4000 watts...... well yes.....

Discussion in 'Power Training' started by velomanct, Apr 2, 2010.

  1. velomanct

    velomanct New Member

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    Take a top level track sprinter. They produce likely over 2000 watts for a couple seconds. But is that their true power output, when you closely analyze it down to the fractions of a second?

    Nope!

    Using the data shown from Metrigear on this link, you can see that true peak watts are about double the actual displayed watts. Well, we kind of already knew that.

    http://www.metrigear.com/2010/02/26/the-cyclist-as-a-two-cylinder-two-stroke-engine/

    But it's still cool to think that for a fraction of a second, one leg is producing ~4000 watts. Pretty sick stuff.


    I remember reading about olympic weight lifters producing upwards of 5000watts during the fastest portion of a clean. And that's with using 100% of both legs (and body of course).


    I SOOOOO want to get a MetriGear. I'm going to go crazy over analyzing with that :eek:
     
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  2. iliveonnitro

    iliveonnitro New Member

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    Looking forward to the weight lifting argument, now.
     
  3. velomanct

    velomanct New Member

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    I actually may have to alter my stance on that weight lifting arguement. I still don't support it for normal road cycling.

    But since I essentially stopped resistence training, I feel a little weaker (upper body especially), and my peak power is 5-8% lower. I did get sick for two weeks, which wrecked me and set me back, lost a few lbs then too.
     
  4. 886014

    886014 New Member

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    I'm not sure I can agree with your conclusion sorry. Looking at that graph it looks, to me at least, like somebody with a REALLY bad pedal stroke. As for sprinters, well let's just say pedal straps aren't there for laughs :)

    The measuring equipment used in this case looks interesting, however there is already equipment capable of measuring relative power output between L/R legs. It's something that's good to know and work on, I remember being quite surprised for example when I first saw that I am very much left leg dominant.

    If this is something you're interested in I'd suggest saving your money and buying a set of rollers. Not fancy, no flashing lights ... no marketing department behind it either. Yet rollers are a tried and proven way of improving a person's pedal stroke and you can often see the difference just by looking at somebody who has spent a lot of time on the track/rollers.
     
  5. jollyrogers

    jollyrogers New Member

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    Define what you mean by "bad pedal stroke" please.
     
  6. daveryanwyoming

    daveryanwyoming Well-Known Member

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    I had the same thought. Those metrigear plots show exactly what others have shown before, good cyclists don't 'spin' the way most folks think they do. Robert has posted this one a few times and it's very typical of the forces involved in pedaling:

    http://anonymous.coward.free.fr/rbr/kautz.png

    Metrigear's '2-stroke' plot just shows the same thing for both pedals simultaneously.

    -Dave
     
  7. velomanct

    velomanct New Member

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    I know I pull up hard during sprints, because I often chirp the rear tire on those hill accelerations. The only way I'd be able to do that is due to my upstroke unweighting the rear tire for a split second.

    but my form is not pretty, so I assume. My pedal stroke is, I'm quite sure, very choppy. I don't really care as long as I'm producing my highest power possible.
     
  8. 886014

    886014 New Member

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    What I mean is the rider has an extremely inefficient pedal stroke. The plot was very small, but that's the way it looks on my screen. My first hand experience with this was with Polar and with real-time feedback it's very interesting to actually work on pedalling efficiency and see the numbers slowly but surely creep up. You're quite right, most people don't "spin" the way they think they do. Most people aren't top level track sprinters either, which was who the OP was referring to.

    A top level cyclist may not necessarily achieve higher average power just by an increase in peak power, it can also be achieved by increasing the relative duration that crank torque is applied. Looking at the graph provided, at the 6/12 o'clock position absolutely zero watts are being produced and I would suggest that would not be the situation for a top level cyclist. Even on rollers it would be a very choppy action you'd definitely feel. The black line they refer to as "average" is clearly smoothed. In other words I personally don't feel it is valid to extrapolate this data out to a top level cyclist and come to the conclusion of the OP.

    Just my 2 cents.
     
  9. Alex Simmons

    Alex Simmons Member

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    You are right, it isn't the case for top level cyclists, who in fact sometimes display a negative torque during parts of a pedal stroke. Yet they produce the most most power.

    It is the top level cyclists who display the greatest variation in torque applied around the pedal stroke. Those that produce less power have, on average, a "rounder" torque profile.

    It's all about the down stroke.
    Hard and often.

    Also people confuse "smooth pedaling" (i.e. someone that displays a fluid pedaling technique) with the notion that they are pedaling with a "rounder" torque profile. The two are not the same thing.
     
  10. 886014

    886014 New Member

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    Yes but the graph wasn't for a 2000 W sprinter, it was at 400 W, not exactly up there in power terms. I maintain that a top level (road) cyclist will not have a torque plot that looks like this, not at this sort of power, but you're quite right Alex and stand corrected for implying that would apply to top sprinters who do indeed do it "hard and often" ;)

    Edit: I'd be very keen to see results you may have come across regarding track sprinters as I know track is more your interest
     
  11. daveryanwyoming

    daveryanwyoming Well-Known Member

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    I'm certain Alex is actually talking about road and track cyclists generating power closer to FTP, not sprinters generating kilowatts.

    Take a look at Coyle's 1991 study on biomechanical efficiency based on work with state and national level time trialists: http://www.midweekclub.ca/articles/coyle91.pdf

    In particular take a look at the pedal force curves presented in the paper including this one that compares elite time trial riders (40K time < 56 minutes) to state level time trial riders and the torque they generated during different phases of the pedal stroke while riding at their 40K power (FTP). The elite riders pushed harder on the downstroke but with less of a 'round' pedal stroke and generated a pattern very similar to what you're asserting constitutes poor pedaling style.

    As choppy as these graphs look, they actually represent very good pedaling style if your goal is to go faster. It's just that most folks haven't actually seen accurate high sample rate torque curves plotted against the phase of the pedal stroke and the myths of scraping mud and spinning circles die hard.

    -Dave
     
  12. 886014

    886014 New Member

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    Thanks very much Dave, I hadn't seen that particular study. At this stage I've only read the abstract and skimmed the body, but would but it certainly seems to fly in the face of some other studies and I very keen to print it off and read it through thoroughly a few times. I noted the sample size is very small, but I guess that's pretty much what you're stuck with amongst this population.

    The relative unimportance of the upstroke is, I think pretty well accepted by most, however from what I've read the authors are suggesting peak torque output is THE most important factor, which is extremely interesting, to say the least! Plots I'd seen prior to those provided here showed a somewhat different shape to the bell curve between cyclists, with those considered to have a "smooth" style having a broader curve. In other words torque was introduced earlier in the crank cycle and maintained for longer (ie colloquially "kick and pull") Edit: sorry to avoid confusion substitute "pull" for "scrape". I think of it personally as pulling through the bottom of the cycle, but don't want to imply "pull" as in pulling up.

    Does that imply drills and techniques to improve this area (eg one legged cycling, rollers, electronic feedback) have no value?

    Edit: This study is pretty well known I think and suggests cycling efficiency is indeed important, sorry I only have an abstract http://www.ncbi.nlm.nih.gov/pubmed/12471319
     
  13. daveryanwyoming

    daveryanwyoming Well-Known Member

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    There are many of us that think so and don't do any one legged drills, don't pay any attention to spinscan numbers, 'scraping mud' while pedaling or other related stuff but there are still lots of cyclists that are deeply committed to 'improving' their pedal stroke whether or not there's any evidence that it will make them faster.

    I've read that abstract before and don't find it surprising in terms of GME and CE but have never seen the full text. Did they use force measuring pedals and if so what did they show in terms of force application vs pedaling phase?

    Don't assume that the term 'Cycling Efficiency' as used in exercise physiology papers means the same as 'efficient pedaling' which is what many advocates of spinning circles and mud scraping say will come from such drills. In the Coyle paper I linked they use a similar term "Cycling Economy' which is just the ratio of power generated at a sub maximal workload (FTP) to the VO2 gas exchange rate for each athlete at that same workload. IOW, it's a term that effectively shows the percentage of power each cyclist can deliver through the pedals vs. the theoretical power they should be able to extract by burning fuels at their particular VO2 exchange rate. A lot of things go into that 'efficiency' term, the big one being Gross Metabolic Efficiency which for most folks ranges from about 20-26% and just tells us how much useful energy we can deliver while combusting fuels and how much is burned off as waste heat (roughly 77% gets burned off as heat on the average, no wonder we get so hot on the indoor trainer while pumping out 300 watts and having to dissipate over 900 as waste heat).

    The point is that the lay use of the term 'efficiency' and the technical definition are not in general the same. So if you're reading too much into abstracts like the one you linked and they didn't actually explore torque application around the pedal stroke then it's not really relevant to this topic.

    -Dave
     
  14. 886014

    886014 New Member

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    Dave I don't recall off the top of my head, and would probably have to crawl through the bowels of my roof to answer your question. I will confess I do remember it being somewhat controversial however.

    Regarding abstracts, it's always important to read the full text of a paper before determining whether the paper is relevant to one's application of interest. I have a book on my shelf (that will remain nameless to protect the guilty) on power training and I am quite certain the particular author has not actually read even one full paper. It's full of citations to published studies and certainly sounds impressive, but as I was reading through it I thought "hang on, I remember that study ...."
     
  15. taricha

    taricha New Member

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