Personal best times in an Olympic distance triathlon and a marathon predict an ironman race time for recreational female triathletes In the long-distance area there are many variables that have an impact on performance. For example, it is known that a deep body fat correlates with a fast competition time. For Ironman triathlets, it is a bit more difficult, because variables of the body construction show no connection with the competition time.
On the other hand, the marathon best and the best time via the Olympic distance are significantly associated with the Ironman competition time in women. On the basis of this connection, you can estimate the ironescence in women, the formula can be found under https://pubmed.ncbi.nlm.nih.gov/22784279/