Indoor performance in summer - heat?

neeb

I'm pretty sure I'm fitter for practically all types of "real" cycling at this time of year than I am in the winter, but when I do a 2x20 indoors now I'm about 3% down on FTP compared to at the end of the winter, even though I'm much faster on the road than I am at the end of the winter / start of spring. The second interval is particularly difficult... I do much more FTP intervals in the winter though, so I'm wondering if it's just that I'm more trained specifically for the interval sessions in the winter, or whether it's just that the heat at this time of year makes it impossible to perform as well indoors. Tonight although I had the window open and a huge fan on as usual, and downed a pint of water between the two intervals, it was about 28C indoors and I was certainly sweating buckets...

Herbsman

Training indoors in the summer?! Are you mad?

neeb

Herbsman wrote:

Training indoors in the summer?! Are you mad?

Perhaps...

No more than once a week, but the roads around here are just too rolling to be able to maintain an FTP-range power output constantly, and I think it really helps to keep that system "topped up" during the summer when most of my riding has a much more variable power profile.

amaferanga

What power meter? Are you zeroing it or allowing an auto zero between intervals?

neeb

amaferanga wrote:

What power meter? Are you zeroing it or allowing an auto zero between intervals?

Powertap G3. Good question - the auto zero is turned on, but I'm not sure if I stop pedalling long enough between intervals for it to kick in. There's no indication when the auto zero is working of course. It's actually more likely that it auto zeroed last night as I stopped for about 3 or 4 seconds between intervals to adjust the fan.

I've often wondered about this - the hub must get quite warm near the end of a 20min FTP interval, so maybe the calibration would be different then that at the beginning. But then, would you want to auto zero it right at the end of an interval (before 5 or 10 minute recovery) when it is at its "hottest", or maybe right before the second interval after it has warmed down a bit? It certainly isn't going to be zeroing during the intervals..

amaferanga

I don't think much heat will be generated within the hub itself, but the room temp may go up a few degrees which will eventually lead to errors unless you do a zero. I'd always manual zero between longer intervals.

Alex_Simmons/RST

Heat (esp indoors) can easily have a impact on sustainable power production greater than the drop you report. There can of course be other factors as well (fatigue, sleep, stress, diet, hydration, actual fitness etc) and as already mentioned, validating the data itself.

neeb

Yup, did another session last night and it was like night and day - much easier. But it was much cooler and especially less humid. I also zeroed the meter just before the second session.

Does anyone know roughly how much difference one calibration point on the powertap makes to estimated power at FTP? Say if I get a calibration value of 198, and then later recalibrate it at 197, how many watts difference will that make at 250-300 watts?

The manual calibration sometimes seems to jump around a bit, and it seems to be sensitive to things such as the position of the cranks. If I repeatedly recalibrate it often seems to give different values one or two points around an average.