Large increase in heart rate for same power as workout progresses

My heart rate increased dramatically over the course of an aerobic workout with a fairly consistent power profile and I would like to know what others think. Here is some data...

Workout duration = 90 minutes

Full ride average power = 59 watts with 126 bpm average heart rate
First half average power = 57 watts / 116 bpm
Second half average power = 61 watts / 136 bpm
Final third = 59 watts / 139 bpm
Final ten minutes = 65 watts / 146 bpm

Some example interval data points...

33 minutes in there was a two minute interval at 76 watts with an average heart rate of 127 bpm

At 1:13 there was another 76 watt interval at 140 bpm
...followed by a 64 watt interval at 144 bpm
...followed by another 76 watt interval at 148 bpm
...followed by a 71 watt interval at 149 bpm
...etc

For context, I have only been on the bike since mid-December after being off the bike for more than 10 years.

Also, this is my longest ride since then with my other rides being <= 60 minutes.

The first half of the ride was mind-numbingly boring while the final part of the ride was very difficult with a much higher RPE.

If I had to guess, I'd say that I simply had to work harder as the workout progressed because I haven't developed any stamina yet.

Am I right?

Comments

  • imposter2.0
    imposter2.0 Posts: 12,028
    Might be something as simple as cardiac drift - can be influenced by many internal/external factors. What are those HR numbers in terms of %max?
  • cougie
    cougie Posts: 22,512
    It's not that dramatic. So your HR was higher for the same watts as the workout went on ? I'd expect it to be.
  • Hydration, fatigue level, plus a score of other factors will be the reason for this.
  • diy
    diy Posts: 6,473
    The body has to work harder to create energy once the glycogen has gone. But I doubt that is the reason. I suspect the efficiency and quality of pedal stroke has dropped off, meaning more energy needed for the same power output.
  • VamP
    VamP Posts: 674
    How are you measuring power and HR? I ask as those power numbers are (impossibly) low and unlikely to be a result of accurate measurement.

    Otherwise GIGO applies.
  • Imposter wrote:
    Might be something as simple as cardiac drift - can be influenced by many internal/external factors. What are those HR numbers in terms of %max?

    Here is average heart rate labeled as percent max and binned by watts and time in seconds.

    http://www.mediafire.com/convkey/9d35/u ... 47cwzg.jpg
  • Hydration, fatigue level, plus a score of other factors will be the reason for this.

    Good points and I forgot to add that this is my first morning workout and I also did it fasting. I also drank water before and after but I wonder now how it's possible to be sufficiently hydrated in the morning?
  • diy wrote:
    The body has to work harder to create energy once the glycogen has gone. But I doubt that is the reason. I suspect the efficiency and quality of pedal stroke has dropped off, meaning more energy needed for the same power output.

    I did do this workout fasting, in a fasted state, or however you say that.
  • VamP wrote:
    How are you measuring power and HR? I ask as those power numbers are (impossibly) low and unlikely to be a result of accurate measurement.

    Otherwise GIGO applies.

    I'm breaking barriers with respect to weakness I guess. The numbers are from Kickr Snap and I believe they are accurate. If you think my power if low, you definitely don't want to see my watt/kg!
  • Thanks everyone for the responses. I have another, shorter workout tomorrow morning so I'll see how I do...
  • VamP
    VamP Posts: 674
    VamP wrote:
    How are you measuring power and HR? I ask as those power numbers are (impossibly) low and unlikely to be a result of accurate measurement.

    Otherwise GIGO applies.

    I'm breaking barriers with respect to weakness I guess. The numbers are from Kickr Snap and I believe they are accurate. If you think my power if low, you definitely don't want to see my watt/kg!


    I still think your numbers are out. I'd recommend borrowing a power meter and running some calibration tests.
  • VamP wrote:
    VamP wrote:
    How are you measuring power and HR? I ask as those power numbers are (impossibly) low and unlikely to be a result of accurate measurement.

    Otherwise GIGO applies.

    I'm breaking barriers with respect to weakness I guess. The numbers are from Kickr Snap and I believe they are accurate. If you think my power if low, you definitely don't want to see my watt/kg!


    I still think your numbers are out. I'd recommend borrowing a power meter and running some calibration tests.

    OK will do.
  • svetty
    svetty Posts: 1,904
    ....The numbers are from Kickr Snap ...
    Turbo-training gets you pretty warm - part of the HR rise might be due to over-heating. Most people need a big fan to keep cool on a turbo....
    FFS! Harden up and grow a pair :D
  • Firstly, those power numbers are incredibly low and I’d be sceptical that they’re right.

    Secondly, it’s normal for heart rate to rise relative to power. I notice it much more indoors as the thermal stress takes effect. Google aerobic decoupling.
  • Svetty wrote:
    ....The numbers are from Kickr Snap ...
    Turbo-training gets you pretty warm - part of the HR rise might be due to over-heating. Most people need a big fan to keep cool on a turbo....

    Makes sense. I'll get a bigger fan. Thanks.
  • Yanis Nayu wrote:
    Firstly, those power numbers are incredibly low and I’d be sceptical that they’re right.

    Secondly, it’s normal for heart rate to rise relative to power. I notice it much more indoors as the thermal stress takes effect. Google aerobic decoupling.

    Well I hope you're right about my power being higher! I'll be disappointed if they end up being correct. If I can an on-bike power meter it'll be interesting to see what it says. I can say that I know that my tire is not tight enough on the roller because my spindown time is above what it should be but I've been keeping it consistent so numbers are consistent. I'll be sure to do it correctly prior to my next test.
  • hdow
    hdow Posts: 184
    Quite simple. You are not aerobically very fit yet. Training since mid December (5 weeks?) and increased ride from 60 to 90min. Your HR per Watt increased by 9% in the second half, more than 5% shows aerobic decoupling - i.e. you need more aerobic fitness for that duration or intensity. So keep doing what you are doing and that decoupling will reduce.
  • Hdow wrote:
    Quite simple. You are not aerobically very fit yet. Training since mid December (5 weeks?) and increased ride from 60 to 90min. Your HR per Watt increased by 9% in the second half, more than 5% shows aerobic decoupling - i.e. you need more aerobic fitness for that duration or intensity. So keep doing what you are doing and that decoupling will reduce.

    Makes sense. Thanks!
  • Ride too much and probability of decoupling definitely goes up. Unless the other half rides too.