Steamer

I am going to be doing my first 12hr race with a power meter, and although I have some expereince in using it for training, I haven't really yet attempted to use it a guide to pacing on such a long event.

I have done a fair amount of searching on the internet for this kind of guidance, but the information is pretty thin out there. Coach Friel has posted some information how an 8-hour Ironman racer would need to expect power outputs in the range of 50-60% of FTP.

Can anyone validate this with their own experiences? Does anyone have a recommendation on what level of power output woudl make for a good pacing effort for the early part of the race, say the first half or 2/3rds. I would expect my effort to creep up towards the end, as a attempt to leave it all on the course, but I won't have a good negative split if I kill myself in the first 6-8 hours. Thoughts?

anotherbrian

Golden Cheetah says my IF has varied between 60-70% for 15-19h efforts. Rides that I felt good on were on the high side, rides I had knee trouble on and slowed were on the low end. That's total time, so there is typically 2-3h off the bike in that. Zero averaging of power is turned on on my Garmin's, though I don't remember how GC handles the calculation.

Since last summer, my CP at 2h is ~82% of FTP, but then drops to ~62% for 2h-5h. Both of those are way below the projected curve but a consequence of stopping at the typical double century rest stops. By the slope of my CP curve (not the projected one), it looks like I should be able to keep closer to 80% of FTP at 5h, but I'm skeptical that I could actually do that.

Steamer

Thanks!

Yeah, I tend to think the projected CP curve in golden cheetah is hopelessly optimistic at time scales beyond two-three hours or so. I don't have any of my own (real) data beyond 4 hours, and even those 3 and 4 hour rides for which I have power data were nothing remotely like maximal efforts.

It was pointed out to me very recently that Friel's range of 50-60% of FTP for an 8 hours IM bike recognizes that you have to leave something in the tank for the marathon. Obviously, I have no such issue. and so that range is probably a bit too low for a 12hr bike. So, based on this, and the numbers you have for IFs on longer rides tends to suggest that I should be able to pace in the 60-70% range. If I start out the first 3-4 hours at 68-70%, and find myself getting behind on my fueling, then I may need to knock it back to 65% or even a touch lower.

Even without a super precise pacing goal, I know if I was left to my own devices, my enthusiasm would probably have me riding at 85% (or even higher) for the first couple hours. That would not be good.

hamster

Going off what I think my FTP is, on 6+ hour rides, I consistently see 62-65% of FTP for 6 hours and 60-63% of FTP for 8 hours. I only had two rides with a power meter that stretched in the vicinity of 12 hours. The faster of two was 55% of FTP.

That said, I'm not completely certain what my FTP is (I never did a full 1-hour stress test). The metric I'm reasonably certain of is my 10 min power and I'm estimating the FTP at 80% of 10 min power.

Also, these results are not from steady-pace races but from hilly rides where I'd go closer to 90% uphill and coast downhill.

Steamer

Interesting. My 10 minute max power is only 105% of my FTP. I suspect that's lower than most people, though. I do lots of Z3 and Z4 work, and not much else, it seems.

I bet if your rides were flatter, and steadier, your average power numbers on those long rides would be higher percentages of FTP than what you are seeing. So perhaps, my targets are more in line with 65% or so, with some expectation that this could be overcooking things a bit at that pace. The pressure is low for me to get this right. I really just consider this race to be a learning experience. It's ok if screw it up a bit.

Steamer

Well, I ended up averaging 60% of my FTP. Based on how I felt when I stopped riding, I am not sure I could have ridden a whole lot harder.

However, I ended up riding the first 40 miles too fast (75% of my FTP), partly because of pack dynamics (drafting is allowed). In retrospect, I probably would have done better to ride on my own or find a slower group, because that hot first couple hours sorta messed me up for the rest of the day. If I had ridden the first couple hours more conservatively, I may have done a bit better than the 60%.

hamster

60% is pretty good, I think. I just had another long ride, went faster than usual in the beginning, and I was seriously drained after 5:30 averaging ~68% of FTP.

I made this plot from my last 4 centuries and one double:



It's curious how work stays in a narrow range on a wide variety of routes. Red was a flattish double century, yellow was a climbing century where climbing didn't even begin till 1:40 (the horizontal fragment around 50 min is fixing a flat), and purple was last weekend's ride (mostly up, up and up till 480 min). I ran out of juice at almost exactly the same time and amount of work on purple and light-blue rides.

anotherbrian

Thanks! I was going to ask how you did that as I've wanted better data visualization than I can get from GC, but then realized I should be able to figure it out with Perl and Apple's built in Grapher app.

Here are four of my doubles since last summer. I have a couple more I could plot, but would have to piece together from multiple files (Garmin crashes).

The orange ride is the only one I actually used the power meter to pace myself (20k ft of climbing, and I wanted to make it to the end. It was mostly a see-saw of climbs/descents), and ended up bonking at ~900min, but after ~30min off the bike and another ~20min coasting to the bottom of a hill, I was back on my original pace (or even stronger). The green line was from an allergy-induced zombie ride (~15k ft) that I don't even remember finishing. I remember looking at the data the next day and being shocked at how long I was on the bike ... it was the volunteer ride for the main event and I was solo the whole time (at ~500min I lost a rear brake pad mid-descent and stumbled around a long time trying to kludge it back together). Blue is from a ~15k double that I had knee trouble at late in the ride, and red is from a ~9k double.