I have been training for IMMD (recently transferred from IMCHOO) and I am having quite some issues with maintaining what should be my target IM power over long periods. This will be my first IM, but I have done quite a few halfs, all of which I overbiked quite badly, so this is clearly a bigger issue. For reference, here are some of the more recent ones:
Oilman 70.3 2012: 5:21:05 (41:28, 2:36:35, 1:57:53)
Oilman 70.3 2013: 5:34:08 (38:58, 2:52:56, 1:58:06)
Galveston 70.3 2014: 5:25:40 (38:45, 2:38:43, 2:02:24)
To compare, my open half marathon PR is 1:26:42, and more recently, I ran 1:31:20. Recognizing this, I consciously decided to back off the bike a lot in my last longer race (1 mile swim, 40 mile bike, 9 mile run) to get the following result:
1 mi/40 mi/9 mi: 3:46:02 (33:52, 1:58:28, 1:09:25)
To complicate things, I don’t have a power meter, but I do most of my training on my CompuTrainer - so in essence, I train with power, but don’t race with it. I have tested and retested a few times to get an FTP of 265 (6’3", 190 lbs), using the Trainerroad 20 minute test protocol. Using this FTP, my indoor workouts all seem fine up to ~90 minutes, but anything over, I am having quite a bit of issues in ranges that should be easy cycling, including a rather noticeable cardiac drift of ~8-10 bpm. My weekly volume on the bike is not great, with my bike TSS hovering around 250, so I would assume this is one of the issues.
Based on feel, a 2:30 min endurance ride with a NP of 186 felt about as hard as all of the above 70.3s, if not a bit harder - which is of course far too hard. The question is - what combination of lowering target power and training can I do between now and 9/20 to address this?