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2x20 intervals

shockedsoshockedshockedsoshocked Posts: 4,021
Just wondering, what % of lactate threshold, or Max HR, should these be conducted at?
"A cyclist has nothing to lose but his chain"

PTP Runner Up 2015

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  • Gav888Gav888 Posts: 946
    Depends what you are using the 2 x 20 for, most people refer to these types of intervals as threshold intervals and are done - using friel's zones - between 94% and 99% of LTHR. If you want Max HR its between 81% and 90%.
    Cycling never gets any easier, you just go faster - Greg LeMond
  • Cheers Gav,

    My LTHR is bang on 90% of my max, so guess I'll just hit that!
    "A cyclist has nothing to lose but his chain"

    PTP Runner Up 2015
  • BhimaBhima Posts: 2,145
    HR is so slow to respond though - maybe it's ok once you get there but, if you try to hold it, you'll have to back off the power to stop it climbing higher.

    I'm just doing it on feel at the moment and going the hardest I can for the specified duration. Even when going at the same pace for an hour, my HR continues to increase during the recovery period afterwards so my experience of using HR as an indicator of how hard i'm going just seems bizzarre...

    I don't get it. Please enlighten me. How do you use it during intervals? Perhaps there is an effective way of doing it but, as i've only ever used a HR device once or twice, I have no idea how it would work properly. Am I missing out on something by not having any HR gadgets?
  • andyrrandyrr Posts: 1,665
    Increasing HR during steady effort is know as cardiac drift I think. One reason why using HRM to determine your effort is imperfect. Maybe worse with insufficient cooling / dehyrated.
    On my KK turbo I'm using the computer to watch the effort (power level) - without that and using HR I'd becareful not to blindly follow the HR value as that could lead to slight easing off towards the latter stages of a longer effort.
    Alternative is to have a rear wheel speed sensor for your computer - speed never lies !
  • cjcpcjcp Posts: 13,345
    Bhima wrote:
    I'm just doing it on feel at the moment and going the hardest I can for the specified duration.

    +1. I also have a perimeter road in a Park which I can time myself around, so I have an idea of how much effort I'm putting in. I do have a HRM, but I don't use it all the time.
    FCN 2-4.

    "What happens when the hammer goes down, kids?"
    "It stays down, Daddy."
    "Exactly."
  • doyler78doyler78 Posts: 1,951
    Whilst I agree with andyrr I think you should also bear in mind that trying to hit HR targets at the start of an interval can mean you are putting out way too much power at the start for which you will pay later. To counter that simply follow the oft quoted mantra from any tester which is to start conservatively and build into what feels like your sustainable power over a couple of minutes that way you can moderate the worst effects of trying to hit HR targets too soon in a steady state interval.

    Speed is a great proxy for power however your trainer setup must be consistent. Tyre pressure should be the same session to sessioni and a roll down test conducted to ensure consistency. Speed gives you a measurable metric by which you can objectively judge changes in your power.
  • Bhima wrote:
    HR is so slow to respond though - maybe it's ok once you get there but, if you try to hold it, you'll have to back off the power to stop it climbing higher.

    I'm just doing it on feel at the moment and going the hardest I can for the specified duration. Even when going at the same pace for an hour, my HR continues to increase during the recovery period afterwards so my experience of using HR as an indicator of how hard i'm going just seems bizzarre...

    I don't get it. Please enlighten me. How do you use it during intervals? Perhaps there is an effective way of doing it but, as i've only ever used a HR device once or twice, I have no idea how it would work properly. Am I missing out on something by not having any HR gadgets?

    Like you said, HR does drift upwards, so after a warm up I find a pace that would hit my 90% at the start of the intervals, then effectively disregard it for the rest of the time I'm doing the interval. I mainly use it on the turbo so I know I'm going hard enough, and on the road so I don't go too hard (yet!)
    "A cyclist has nothing to lose but his chain"

    PTP Runner Up 2015
  • I try to do 2 X 20 min sessions but have never managed it. I try to keep a steady modest 180 watt (not sure of the accuracy) but after 10 mins my BPM has increased from 80% to 95% of MHR and I have to ease off is this just an indication of unfitness?
  • Old Tuggo wrote:
    I try to do 2 X 20 min sessions but have never managed it. I try to keep a steady modest 180 watt (not sure of the accuracy) but after 10 mins my BPM has increased from 80% to 95% of MHR and I have to ease off is this just an indication of unfitness?
    Just means 180W (as shown by whatever device you are using) is too high. Drop the power to a level that means you can complete the intervals. If it becomes too "easy", then lift the power next time. If it's inconsistent, then maybe your power measuring device is not reliable.
  • chrisw12chrisw12 Posts: 1,246
    Tuggo. I was in the same boat, I couldn't complete them due to pure boredom. Then due to one of the sufferfest vids I ended up doing one using an over, under approach and they were much more tolerable, in fact quite enjoyable.

    What I mean is, say I was targeting 180w, I'd do the first min @160 then 2nd min @200w. and repeat for 20 min,

    This is perhaps a slightly harded way of doing them and given what Alex said perhaps set your target a bit lower and build over the weeks.

    Hope this helps.
  • Thanks for your advice fellas. I thought I should be able to do the 180w easily but I can just manage 2x10mins however this always brings me over 90% MHR which I assume is too high for this time of the year. I should point out that I supplement this once per week turbo session with steady weekend rides - weather permitting. I will try the under and over approach to see if it makes the sessions more bearable.
  • Sorry for hijacking this thread but I did my first set of intervals today and I'm not really sure if the format I used was suitable.

    I had a five minute break between the two twenty minute sessions, with a five minute cool down and was averaging about 85% MHR. Does this sound OK? I know heart rate isn't ideal but it's all I've got at the moment and it being my first interval attempt I couldn't really go on feel alone.
  • Totally agree on the HR monitor being inaccurate, especially indoors. On my turbo rig, if I do a 2x20min's interval at threshold, 350-360W, my HR can be as much as 10-15bpm below my normal LT HR, depending on how fresh I am. By the end of the intervals, it has usually creeped up to the normal LT HR. Fatigue level will play a big part in this - with fresh legs (i.e after recovery days), HR will respond much faster.
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