This week marks an important transition in my Ironman training: 20 weeks until the big day. *Gulp* In just five months time, I will be swimming 2.4 miles, biking 112 miles, and running 26.2 miles–all within (I hope!) the official time limit of 17 hours. Having talked to experienced Ironman triathletes, I knew that the “20 weeks out” moment was a major transition in the training plan. This past Sunday, I pulled up my schedule, and I noticed the shift. Now that it’s Friday, and I’ve made it through 5 of the 7 training days: I’m feeling the shift. So, …