Last night I went hunting for a PB and came away with nothing but frustration. What was supposed to be an attempt at a new 10-mile time trial personal best just didn’t go to plan. No excuses, no obvious reasons, I just was low on power (but high on heart rate) and didn’t feel fast in any direction (according to Mywindsock, I had a tailwind on the first section, it didn’t feel like it!).
The poor performance has annoyed me more than it should. Mostly because I can’t really understand why. The new arm position has felt fast in practice runs; I don’t feel more fatigued than usual and I seem to be the only one of the 15-odd competitors last night that was significantly off the pace. I can’t even call it a ‘slow night’.
I’m guessing the other riders had different experiences, but one thing that struck me was that when warming up, I was hitting roughly 40kph for about 200W (which does suggest a slight tailwind) on the westbound stretch. However, in the actual race I had to put out 270W or more to keep my speed at 46kph.
So that meant it took a 35% increase in power to achieve a 15% increase in speed. Interesting, if only to make you realise that the faster you try to go, the exponentially more power you need to fight the air resistance and drag. Ergo, the more important that the aerodynamics of both the bike and the rider become.
For me, the biggest frustration from last night (aside from the slight drop in power, more on that in a moment) was the sense that the new position (see previous blog) didn’t make me as slippery through the air as I had hoped. If anything, the change seems to be for the worse.
I’m trying not to jump to that conclusion after just one race, and will stick with it a while longer before reverting back to the old setup; but clearly it wasn’t an instant success, despite my head feeling lower.
And in fact, the power / speed figures might actually indicate that the position wasn’t to blame. In percentage terms, I was 2.3% slower last night than my PB run on that same course. In terms of outright power, my average for the 16km was down 2.9% on the PB run. Which (I think) could suggest that if I had held the same power last night, I would have gone quicker.
Now, of course, position has a huge impact not only on aerodynamics, but also the ability to drive power through the pedals, so one thing I need to look at is whether my ability to drive power in the new position is compromised to the extent that I end up being slower overall (despite a more slippery shape), or whether I can actually get the power out and last night was just a bad one.
Plenty to be working with Martyn Harris and friends on in the coming days and weeks…
One other difference between last night's run and my PB run on the same course was that on one run I had the special 'aero hydration system' fitted to the front of the Giant Trinity triathlon / time trial bike, and on the other I didn't. Can you guess which way round it is?
If you've seen the photo above, you know the answer. Last night I ran without the hydration system. I've always thought that it's a little cheeky to use a non UCI-legal bike in a cycling time trial and so lately I've been leaving off the hydration system when not riding triathlons or duathlons, just to try to get the bike as close to UCI-legal as it can be (and frankly, I've never really bothered to find out if it's supposed to actively help the bike's aerodynamics).
After last night's performance, however, I did some research and it does seem that Giant does indeed make the claim that the Giant Trinity (in triathlon guise) is faster when you have the hydration system fitted. Maybe I can live with myself if I stick it back on for the next local club TT (I guess some open TTs are a bit more concerned with UCI rules...) just to see if it really makes a difference.