I found an interesting survey entitled “CORRELATIONS BETWEEN ANNUAL TRAINING PATTERNS AND RACE PERFORMANCE IN MALE, NON-ELITE, IRONMAN-DISTANCE TRIATHLETES”. It’s a few years old and was hosted on trisurvey.net which is now on a link farm. The archived version is here, but lacks the images:
http://web.archive.org/web/20050311105743/www.trisurvey.net/ironman-distance_triathlon_study.htm
Anyone got a copy of the original paper?