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Thread: Explain Pw:HR?

  1. #1
    umd
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    Explain Pw:HR?

    I've read about decoupling, but I can be kind of dense and I don't really get it completely. My numbers can be all over the place, is it really showing me anything about my fitness or is it just noise?

    Edit: here was some data for a climb today...

    Climb:
    Duration: 17:25
    Work: 271 kJ
    TSS: 25.5 (intensity factor 0.938)
    Norm Power: 263
    VI: 1.01
    Pw:HR: 4.8%
    Pa:HR: 15.7%
    Distance: 2.924 mi
    Elevation Gain: 1232 ft
    Elevation Loss: 30 ft
    Grade: 7.8 % (1203 ft)
    Min Max Avg
    Power: 0 456 259 watts
    Heart Rate: 119 185 173 bpm
    Cadence: 55 109 81 rpm
    Speed: 2.3 18.7 10.1 mph
    Pace 3:12 26:06 5:57 min/mi
    Altitude: 196 1398 798 ft
    Crank Torque: 0 584 278 lb-in

    Some SST yesterday

    Entire workout (229 watts):
    Duration: 1:12:02 (1:17:18)
    Work: 992 kJ
    TSS: 90.6 (intensity factor 0.869)
    Norm Power: 243
    VI: 1.06
    Pw:HR: 6.9%
    Pa:HR: -27.48%
    Distance: 24.311 mi
    Elevation Gain: 2076 ft
    Elevation Loss: 2077 ft
    Grade: -0.0 % (-1 ft)
    Min Max Avg
    Power: 0 613 230 watts
    Heart Rate: 55 173 159 bpm
    Cadence: 2 124 94 rpm
    Speed: 0 52.3 20.3 mph
    Pace 1:09 0:00 2:57 min/mi
    Altitude: -14 804 299 ft
    Crank Torque: 0 852 208 lb-in


    And a group ride yesterday

    Entire workout (229 watts):
    Duration: 54:33 (1:01:23)
    Work: 751 kJ
    TSS: 78 (intensity factor 0.926)
    Norm Power: 259
    VI: 1.13
    Pw:HR: 12.58%
    Pa:HR: 5.12%
    Distance: 20.533 mi
    Elevation Gain: 1287 ft
    Elevation Loss: 1297 ft
    Grade: -0.0 % (-10 ft)
    Min Max Avg
    Power: 0 716 230 watts
    Heart Rate: 67 185 163 bpm
    Cadence: 1 121 91 rpm
    Speed: 0.7 50.8 22.7 mph
    Pace 1:11 87:47 2:39 min/mi
    Altitude: 47 250 115 ft
    Crank Torque: 0 785 213 lb-in
    Last edited by umd; 12-03-08 at 04:59 PM.

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    Pedalphile
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    In 2009, USAC will be implementing HR caps so you have to be able to produce the most power for the lowest HR.

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    I am the cheese sgrundy's Avatar
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    umd
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    If you look at my OP you will see that I already linked to that... I read it, I just don't "get it".

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    I am the cheese sgrundy's Avatar
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    Ooops. I don't understand all the math, but the idea is pretty simple as far as I can tell. It draws trend lines for power and heart rate and tracks how much they diverge, which is supposed to be an indicator of aerobic fitness. Seems like bs to me. Either way its practically useless.

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    umd
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    Quote Originally Posted by sgrundy View Post
    Ooops. I don't understand all the math, but the idea is pretty simple as far as I can tell. It draws trend lines for power and heart rate and tracks how much they diverge, which is supposed to be an indicator of aerobic fitness. Seems like bs to me. Either way its practically useless.
    Hehe, no problem. That's what I'm trying to figure out, if it's just BS or at all useful...

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    Senior Member ericm979's Avatar
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    It measures (or tries to measure) cardiac drift. Your HR goes up over time at the same power. It's worse, to the point where I noticed it just from watching the instantaneous numbers on the PM, when I am tired or do a ride that's too long for my current fitness... my power goes down but my HR stays the same.

    The theory is that the more aerobically fit you are the lower the drift. But I am not sure how applicable it is, especially to an entire ride which has hard parts and not so hard parts. It sounds (from posts on Wattage list) like the research is pretty new and there isn't that much out yet.

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    Senior Member tanhalt's Avatar
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    Sheesh. Why are you even wearing a strap?

    Here's my take on it...the article explaining it is written by Joe Friel (i.e not Andy Coggan or Hunter Allen).

    ...'nuff said.

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    umd
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    Quote Originally Posted by tanhalt View Post
    Sheesh. Why are you even wearing a strap?
    I like the support. I'm still used to how it feels

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    Senior Member tanhalt's Avatar
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    Quote Originally Posted by umd View Post
    I like the support. I'm still used to how it feels
    The "support"?? Sounds like you might want to just wear a "Bro" instead

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    umd
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    Quote Originally Posted by tanhalt View Post
    The "support"?? Sounds like you might want to just wear a "Bro" instead

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    Making a kilometer blurry waterrockets's Avatar
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    Quote Originally Posted by ericm979 View Post
    It measures (or tries to measure) cardiac drift. Your HR goes up over time at the same power. It's worse, to the point where I noticed it just from watching the instantaneous numbers on the PM, when I am tired or do a ride that's too long for my current fitness... my power goes down but my HR stays the same.

    The theory is that the more aerobically fit you are the lower the drift. But I am not sure how applicable it is, especially to an entire ride which has hard parts and not so hard parts. It sounds (from posts on Wattage list) like the research is pretty new and there isn't that much out yet.
    Yeah, I tried to dive into it a couple months ago and lost interest quickly. I wore my HR strap for the first time in 6 months on Monday. I think I've already misplaced it again...
    http://groups.google.com/group/watta...rch+this+group

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    Ninja don't wear flipflop king-tony's Avatar
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    I believe that this typically measures aerobic fitness which is 55-75% of ftp. Just glancing at your summaries which you have pasted, it appears that all three of the rides were outside of this range. Additionally, you will notice that there is a correlation between your avg pwer and NP. With the tightest pw:hr your AP/NP was 1.5% for the next tightest it was 5.3% and for the last ride it was 11.2%. This makes sense. On your climb you were certainly pedaling the entire time, probably very smoothly and your power file for this probably looks like a straight line. 17 minutes is not very long so at a constant effort you would see less drift. During the SST ride you were riding at a constant pace, but probably had periods where you had to stop pedaling at intersections etc. During these periods your HR stays higher for a short period at zero power or if you were not holding the power on the back side of rollers you would have lower power to hr numbers. Finally, hydration, nutrition and weather can impact these numbers as well. You could do the same ride at the same average power, but if you do not hydrate you are going to see a higher HR. It is best to compare similar rides and also to look at longer rides where you will experience drift.

    ...at least that is my guess.

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    A more effective way to use it is "how does my heart rate change for a given effort over a given time period?". The calculation is only useful when either power or heart rate are kept at a constant as in a steady state effort. So, for example, if you do 3x6 minutes in zone 3, you can see how your power responded to the constant HR. OR, if you do 3x6 at 89% of FTP, you can see the same thing in reverse.

    However, if you just go out for a random ride of varying efforts you will get very skewed numbers.

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    umd
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    Quote Originally Posted by currand View Post
    A more effective way to use it is "how does my heart rate change for a given effort over a given time period?". The calculation is only useful when either power or heart rate are kept at a constant as in a steady state effort. So, for example, if you do 3x6 minutes in zone 3, you can see how your power responded to the constant HR. OR, if you do 3x6 at 89% of FTP, you can see the same thing in reverse.

    However, if you just go out for a random ride of varying efforts you will get very skewed numbers.
    That makes sense... the first two examples were relatively steady power efforts. The third one was all over the place

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    Quote Originally Posted by The_Cretin View Post
    In 2009, USAC will be implementing HR caps so you have to be able to produce the most power for the lowest HR.
    will these caps be based on Pw:HR, LTHR, MHR, or RHR? Please provide a link, I'm concerned about this because my HR is like a hummingbird's.

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    Quote Originally Posted by MDcatV View Post
    will these caps be based on Pw:HR, LTHR, MHR, or RHR? Please provide a link, I'm concerned about this because my HR is like a hummingbird's.
    It will be based on HR while racing. You have to stay under 180 bpm. Races will no longer be determined by putting out the most power for the same amount of time or the same power for a longer period of time. Thus the importance of working on your power:HR ratio.

    Link:

    USAC to Implement Heartrate Limits in 2009

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    Killing Rabbits
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    Quote Originally Posted by The_Cretin View Post
    Races will no longer be determined by putting out the most power for the same amount of time or the same power for a longer period of time.
    Thanks for that, I mistakenly thought the fastest guy won the race. Hard to keep up with all the rule changes.

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