also featured most among the top five (30%), followed by Germans (16%). Female Americans were the most prevalent among the top five (47%), followed by Australian Americans (10%). There were no significant performance differences ( p  ​> ​0.05) between the 25-29 and 40-44 age groups for either sex. The 45-49 age group presented significantly worse performance than the 35-39 age group for both sexes ( p  ​< ​0.001). North Americans were the most performant and frequent participants in "Ironman Hawaii." The expected performance decline due to aging was observed after 45 years in both sexes.