First attempt at powertap numbers. Meanings?

Discussion in 'Power Training' started by stormer94, Aug 18, 2005.

  1. stormer94

    stormer94 New Member

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    Well, it's still not working right. It's still dropping the connection. BUT, for whatever reason, the higher the wattage, the less it "SEEMS" to do it. Like it's "almost" trustable. But it will still drop the mph numbers...??? I don't know. I've tried a different wheel, a different computer, and now a different sender. Do they need to be "broken in"?

    Anyway, here is what I found (see image) while testing this setup on my TT bike in an aero position. Did (2) 20 min efforts, with a 10 minute recovery. No tricky wheels, no aero helmet, just the position.

    Also, my ass muscles ache more in the TT position. Does that sound right?

    Also, I feel I develop more gross power upright than in an aero position, normal?

    I did an out and back on the same course. Out was 2:44 pace @21.9mph average watts was 240. Back was 2:29 pace @24.1mph average watts was 226. Slight, 1mph or so breeze on the return. Also, I think my position was better on the way back, my upper torso was more warmed up, and I felt lower, like my chin was about 4-5 inches from the top of the stem. Possibly I was not warmed up enough, that's debatable. Also I ran this about 5:30pm. Normally I train in the morning but it was freaking cold here today so I ran in the afternoon, and I had a HUGE lunch, Philly cheesesteak sandwich, fries and a salad. Not sure if that would have an effect or not. I'm guessing not, it had been about 4 hours.

    On the first one I watched the powertap and saw 400-500w for the first bits while getting up to speed and then watched the watts drop and settle for the duration. The second one I thought , "Hmm, 240 watts average on the first one, I'll just try and hold about 250 from the start and see what happens". At about a minute, the HR was still not up, so I just hammered it up and then watched the average. The second one would likely have been a "touch" faster. I also underestimated my return speed and had to slow just a bit for some in town traffic, you can see a small dip in HR at the end of the second one. It was from that. MAYBE 1 second overall on pace.

    So, what am I looking at?
     
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  2. RapDaddyo

    RapDaddyo Active Member

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    No.

    You will likely have several aches and pains after a sustained effort in the aero position (legs, glutes, back, neck). This will abate over time as you practice in this position. Most people recommend that you practice the aero position about once/week.

    Yes, and you may well be generating less power in the aero position initially, but with practice you will probably be able to generate the same power in the aero position. Don't be too quick to toss out a position due to an initial power loss. I can't imagine how many hours Boardman must have spent in his aero position before his hour record runs. The key thing is that your PM enables you to experiment with aero positions at the same power and instantly see the results (speed) under known grade and wind conditions. It's a good idea to find a place that you know to be board flat (or even a slight downgrade) to do aero position testing. On the same day (and therefore, constant wind), you can run through several positions holding power constant and get immediate feedback. It's like having your own personal wind tunnel. Same thing with wheels, helmets, etc. Aero testing is when I really wish we had a track here in LV. But, there's one about 4 hours away.

    It looks to me as though two factors contributed to your higher speed at lower average power on the return leg. As you noted, you probably had a slight headwind on the outbound leg, tailwind on the return. Second, the outbound leg is a slight net upgrade and the return is a slight net downgrade. These two factors could easily explain these differences. If you changed your aero position as well, that makes three factors and I'm not sure it's possible to determine the exact contribution of each unless you knew the wind exactly. BTW, for TT and aero position testing it's a good idea to buy a portable wind speed device, something like this: http://www.ambientweather.com/lacrteeahawi.html. Kestrel is the gold standard, but this one is good enough. Wind is really way more important than you may think and comparing data from tests on different days requires knowing the wind precisely.

    You didn't ask, but I'll volunteer that neither leg was optimal in terms of pacing strategy. I looked immediately at your power line and it was obvious that your pacing strategy was constant power. If I ran the same course, you would have seen huge spikes (>100w) in power in those places where bike speed slowed and a decrease in power in places where bike speed increased. Although I do agree with the relative average power on each leg (higher power on the upwind, upgrade segment; lower power on the downwind, downgrade segment).
     
  3. RapDaddyo

    RapDaddyo Active Member

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    Scratch that. I think I was looking at your HR line. Where's the power line? Anyway, looking at your speed line, it is equally obvious that you didn't increase power in the upgrades and float on the downgrades as I would have.
     
  4. F1_Fan

    F1_Fan New Member

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    For some reason he's showing us data frmo Polar Precision Software and not the PowerTap.

    If the PT is dropping out I'll bet the wireless transmitters from the Polar are the cause.
     
  5. stormer94

    stormer94 New Member

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    I just remembered the Watt numbers and listed them on the image.

    I can't make the PT work the way it's supposed to yet (one piece of the pie is still causing problems, even when the watts stayed, the MPH would drop... I saw one time I had the connection and it still lost the reading), haven't tried to torture myself yet by trying to hook it up to my computer. I don't know that I could stand the frustration.

    Spent another 2 hours with it today... :rolleyes: Takes time to install, run wires, ride-test, get pissed, uninstall, try something else...

    Although as a serious analyzer of my information, I have seen a bit of hope in the brief bit of fun I had with it today. It was fun to see some additional information. Is it necessary? Who's to say. My TT pace is about where it's supposed to be, and where I calculate it to.

    My state TT pace was 2:39, 22.55 mph, these averaged out to 2:36, 23.00mph. Watts, HR, PE, LA, whatever it is, it all comes down to racing the clock. What gets you from "A" to "B" the quickest.

    I gotta rest up. I'm doing a century on Saturday, and again the next Saturday. Hope to beat my solo best of 5:43 (I suffered, poor nutrition and planning). Much smarter on long rides now.
     
  6. stormer94

    stormer94 New Member

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    It was pretty dang flat. The only up and downs, really, are the spots where the road may raise a few feet for a bridge, and then come back down again after the bridge. Other than that, nothing you can see or say, "right there", is the base of a rise... just flat. 15-20 feet elevation change over 7-10 miles.
     
  7. RapDaddyo

    RapDaddyo Active Member

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    Okay, then what accounts for your speed changes? Changes in grade are very difficult to "see" and changes in wind are very difficult to "feel." But, with a PM they are instantly perceived because bike speed changes while maintaining a constant power. Now that I have topo software, I have been looking at some of my regular training routes and I have been shocked to see the true elevation profile. I now don't trust my eyes to accurately see grade changes. But, my PM is infallible -- even slight grade or wind changes show up instantly.
     
  8. lanierb

    lanierb New Member

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    I honestly don't understand this. The powertap has to be the easiest thing to install there is. You run ONE wire down the top tube and down the seat stay, change out the wheel, and you're done -- 15minutes tops. It's easier than a regular cycling computer because you don't even need to install a wheel magnet/sensor.

    Try it totally clean, no polar etc, and I bet it works 100% fine.

    Lanier
     
  9. RapDaddyo

    RapDaddyo Active Member

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    I've looked again at your Polar data and have concluded that nothing of any value can be concluded from this set of intervals. Basically, there's too much going on and your power number is just an estimate from memory. Think about it for a minute. If I tell you, "I did an out and back TT test today. There was a breeze, but I don't know how much exactly. The course was relatively flat but the outbound leg gained a little elevation and obviously the return leg lost a little elevation. Plus, I changed my bike position on the return leg. And, BTW, my power number is an average and from memory at that. What do you make of my data?" You would (or should) say, "Based on what you've just told me, I have no clue what's going on. There are too many dynamic variables (grade, wind, position, power) to draw any meaningful conclusion." That's where I am.
     
  10. stormer94

    stormer94 New Member

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  11. RapDaddyo

    RapDaddyo Active Member

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    Well, they sure show up in the bike speed. Just look at your own file.
     
  12. stormer94

    stormer94 New Member

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    Yea, but only 2mph average, 10% difference on an "out and back". I don't know that I can put much stock in small changes in speed here and there (it's the overall average that makes the most sense for me). I feel that I tend come and go on things like technique, breathing, position, boredom, cadence, etc.
     
  13. RapDaddyo

    RapDaddyo Active Member

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    Are you kidding? Two mph is the difference between 1st place and 10th place out here.
     
  14. stormer94

    stormer94 New Member

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    True, but we were just trying to figure out the difference between the out and back speed, which I attribute to wind and a "SLIGHT" 20 foot descent over 8 miles. Which accounted for the 2mph. Effort was similar, speed was not, hence trying to find the reason. wind. :)

    Which is why I didn't take any particular stock with either number (2:44 or 2:29 pace) and used the average of them to come up with what I believe to be my correct pace of 2:36
     
  15. frenchyge

    frenchyge New Member

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    As interesting as this conversation has been, I'm not sure I'm seeing the point. Stormer, what are you asking for? Why post the HRM data instead of the power data? It seems to me that you did a test ride, and you're asking what the numbers mean. Well, you've done a 20 min interval at ~250W, so that means you can sustain 250W for 20 minutes. From that, you can estimate your 1-hr power (~93% of 20 min power if I recall correctly) to be ~232W. You can use that number to determine your W/kg and compare yourself to others, or estimate the 40k TT times you could expect for a number of different course/environmental conditions, or set training goals/zones, or estimate MAP, or any number of other things.

    The nice thing about training with power is that you no longer have to worry about slight breezes, or bumps in the road, or whether you should hammer your HR up to target, etc. Do some testing to establish a baseline, set some goals, develop a plan, and track progress. The basic training principles don't change just because you're using power, progress just gets a lot easier to measure.
     
  16. RapDaddyo

    RapDaddyo Active Member

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  17. stormer94

    stormer94 New Member

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    It is easy to install, unless your installation doesn't work, or a piece of the system is defective and you have to figure out which piece...

    You forgot about half the wiring, there is a cadence sensor too.

    I've ridden different bikes with this exact compenentry on it, and it was fine. There is something missing, something not right. Cycleops is working on it. I've gone through about 300 zip ties.... and a whole bottle of stresstabs...
    :p
     
  18. RapDaddyo

    RapDaddyo Active Member

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    I think it's been recommended about five different times by different posters, so I can't imagine you haven't focused on it, but are you absolutely certain you don't have a conflict with your other computers? If so, why are you certain?
     
  19. F1_Fan

    F1_Fan New Member

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    Most topo software (if that's what you're using) is complete crap on these scales (short bike rides). Interpolation from coarse USGS topographic maps isn't accurate.

    DeLorme TOPO USA 5.0 is hideous. Case in point... Hurricane Ridge, WA. TOPO USA says it's a 11% climb with sections of 20%. Complete BS. I've ridden it three times and there's no part of that climb any steeper than maybe 8%. My Polar 710i and Vetta 100A both agree with the well-established numbers of 5.5% for the main climb and 7% for the first bit from sea level to the park toll booth.

    The generated gradient maps from TOPO USA are laughable... Hurricane Ridge looks like a sawblade. The reality (verified by my Polar data) is that it's a very consistent gradient.
     
  20. stormer94

    stormer94 New Member

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    I originally also had a cateye double wireless computer on the bike. It was suggested that I remove the batterys from it. I did, no change. Finally removed the whole system, including the sensors and magnets, no change. I have had this bike at a coach's facility with his setup on it, and it worked just fine with the polar HRM. My polar HRM also worked just fine on his single speed bike with a powertap on it.

    So based on that. The cateye had no effect at all on it, on or off. The Polar HRM has worked just fine on this bike with a different PT (older original though), and my HRM worked fine on yet another bike with a PT. And all PT information and functionality was rock solid. Given that scenario, it is logical to feel that the polar and the PT are not conflicting and do in fact work just fine together (on other bikes). Nor were the PT and the Cateye double wireless conflicting.

    Also, apparently it's common for this coach to have you bring your bike and your HRM and he'll pop the PT on it and you test. So it seems logical to also assume that he's had no problems with any of the HRM's that have been through his doors.

    It's just some crazy intermittent dropping of the connection. I've even had connections and lost speed... I've seen connection okay and lost watts... but not as often,

    The coach and his equipment are 300+ miles from here, so I cannot test with his stuff against what I have giving me problems, and I have no one else to swap parts with or to give it the old "well, THERE'S your problem right there".

    I posted pics here and everybody felt the mounting was good and distances were good. Maybe an atomic bomb was exploded here many years ago and some fallout is giving me problems... :p Indian burial grounds... UFO's...

    I'm going to work on it again tomorrow after Polar gets back to me. Whatever it is, I'm sure it something minor that's been compounded by something else minor. I only have so many hours in the week to monkey with stuff like this, and it isn't helping.
     
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