Thinking about my IMAZ bike split

I know its very dangerous to set and adhere to time goals in an Ironman--overall or on any of the three splits. How I feel on race day, the conditions, etc may very well dictate a modification of my level of effort.

That said, I have enough data to make an educated guess at this point.

Back in 2007, I biked a 2:24 at Eagleman and a 5:06 at IMFL. I think these courses are similar and I think the conditions on race days were reasonably comparable. I averaged 223 watts for the half and 211 watts for the IM. I ran well off my H-IM bike but I had a disappointing run at IMFL. The ratio between my AP at IMFL and EM was 211/223=0.95. Most knowledgeable long-course coaching types say that your bike should be in the 80-85% of FTP range for a Half and 70-75%. This implies that your watts in an Ironman should be about 87.5% of your watts at a H-IM (all things being equal). This says I probably should have averaged 195 watts at IMFL and not the 211 I did average--perhaps riding 10/15 minutes slower would have saved me 30+ minutes on my run.

I just did a 2:29:30 H-IM equivalent at SkipJack (my average pace over 66 miles adjusted to 56 miles). SkipJack is predominantly on the Eagleman course. I think the conditions were a little slower at SkipJack than they were back at EM in 2007. I averaged 221 watts for the 56 miles and ran about as well as I could hope to run given my current fitness (8:10/mile). Also, I actually rode at a higher output (225 watts) over the last half of the race so i feel like 221 watts is a good number for my H-IM power traget.

so, if I take 87.5% of that I get an power target of 193 watts for the IM distance. Given the cubic relationship between power and speed this would imply that my average speed would be 4.6% slower than I did at SkipJack. I averaged 22.47mph at SkipJack so this suggests that if I averaged 193 watts for a similar IM, I 'd average 21.5mph.

Now, IMAZ has the long, gradual climb (and descent) that you take three times and it's logical to assume that it's a slower course than Skipjack/EM or IMFL. To determine how much slower, I took the 100th and 500th fastest times at both IMAZ and IMFL over the last three years and compared them (I was 245th at IMFL07). The snswer I get is the 100th fastest bike split was 3.2% slower at iMAZ (compared to IMFL) and the 500th was 3.4% slower. So, I'll estimate that IMAZ is 3.3% slower thn IMFL, all things else being equal. This turns my 21.5 mph into 20.8mph. This translates into an estimated IMAZ time for me of 5:23.

5:23 seems like a reasonable number and wouldn't kill my chances of getting to Kona. Of course, if raceday conditions are a lot worse then, this calculation is not valid. That said, it's possible that conditions might be a little better than we had at SkipJack and I could actully go a little faster.

The other thing I plan on doing is raising my FTP by 5-10 watts in October with a lot of Computrainer time--I think this is doable and this might give me the option of riding at closer to 200 watts on race day.

In any event, I'd say a best guess of 5:15-5:30 is probably pretty good right now....

I'll return to this topic in the last few days before the race.