Sprints with the PowerTap

I mentioned some oddities I experienced with the powertap I currently have on the bike I'm riding a few posts ago - ya'know, the whole exact same power readings during a sprint deal.

Here's a a screenshot from the download of yesterday's file where I was doing some sprints:

one thing to note is that when I stopped pedaling, I then glanced at the PT head unit as I was coasting - it kept reading the same value for a bit - and this observation is reflected in the download.

So, this observation would suggest that the PT is doing some unknown filtering in their data acquisition. This could be good, or it could be bad - in the case of short efforts , it appears that it's doing some weird things as it relates to reality.

Not that this sprinting observation really matters in the grand scheme of things (it's been kind of refreshing for the past couple weeks not to give any credence to the flashing numbers on the power display!) - but it is a worthwhile thing to note.

Speaking of power meters - did y'all see the dueling press releases from ergomo/gita this past week?

Guess that is a partial explanation as to why I never got an ergomo to evaluate from the "important folks" at ergomo-usa. Then again, the excuse I continually got was that "there just isn't any availability right now for demo's" - or words to that effect - which from the sounds of the Gita position is a factual statement...

Anyway - I reckon my original thoughts on the ergomo still have some relevance:

-measure one leg and double it and all the doubt that that brings up

-ease of installation

-reliability of "zero-ing" out the unit prior to riding

-measure one leg and double it and all the doubt that that brings up

did I mention "measure one leg and double it and all the doubt that that brings up" ;-)

Seriously, though - I reckon if a gadget helps you ride your bike more intelligently/purpose/reliably then that's a good thing.

I used to keep training logs back in the day where I'd actually write things down - that was a good tool to make sure I was doing what I had set out to do on a given day. Nothing like the satisfaction of writing down HR's and times and distances and RPE's in that journal entry for the day!

Downloading a power meter file can have a similar effect on training, in my experience.

Cycling Weekly (cont)

[cycling weekly] Do these principles differ according to the rider's strengths/body shape/riding style/event?

[kraig] The most important principle, IMHO, is understanding that positioning is a process that relies on the experienced use of the best measurement tools. Folks are pretty different in the positions they wind up with, but a good process will guide them along to the best result. If one focuses on the process the results will come.

[cycling weekly] In the case of each of the following, is it possible to say which is best and what sort of rider should use it? (a very stretched out position like the Superman, but within UCI limits. a Tuck position a la Landis and Leipheimer. A wide arms position like the UK Track team.)

[kraig]I don’t think it’s really possible to say which is best without testing it out. I’ve seen the Superman “work”, I’ve seen the Leipheimer position “work”.

[cycling weekly] Why do the UK Track guys ride with their arms so wide, do you think? Similarly what was so good about the Landis/Leipheimer position?

[kraig] I’m not sure why – I know that those guys test at a wind tunnel under the guidance of Chris Boardman (who is fond of telling Anthony McCrossen of cycling.tv that arm position doesn’t matter), so I’m sure they’ve got some evidence that suggests it’s the way to go. Maybe the ex-2006 Tour de France winner (I'm not quite sure how to phrase that - maybe I'll have to consult Floyd's legal team on that one??) just liked the way it felt for his hip – or he simply thought it was “cool” – or he had documented the supply side (power with his power tap) and the demand side (using the data from the tunnel here in san diego), and found that to be the best combination. Levi also uses power and wind tunnel data to guide his positioning decisions – it’s got to work on the road, though!

[cycling weekly] How important is it to get 'narrow' in the hands/elbows/shoulders/knees?

[kraig] People pedal differently, and this can affect the optimal position. I like to do sweeps on elbow width on pedaling riders under load (some facilities can't load up riders with any resistance, which is something to think about) in order to understand how axial force changes – narrower isn’t always better.

The PowerTap Experience

I've been riding with a PowerTap for the last couple weeks or so - one week in tandem with my SRM Pro on the Pinarello, and this past week or so by itself on the Cannondale I'm transitioning to.

I've done a myriad of different efforts and rides with the PowerTap, and there's a few things during this experience that have really made me think a bit.

First off, damn, trying to download the PT on a windows Vista machine was a total pain! I have an older hard wired PT pro with a serial download cable. I downloaded the newest version of the PT software off of the saris site, and couldn't get it to work since Saris is no longer supporting serial connections and only supporting USB connections (I'm no expert on this stuff, so it's entirely possible that I just didn't push the right sequence of buttons and rub my belly while tapping my head just so in order to make my configuration work out). :-)

Next, I used the CD that came with the power meter (that I bought used a few years back and had re-furbished by saris after it mysteriously just stopped working a summer or two ago) - the software I tried installing was Link ver 1.04 - and that software also wouldn't work.

I tried many times with the PowerLink Lite CD, that also came with the PM, to just download the data - and eventually got that sucker to work... Several times during the past week, though, I got weird downloads - just crap data with big spikes. These (obviously jacked up) downloads went away on a second attempt at downloading, but really, it was just a painful experience...

Additionally, I've been doing some sprints lately with the PowerTap, and it just seems really odd that I'm able to generate the exact same wattage for 3 or 4 consecutive 1.26 second samples. I seriously doubt that I'm that consistent over that 5 second-ish period. I'm not sure what to believe with that data... Oh, where is the SRM config that will work on this bike??? :-) It looks like this coming Monday I'll have all the parts I need to make that happen - but I reckon I'll have some challenges I didn't anticipate when trying to make it all work... If there is one thing I have learned in the past 35 years, it's that nothing is "easy"! :-)

The last thing I've been trying to get my hands around is the whole "interval" feature of the PowerTap. I've always taken for granted how the SRM integrates this feature. I like to see how things went during the last interval I did while I'm rackin' up those bonus points coasting back down to the bottom of the hill. With the SRM it was as simple as hitting the set button at the end of the effort and seeing the time of the interval, and the average watts of the interval. If I wanted to review the first interval while coasting down during the third interval (to see if my power to RPE ratio is in check...) I just simultaneously hit the "mode" and "pro" buttons (or whatever sequence that is that I instinctively do now...) and cycle through the interval data of interest. Takes a few seconds or so...

With the PT, I haven't yet figured out how to get the same information as the SRM until I download. But then again, I haven't RTFM. Anybody else figured out how to actually make use of the PT interval functions???

Anyway, a side benefit of the whole PT experience is that I don't really look at the display while going hard anymore - I just kinda "go hard" - ya know ridin' by feel, all retro and stuff! Interesting to note that I am not limited by the flashing numbers with the PT, and I go just as fast - well, faster on some efforts recently - than I've done in the past.

'Course - I'm a couple kg's lighter than I've ever been before too - so that confounds the whole "pissed off at the powertap" effect! :-)

Seriously, though, if anyone can help me make sense of the whole powertap interval function thing, I welcome the input!

Cycling Weekly Question #2

[cycling weekly] What general principles would you look to include in a good aero position?

[kraig] After directing 1000+ wind tunnel runs with over 90 athletes (including hacks like myself all the way up to world champions and tour de france podium finishers), I have seen many things that re-inforce the position that the aerodynamics of a pedaling three-dimensional human is a very individual thing. One can generalize, but really, in this context, “generalizing” is synonymous with “guessing”. I recommend using the best tools at your disposal to help quantify both the supply side (power generation) and the demand side (aerodynamic resistance) during the position evaluation process. The experienced use of the best tools can speed the process up.

Here’s some more of my thoughts (prior to doing a bunch more wind tunnel work which has changed my mind a wee-bit):

http://www.biketechreview.com/performance/pareto.htm