A comparison of anthropometric and training characteristics of Ironman triathletes and Triple Iron ultra-triathletes We have compared features of body construction as well as the training of Ironman and Triple Ironman Triathlen. It showed significant differences in physique as well as in training.
Both athlete groups are common that low body fat is advantageous. In the triple Ironman triathlets, the training volume appears to be on the bike and in progress, while Ironman triathlets, on the other hand, the speed in cycling. The abstract of the study can be found under https://pubmed.ncbi.nlm.nih.gov/21834654/