Training-intensity distribution during an ironman season: relationship with competition performance A Spanish group has studied in Ironman Triathletes whether there is a connection between the intensity in training and the Ironman competition time. The largest part of the training was carried out in deep intensity while the race was at a higher intensity.
It showed that a better competition time resulted when the athletes trained in a more deeper intensity. The very insightful work can be found under https://pubmed.ncbi.nlm.nih.gov/23921084/