Using a Powermeter during a race

Discussion in 'Power Training' started by bgoetz, Aug 7, 2013.

  1. bgoetz

    bgoetz Member

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    Does anyone look at their Powermeter while racing beyond maybe just a glance at it? If so how do you utilize it? The reason I ask is I just read an article claiming that Froom's attacks were pre-calculated efforts and he paced off of his PM. Apparently the idea was to ride FTP, 20-30 sec attack, settle into just under FTP. I race with it to look at my data afterwards and determine how well I raced and how I can better my training, but beyond a TT I have never really paced off of it during a race. Heck a couple weeks ago I rode the last 11 miles of a race solo and not once switched to a screen where I could see power. Looking at my data I put in a 20-30 sec hard anaerobic effort to create separation, followed by 4-5min VO2 to maintain/distance myself, and then settled into a sub FTP effort for the remainder.
     
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  2. JibberJim

    JibberJim Member

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    Do you race up any 40 minute climbs though?

    It's quite a different sort of racing to anything I have the chance to do, and I don't look at it.
     
  3. bgoetz

    bgoetz Member

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    Yeah, I definitely considered that his effort up a long climb is more of a TT type effort.
     
  4. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Yeah and that's where the PM info can help. IOW, if you're in a situation where you can choose to alter your pace for tactical reasons then the PM may be useful but if you're in the field and responding to what's happening not so much as you have to do what you have to do to stay in the race.

    So solo breaks or riding in a break and trying to manage your energy so you don't drop yourself out of the break or perhaps a bridging move or a long climb where you may choose not to drive the pace or stay with one or two mountain goats only to blow up and have the bulk of the field roll right by you. These are times when making sure you're not digging too deep a hole can be useful but in general in mass start racing you don't have the luxury of backing off if it feels fast and just need to do what you need to do.

    -Dave
     
  5. An old Guy

    An old Guy Member

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    Without information of how you finished ---

    Your last 11 miles was about 30 minutes. sub FTP was an easy effort for that length of time. I would expect that a group chasing would have caught you.

    But the goal of a race is to finish first not to put out a certain amount of power. If you looked back and saw no one approaching, your efforrt was enough.

    There are certainly times when power is important in racing. Solo efforts - time trials, long climbs, long chases. But the raw numbers have less importance than knowing how you recover during the race.

    It is also nice to know if you can accomplish your goal alone or if you need to get help from others. In the heat of a race sometimes looking at your power will give you better information than just going by feel.
     
  6. bgoetz

    bgoetz Member

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    Ugh! Yet another perfect example of a comment that demonstrates you have never raced a bike. 1st it was hot as heck, we were all feeling the heat, 2nd it was at the END of a hard race were I was solo another 5 miles earlier in the race and in the mix of another couple moves. We were all hot, we were all pretty fatigued, even sub FTP after the 4-5 min effort I put in @ VO2 was a tall order. 3rd there are things called race tactics and sometimes in situations like this, late in a race, those tactics create a group that does not work so well together. I took advantage of the dynamics of the field and finish about 1 minute ahead of 2nd, who was also solo. The rest of the field rolled in in smaller groups from being blown apart by just how hard the days racing had been.
     
  7. bgoetz

    bgoetz Member

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    Of course if you were there you would have just rode tempo off the front and blew right past me ;) BTW: the whole effort took right around 26 minutes
     
  8. ddalzell

    ddalzell New Member

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    TT and triathlons... absolutely..

    Road race and Crit... not unless I attack and try to stay away
     
  9. Johnny Mac

    Johnny Mac New Member

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    While I use a PM (SRM Dura Ace 7800 - PM5) on my Cervelo S2 criterium bike, I almost never look at the numbers during the race. I like to look at the numbers later especially when I do a cat. 3 race followed by a longer and harder Pro 1-3 race. Interestingly, in cat. 3 (7th place) at the most recent Torrance, CA. crit. for 55 minutes, I averaged 273W 144BPM HR (315 Normalized Watts) and for the Pro 1-3 race (23rd Place) my average power was 256W 140BPM (283W Normal) for 75 minutes. I always have about a 20W drop off in power from the first race where I'm trying to get into breaks or chasing them down to the latter races where I'm doing less chasing and more just staying in the pack with an occasionally attack or bridge to a break. I do feel a little tired in the second race but I think a lot of the difference in my power between the two races is psychological - that is I expect to be tired so I'm not willing to try much harder thinking that maybe I'll get dropped if I go too far into the red.

    One of the other interesting things I've noticed is that on my TT bike (Cannondale Slice RS) I use a SRM SRAM S975 PM (PM7) and my average power is about 326W for a 10 mile TT (21:28 or 28.0 mph) but my average power while climbing is around 360W for 20 minutes and 410W for 11 minutes. What I'd like to be able to do is to get my TT bike power closer to my climbing power for the same time.

    Does it seem reasonable to be losing about 10% power at the same HR going from the aero position on a TT to the more open position on the road bike while climbing. The other thing is that my cadence on the TT bike is about 100 rpm whereas my climbing cadence seems to be about 70 rpm.

    Any thoughts on this?
     
  10. bgoetz

    bgoetz Member

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    I tend to lose power in my TT position, so I would say it is normal. I would say it is no real surprise that you normalized a bit closer to your AP in a 1-3 crit vs a 3 crit, one you were tired and maybe a bit less active in the second crit because you are no longer the strong guy and have to be a bit more conservative. Two the 1-3 crit was likely smoother as the guys are better around corners. We don't have many 1/2/3 crits, but I can typically pick out the 3s in the field, in fact I usually end up right behind them on a tight technical corner, lol. Either case based on the #s I would say that course was not real technical, more of a drag race type course.
     
  11. daveryanwyoming

    daveryanwyoming Well-Known Member

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    Many if not most road racers lose some power when they jump on the TT bike. Ten percent is on the high side but it's not unusual if you just jump on the TT bike before important time trials. If you actually ride it one or more days per week or still have a 10% power drop after a big block of TT training (like before state or national championship time trials) then you might want to re-evaluate your TT bike position for things like max and min hip angles as your position may be too agressive and costing you too much power.

    You also might play around with lower cadence during some of your TT training. Many TT riders spin fast but some get better results by plugging away steadily at slightly larger gears so experiment in training and see what gives you the highest sustainable power in the TT position.

    FWIW, in terms of myself and the riders I've worked with for TT training, a 10% power drop in the aero bar position isn't unusual when folks first jump on their TT bikes but that gap usually closes to within 3-5% or less after people spend some time training on the TT bike and then we try to do at least one day per week in that position during the season if more TTs are coming up to maintain that adaptation. Some of the triathletes I've worked with actually produce better power in the aero bar position than they do on their road bikes which they rarely ride so it does seem folks adapt to the positions where they do most of their riding.

    -Dave
     
  12. smaryka

    smaryka Member

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    But be careful chasing power on the TT bike if you need to alter your position in such a way to get it that you become less aero. Generally speaking, the faster you go, the more aero you want to be, so if it costs you 5% of your watts to be in that position but you're going faster than you would with higher watts and a less aero position, then it's a no brainer. With a powermeter and a decent flat windless testing loop you should be able to use aerolab in Golden Cheetah to test various positions and watts and find the sweetspot.

    Also think about your head position, how well your helmet fits your position, how close together you can get your arms, etc. -- all the little wins that will add up to more aeroness. If you're doing a 21-min 10-mile TT then you're going fast enough to be more serious about finding those gains.

    However I agree that time spent in the position is what will improve your power there, so once you have a good aero position dialled in, improving your power is just a matter of adjusting to it.
     
  13. Johnny Mac

    Johnny Mac New Member

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    Thanks for this. I do a fair amount of aero testing using my 2011 Cervelo S2 road bike on the same closed course that my club does its monthly TT race series. The course is rectangular with a lap distance of .83 miles and the corners can be taken while pedaling. The wind on this course is usually very calm when I test at 7:00 to 9:00 A.M. and I use the local weather station information to compute the air density given the barometric pressure and temperature. Furthermore, there is very little elevation change (~7-9 feet) and the pavement is excellent. I have been testing mostly on my road bike with different wheels, water bottles (or none) and rider position on the drops, hoods, ect. I have found that even on my road bike that I ride all the time, that when I'm in the most aero position that my perceived effort and heart rate are higher at a given wattage. When I test, I use my SRM and try to keep power relatively constant across most tests (250W +/- 3%) and do a number of laps for each control or test. I always do a control test first with the same bike and equipment with the same rider position and I end a test with this position to make sure very little has changed with the environment over the course of testing.

    As an aerodynamicist, I know the limitations of CFD, where one can "tune" the constants used in the turbulence models (one-equation or two-equation) giving the correct overall drag force, while if you test using pressure taps the pressure field around the cyclist or bike they will not match even closely the numbers found from CFD. This is because highly separated flows such as found with bicycle riders is very difficult to model theoretically and the errors associated with them is high. In addition, the environmental level of turbulence will affect the way the air flows around the cyclist and this is very hard to model adequately. This environmental turbulence will affect where and the mode at which the flow separates from the body (i.e. level of turbulence affects the growth rate of the factors involved with the instability that causes certain types of separation for both laminar and turbulent flow).

    With this said and some reasons why I test as I do, I really value the data I get from my testing program at Hughes Park in Long Beach, California. Some changes I make to the bike are so minute that you can't see whether it works or not based on the error estimates involved with testing. For example, testing with a water bottle on the down tube verses no bottle or cage is very hard to determine at my usual power levels, which is 250W. However, when I test at 300 or 325W, sometimes I can resolve the data to determine whether it worked or not. However, it is much harder to test at 325W for multiple runs, so I use this type of testing only when I determine that at 250W that I'm having difficulty determining whether the change worked.

    I just got my Cannondale Slice RS, so I haven't had much chance to test different positions on it. I've done two TT's of 10 miles at Hughes Park (21:28 at 325W and 21:37 at 327W average) and the only changes I made between the two TT's is for the second one I extended the stem forward one CM and lowered the aero bars 1 CM and adjusted the saddle up to match the road bike's saddle height and changed the saddle angle. I felt comfortable on the bike with the change with the exception that I induced a pressure point in the crotch region that made the ride less than comfortable. The bike came with a Fizik Arione saddle and I'm looking to change it to a TT specific saddle such as a ISM Adamo TT or similar.

    Thank you all for your input and I will definitely keep testing and using your ideas to help me improve.
     
  14. daveryanwyoming

    daveryanwyoming Well-Known Member

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    It sounds like you've got a very good handle on both the theory and field testing side of aero positioning.

    Have you also looked into the functional side of fitting in terms of things like max and min knee and hip angles? I ask because ideally you shouldn't see a big power drop when down in the drops of your road bike and as mentioned above after enough time you should see very little power drop when in your TT bars. Some is normal and as Smaryka points out a bit of power loss that's more than offset by aero gains is a good tradeoff. But I wonder if you're experience with aerodynamics encourages you to tilt that a bit further than most hoping to drop that CdA but compromising your position a bit too much in the process.

    Some good images and references on things like hip and knee angles here: http://bikedynamics.co.uk/FitGuideTT.htm

    FWIW, a lot of folks I've worked with that self fit did fine on saddle height as it relates to knee angles and most arrive at a workable pad height and reach and with it their max hip angle probably isn't too aggressive but many overlook minimum hip angle or angle between torso and femur at the top of the pedal stroke and try to ride crazy tight angles there as in 35 degrees or so because they're riding a very slack road like saddle position or overly long cranks for their torso angle. Those kind of things usually show up as comfort issues or reduced power.

    BTW, you should definitely try something like an Adamo or Cobb saddle for TT positions. It really helps in terms of allowing a lot of anterior pelvic tilt without a lot of discomfort. Cobb also has an incredible 180 day no questions asked money back policy on saddles so it's a very low risk experiment.

    Your power sounds really solid and with your understanding of and attention to aero details I'm guessing you post some pretty impressive TT times or will if you're not already.

    -Dave
     
  15. Johnny Mac

    Johnny Mac New Member

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    Hi Dave and thanks for taking the time to respond. I got a bike fit for my Cannondale Evo last October by a BG fit specialist and it seemed to work great in terms of fatigue resistance on longer rides. Most of the changes he made were to deal with my leg length discrepancy and to insert various wedges and new footbed inserts to deal with my other anatomical issues. I also used the same position the bike fitter found for me on my Cervelo S2 (as much as I could despite some of the components being different. During the fit session, he measured the hip and knee angles and my flexibility and I am beginning to think that at least some of my issues may be related to a lack of flexibility. I need to stretch more and I have had some tight hamstrings over the past few weeks. So maybe once I retain some of that flexibility, I might see some improvement in my cycling.

    With an improvement in flexibility, have you seen substantial improvements in power output or even like in my case an improvement in the power differential between an optimized aero position and say a position on the hoods?
     
  16. daveryanwyoming

    daveryanwyoming Well-Known Member

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    To some extent yes, but flexibility especially hamstring flexibility has a lot more impact on saddle height and how open a max knee angle you can sustain than it does the remainder of your fit. Sure with more flexibility you can typically ride a slightly higher saddle and may be able to tolerate lower bars and a flatter back without as much anterior pelvic tilt. But if you lack that much flexibility the key is to find a fit that works with what you've got. IOW, the fit should match the rider's functional flexibility not the other way around and if you're not flexible enough or get a lot of hamstring soreness after longer or harder rides then I'd drop the saddle a tad and perhaps raise the bars a bit.

    Once you get a solid and functional road bike fit that doesn't leave you sore or with tight hamstrings and one in which you can ride down in the drops for extended periods when it's beneficial to do so without losing too much power you're well on your way to a solid and functional TT fit. Ideally you'll take the primary working angles from your functional road bike fit and rotate the whole thing forward around the bottom bracket to get into your aero position. IOW, the actual angles like max and min knee and hip angles shouldn't really change but with the much lower front end and flatter back you'd get there by steepening up the seat angle (and raising it to give the same knee extension in the steeper position) and lowering the elbow pads.

    The limit to how far you can rotate forward around the bottom bracket is typically determined by saddle comfort and how much anterior pelvic tilt you can manage before it gets too uncomfortable, that's where an Adamo, Cobb or similar saddle can help. If you race under strict UCI rules then that can be another set of limitations on how far you can rotate forward around the BB as you'll be limited in terms of saddle nose setback but again the snub nosed saddles like an Adamo or Cobb can help you get steeper and stay UCI legal. The UCI also limits how far you can stretch forward and most taller riders will end up taking the morphological exception that allows 80cm of reach from the BB center to the end of the aero bar tips.

    So yeah, additional flexibility may help your comfort and power and you may want to work on that, especially in the off season. But ideally a functional fit works from what you are currently capable of handling and doesn't try to force your body into a position that is too aggressive for your current flexibility. That applies to both road and TT fits but if you get the road fit dialed from a functional perspective you can then rotate that position around and forward until you're limited by saddle discomfort (most folks have to consciously work on the anterior pelvic tilt and retrain themselves not to sit bolt upright on the saddle in an aggressive TT position) or limited by UCI regulations if that applies to your racing (it rarely applies in US amateur events outside of national championships or some high profile elite NRC races).

    I can't speak on the quality of your fit, but there are fitters and fitters and it sounds like your fitter at least focused on the cleat and leg length issues which is good but they may or may not have paid enough attention to your overall fit and functional capabilities in the drops which is also part of the deal.

    -Dave
     
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