The Ironman trademark (the second link is to one of the many Ironman registrations) is an extremely valuable trademark to the World Triathlon Corporation. The WTC works to protect its unauthorized use (though sometimes I do question their authorized use). I have heard questions before from other triathletes about how they can use the Ironman word mark, whether in blogs, on t-shirts, in articles.
Ownership in a trademark doesn’t convey the right to remove the use of a word from English. Instead, it provides an exclusive right to prevent others from using the mark in a confusing way, one that may damage the trademark owner’s goodwill in the mark or the mark’s own ability to differentiate the underlying product or service from others.
Consistent with this, the public doesn’t always need to request permission from the trademark owner to use the trademark; that permission is only necessary in certain (but many) situations. Permission isn’t necessary when the use meets the legal definition of “fair use.” Some uses are frequently considered fair, such as a 15-second clip of a motorcycle stunt on the evening news, or a professor’s copying of a portion of a newspaper article passed out in class. Comparative or nominative uses are often considered fair, as well: if BMW names Mercedes in a commercial to say how it outperformed their car, for example, that use is likely not infringement.
The use that many people worry about and have asked me about likely falls under fair use. It would be fine to write an article about your experience at Ironman Lake Placid and use the Ironman trademark in the body of the article. You’d be okay writing a book about your journey to the Ironman World Championships and identifying the various races you competed in as Ironman races. You are using the mark only because you are naming the specific event, and identifying the event without using the trademark would be unduly burdensome. Imagine how difficult it would be to describe the event without using the trademark: for instance, last November, I competed in a branded race where I swam 2.4 miles, biked 112 miles, and ran 26.2 miles in Tempe, Arizona, versus, last November, I did Ironman Arizona.