Sprinting -- what am I doing wrong?
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  1. #1
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    Question Sprinting -- what am I doing wrong?

    I'm talking indoors here, on the Kickr, and racing on Zwift (I don't do outside much at all anymore, so don't ask for comparisons with real world).

    Each race comes down to a sprint finish, and I get my arse jacked every time. It's getting old quick. I don't know what's wrong, whether it's me or the trainer, but each dash for the line I hop up out of the saddle and there is that initial spike of power, but very quickly (even though my cadence is increasing) that power drops of dramatically, sometimes by as much as 200 or so watts.

    If I look at the analysis of my ride data (see below), and focus in on the final sprint, it looks like a right angle tool: nearly straight on front end and falling steadily off as I go. I look at the Strava data of other riders and their sprints are consistent from start to finish.

    Is this a calibration issue?

    https://www.strava.com/activities/2349215965

  2. #2
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    Looks to me like the grade changes from positive to negative and your cadence stays the same so the power should drop off some. Also, you ramp up the speed at the start of the sprint quite a bit then once you are done ramping up your cadence seems it should drop off some because you aren't accelerating as much anymore. Seems like a realistic experience and performance maybe.
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  3. #3
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    Quote Originally Posted by Srode View Post
    Looks to me like the grade changes from positive to negative and your cadence stays the same so the power should drop off some. Also, you ramp up the speed at the start of the sprint quite a bit then once you are done ramping up your cadence seems it should drop off some because you aren't accelerating as much anymore. Seems like a realistic experience and performance maybe.
    I also wonder how much wheel-sucking the faster sprinters comes into play; could be the more ground I gain on them, the more draft effect I'm getting, and thus the lower power output.

    This is the reason I ask questions. I just don't have much of a clue.

  4. #4
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    Drafting matters in Zwift, could definitely contribute if you get on a rider's wheel.
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  5. #5
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    Quote Originally Posted by Wood Devil View Post
    I'm talking indoors here, on the Kickr, and racing on Zwift (I don't do outside much at all anymore, so don't ask for comparisons with real world).

    Each race comes down to a sprint finish, and I get my arse jacked every time. It's getting old quick. I don't know what's wrong, whether it's me or the trainer, but each dash for the line I hop up out of the saddle and there is that initial spike of power, but very quickly (even though my cadence is increasing) that power drops of dramatically, sometimes by as much as 200 or so watts.

    If I look at the analysis of my ride data (see below), and focus in on the final sprint, it looks like a right angle tool: nearly straight on front end and falling steadily off as I go. I look at the Strava data of other riders and their sprints are consistent from start to finish.

    Is this a calibration issue?

    https://www.strava.com/activities/2349215965
    Could it be the initial acceleration is almost all fast twitch, but after a few seconds it can't be maintained and the slow twitch comes into play? Just a thought.

    Next time, start moderately and steadily increase effort, so the watts readings peak [or stay the same] just before the end of the sprint. I believe that's how sprinters do it on TV.

  6. #6
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    Quote Originally Posted by Wood Devil View Post
    Is this a calibration issue?
    Maybe you just suck at sprinting. NTTAWWT.

    Do you do well in sprints on the road?
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  7. #7
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    Quote Originally Posted by QuiQuaeQuod View Post
    Maybe you just suck at sprinting. NTTAWWT.

    Do you do well in sprints on the road?
    I've been run over twice -- I really don't do the outside thing much at all anymore, too many distracted idiots on the road, so I have no great real world comparison. That said, I'm not a fast-twitch guy. I do all right (usually up to around 11-12w/kg on a good day), but I'm never going to be able to compete against the true sprinters. My problem is that I want to find out why the power spikes up on my Kicker but then drops off dramatically after a couple seconds even though I'm in 52-12/13 and with a steady or increasing cadence.

    I'm wondering if I should throw my Vector pedals and see if that makes a difference.

  8. #8
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    Quote Originally Posted by Wood Devil View Post
    I've been run over twice -- I really don't do the outside thing much at all anymore, too many distracted idiots on the road, so I have no great real world comparison. That said, I'm not a fast-twitch guy. I do all right (usually up to around 11-12w/kg on a good day), but I'm never going to be able to compete against the true sprinters. My problem is that I want to find out why the power spikes up on my Kicker but then drops off dramatically after a couple seconds even though I'm in 52-12/13 and with a steady or increasing cadence.

    I'm wondering if I should throw my Vector pedals and see if that makes a difference.
    Read years ago that most riders have their top acceleration drop off after 40 crank revolutions-there was a tip to ride back from the finish line counting off rpms in your preferred sprint gear and note a landmark where you'll go all out.

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    Quote Originally Posted by Bremerradkurier View Post
    Read years ago that most riders have their top acceleration drop off after 40 crank revolutions-there was a tip to ride back from the finish line counting off rpms in your preferred sprint gear and note a landmark where you'll go all out.
    That's good advice! Perhaps a new tactic of max seated cadence to keep on the wheels until it's time to drop to the sprint gear and get out of the saddle.

  10. #10
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    A couple of things make a big difference when sprinting on Zwift.

    1. How you have the Erg mode set up … more toward the middle (steady power regardless of climb or flats), or more toward real, outside riding.
    2. Drafting makes a big difference in sprinting on Zwift
    3. Power ups make a big difference on Zwift … the "Draft" power up is better in a group, the "Aero" power up is better solo
    4. Where you start your sprint makes a difference … build up and save max effort for the end, drafting to build speed up to that point

    I find very little difference in power between Zwift and the road when sprinting … but suggest a little larger gearing on Zwift than the road. I've hit 1300 watts for 5 seconds and 1000 watts for 23 seconds on Zwift, which is very similar to on the road power (Max power is within 50 watts or so) … using a 1st gen Wahoo Kickr.
    Snakebit: "How many times do I have to tell you that I don't have a source? I don't make a note of everything I see or hear on the internet and you don't have to take my word for it."

  11. #11
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    Quote Originally Posted by Wood Devil View Post
    I've been run over twice -- I really don't do the outside thing much at all anymore, too many distracted idiots on the road, so I have no great real world comparison.
    Maybe this is why you have been run over twice? This from a post you started back in 2011.

    “Cool Drafting Garbage Trucks and Cutting off Cruisers
    It was an eventful ride today. The legs felt good after a day off, and I was really riding hell for leather, banging gears and really screaming along.
    At one point I raced up to a garbage truck that was leaving a stop sign. I caught up and got in his draft and was cruising comfortably along at about 30 or so for a couple miles. And later I flew around a rotary and drafted a cop car for a bit (foolish, I know, but I was feeling good) and stopped behind him in traffic as we both waited to take a left. I was doing that upright balance thing, trying not to unclip, and got a bit inpatient as I was about to fall over. So I darted off when I had the chance. The cop obviously saw me behind him and knew what I was doing, so he sort of threw a block for me while I cut in front.”




    Sounds like an accident just waiting to happen to me?
    Last edited by bmach; 4 Weeks Ago at 07:52 AM.

  12. #12
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    Quote Originally Posted by Wookiebiker View Post
    A couple of things make a big difference when sprinting on Zwift.

    1. How you have the Erg mode set up … more toward the middle (steady power regardless of climb or flats), or more toward real, outside riding.
    2. Drafting makes a big difference in sprinting on Zwift
    3. Power ups make a big difference on Zwift … the "Draft" power up is better in a group, the "Aero" power up is better solo
    4. Where you start your sprint makes a difference … build up and save max effort for the end, drafting to build speed up to that point

    I find very little difference in power between Zwift and the road when sprinting … but suggest a little larger gearing on Zwift than the road. I've hit 1300 watts for 5 seconds and 1000 watts for 23 seconds on Zwift, which is very similar to on the road power (Max power is within 50 watts or so) … using a 1st gen Wahoo Kickr.
    So what do you have the in-game resistance set at? Zwift sets it automatically at 50%, but I find I get better out-of-saddle climbing performance when nudge it up bit. I've heard that 100% leaves you spinning on the descents while those that have the resistance lower pull away from you because they are able to maintain consistent power.

  13. #13
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    Quote Originally Posted by Wood Devil View Post
    So what do you have the in-game resistance set at? Zwift sets it automatically at 50%, but I find I get better out-of-saddle climbing performance when nudge it up bit. I've heard that 100% leaves you spinning on the descents while those that have the resistance lower pull away from you because they are able to maintain consistent power.
    I run mine at 80% ... that gives me better road feel with a fair amount of resistance on the climbs, but still a little on the downhills. Most that race run it in the 50%-60% range and turn them into TT's with a sprint at the end.

    For racing, if you are at 50%, bump it to 60% ... if you are still struggling, move it to 70% and see how that goes. Eventually you will find a range you are happy with.
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  14. #14
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    Quote Originally Posted by Wood Devil View Post
    That's good advice! Perhaps a new tactic of max seated cadence to keep on the wheels until it's time to drop to the sprint gear and get out of the saddle.
    Watch races. Note just how many seconds the winning sprinters are off the saddle. It's not many, and those are pros.

    Just watched a few on youtube, and the winner will make the final jump about 15 seconds out from the line. Sometimes less, sometimes more, but often that's the time frame. Granted I only watched a highlight reel, and counted it out (not using a timer) but that's in the neighborhood.

    Max time, maybe 30 seconds and then even the best on their best day will blow up.

    Also, laying down power when sprinting out of the saddle takes practice. Practice using leverage to wind up, practice at VERY high RPMs to keep laying the power down in your top gear for the last few seconds. At what RPM does your spin fall apart when in the saddle? When standing? Whatever they are, they could be higher.

    Do you practice sprints? If you want to get better, you should.

    You can also train for sprints, if it matters to you that much. I wouldn't suggest it though, but practice? Yeah, get your form, get your timing, and have fun with it.
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  15. #15
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    Quote Originally Posted by Wookiebiker View Post
    I run mine at 80% ... that gives me better road feel with a fair amount of resistance on the climbs, but still a little on the downhills. Most that race run it in the 50%-60% range and turn them into TT's with a sprint at the end.

    For racing, if you are at 50%, bump it to 60% ... if you are still struggling, move it to 70% and see how that goes. Eventually you will find a range you are happy with.
    That's pretty much where I'm at now -- 60 - 75%.

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