Once a source of "Not all you want to know about Texas Adventure Racing," but now just some "leisure" adventure through the eyes of "The K-SPoT"

Monday, February 22, 2016

Stages Power Meter Comparison Part Deux!

Alright, fresh off of a 3rd agonizing FTP test that I am actually satisfied with...short story is, the last two tests were painful--1st one I went out too hard too early and the 2nd one I suspected that something was off with the Computrainer. To show that I wasn't just whining on that 2nd disastrous test, I have comparison plots for that "bad" 2nd test and my latest "good" 3rd test. First the bad:

Click on the image for a better look. There is a lot of data plotted here so I want you to focus on the solid blue and dashed red lines. You can see that the Stages power meter (red dashed) predicts a higher power output than the Computrainer (blue) of about 50 watts at any given time during the 20 minute test. And, yes, I calibrated my power meter. As soon as I started, I knew something felt wrong because, yes, it was hard, but too hard considering I was mashing and the Computrainer was telling me I was "only" putting out barely 250 watts during the beginning. As you can see, I gave up at about the 3 minute mark, shifting to an easier gear. If the Stages power meter was correct (which I think it was), I was putting out over 300 watts during that time period--I wasn't going to be able to sustain that for 20 minutes even if I decided to enter a very, very, dark place. Another telltale is that for the first minute I was trying to lift my pace since Computrainer was saying I wasn't working hard enough, but the power seemed to keep constant at around 245-ish watts. On the other hand, Stages was showing that I was indeed lifting my effort steadily from about 300 to 325 watts.

Now the good:

Same idea here, but totally different result! Look how magical the plot is--Computrainer and Stages data are almost on top of each other! In fact, towards the end they almost look identical in a mean average sense. Not sure it is because either Computrainer or Stages corrected due to "warm up" or if it was an anomaly due to my erratic surging while approaching puke mode. This tells me that the Stages and Computrainer can be expected to match each other if all is good with calibration, warm up, etc. Yay data!!

I do have other interesting plots of heart rate and speed that seem to support my armchair-ing above, but I am done nerding out this time around. Yes, I know, HTFU...but there is such a thing as smart HTFU-ing...I think...

Monday, February 01, 2016

Stages Power Meter vs. Trainer Road and Zwift

So, it's been a while since I did a pretty plots blog, so here it is! I recently joined the power meter crowd (yes, finally!) and wanted to see how the power estimations of Trainer Road and Zwift compared. Note that I am using the Tacx Booster on setting 2 along with a speed/cadence sensor--both Trainer Road and Zwift use published power curves for the Tacx Booster to estimate power generated based on speed. First off is Trainer Road vs. Stages. The comparison here is really good! The averages actually are pretty spot on. Stages data has more variability, which I think should be expected. But in all, Trainer Road seems to have this one dialed in.
 On the other hand, Zwift is way off. I kinda suspected this because I was barely getting winded while pumping out 270 watt sets. As shown in the plot below, power can be off by as much 60 watts! Yes, Zwift makes you seem like a monster, but it is not real. Especially, during three sprints (the three spikes around 12 to 15 minutes) they diverged quite a bit--Zwift seemed to plateu before 400 watts, but Stages went all the way to 800 watts. I believe the latter because I was mashing super hard and it seemed that Zwift just flatlined.
Again, I want to emphasize that these findings are solely based on using the Tacx Booster and Stages FSA EVO386 crank power meter--your results will most likely vary. Well, there it is.  Enjoy at let me know what you think!