Using a HRM properly

Discussion in 'Cycling Training' started by Martinp, Jan 28, 2003.

  1. Martinp

    Martinp New Member

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    Ok, I'll readily admit, that despite owning a new HRM for over a year now, I have not really used it, either properly, nor to its full potential.

    I seem to use it merely to confirm what I already know whilst on the bike i.e. I am idling and could go faster or I am breathless and incapable of any more effort.

    I think the best place to start, would be to fully understand the readings obtained. So, the first one that I would welcome opinion on is "KCal".

    This obviously means Kilo Calories and a reading of say, 992 equates to 9920 calories. But what does that mean to a cyclist in training? Should I even be watching this reading? Can I use this reading to help with my current objective to lose 7 kgs?

    Any input welcomed!

    Mutton
     
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  2. ric_stern/RST

    ric_stern/RST New Member

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    Kcal is simply a measure of energy expenditure, and is there to provide an *estimate* of the amount of energy that you have used.

    As the data comes from a HR monitor it's likely going to be wildly inaccurate. To determine energy expenditure correctly, this needs to measured in a lab setting, as expired respiratory gases need to be analysed.

    A good ballpark figure can be obtained for energy expenditure from an accurate power meter (e.g., Power Tap hub, SRM cranks), as power = energy / time. Thus, energy = power x time, giving an answer in kj, which is then divided by 4.18 to get an answer in kcal, with Kcal being the figure that most people use (at least here in the UK).

    Most (all trained, and even most untrained) cyclists fall into ~ 20 - 25% efficient when cycling, such that if you multiply the the above kcal expenditure by ~ 4 you arrive back at the same figure in kcal as kj, i.e., if you have a power meter and it said you expended 1000 kj on your ride, you also expended ~ 1000 kcal (as opposed to 239 kcal).

    To correctly calculate your efficiency, you'd have to be in a lab, and have your expired respiratory gases analyses and have your power accurately determined.

    As an aside your efficiency increases, as your absolute power increases, and your efficiency decreases as your absolute cadence increases.


    Accordingly, the 992kcal your watch measured, 'would be' 992 kj. if for instance that one obtained from one hour of cycling (purely used for illustrative purposes only), you'd have ridden at an average power output of 275.5 W. For an average sized male (~70kg) on a TT bike, on a flat circuit, that would equate to ~ 43 km/hr (as a ballpark figure).

    The energy figure you is unlikely to be accurate. if it was accurate, there'd be no need to have power meters!

    Therefore, i wouldn't base any weight loss plans on this figure as it's likely to be completely erroneous. However, you could use it as some sort of tracking number that you record in a training diary. Assuming that the figure increases (i don't know how they exactly estimate energy expenditure) as you ride at a higher intensity and/or longer volume, you'd be able to see that now you can expend 992 kcal per ride, whereas two months later you might be able to burn 1500 kcal.

    Ric
     
  3. Duckwah

    Duckwah New Member

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    i agree with ricstern, the Kcal measure from a HRM is based on an approximation and will definitely vary from person to person just like Max HR and training zones.

    if you have a look at my other post on HR below you will see that there is a big difference between what is predicted and what a test will show. When i did the test for VO2 etc the calculated my energy expenditure per hour and it was about 20% different to the numbers i was getting from my HR monitor.

    Which HRM do you have and what sort of features does it have? If you can provide details then its easier to give you ideas on how to use your HRM to improve your training.
     
  4. steve

    steve Administrator
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    Ric,

    I've got a polar s710 at the moment and i'm thinking of getting the power sensor add-on, have you used these b4? how do they compare to the power tap setup or an SRM crank?

    thanks!
     
  5. ric_stern/RST

    ric_stern/RST New Member

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    I've never used an S710, so can't comment personally, however, i do know people that have, and the concensus seems to be that (average) power is quite accurate compared to the SRM or Power Tap, but the instantaneous power can be off.

    However, there *appears* to be great problems in setting the unit up, and getting it to give acurate numbers, such that i'm led to believe that to get accuarte figure it may need to be installed concomitantly with an SRM or PT to ensure it's validity.

    Some further info on S710 and power meters in general can be found at http://www.midweekclub.com/powerFAQ.htm

    http://external.nj.nec.com/homepages/sandiway/bike/feather/tt/s710/index.html

    Ric
     
  6. Martinp

    Martinp New Member

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    Duckwah

    I have a Polar S210.

    It has the usual zone settings, OwnIndex, Vo2 Max, Fit Test, Kcal, various exercise settings, OwnMax etc.

    Regards

    Mutton
     
  7. ric_stern/RST

    ric_stern/RST New Member

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    The Vo2max and kcal figures will just be very loose approximations, and are likely to be wildly inaccurate. I don't know what the other settings are.

    The best way to use the monitor is to set up your training level zones, and then maybe just keep a running tally of how long you spend in each zone. anything else with a HR monitor is probably overkill.

    Ric
     
  8. Duckwah

    Duckwah New Member

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    with an S210 you can set up different zones for recovery/long slow distance rides, aerobic training and intervals. The ability to train using time and heart rate based intervals can be useful as well.

    for example when trying to improve your VO2 it is important to do high intensity interval training. To do this, set up your monitor for 6-8 intervals at 85-100% MHR (or whatever your high impact zone is) for 60-120 seconds and then use the recovery based interval function to prompt you to start another interval when your HR drops back into your low intensity zone.

    alternately simply base your intervals on an interval time and recovery time.

    your HR monitor can also be used to check your recovery from exercise oveer the next day and can be used to alert you to times when you should and shouldn't train but really only super srious cyclists worry about that sort of thing
     
  9. Leon

    Leon New Member

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    Steve

    For the answer to your question check out the test done by Adam Hodges Myerson on three different Power Meters including the Polar product.

    All in all the Polar product produced reasonable results although unreliable at low power output.


    The article can be found at

    http://www.monkeyhillcs.com/chung/rosetta/rosetta.html


    There is also some issues to be considered during installation.

    Check out Sandiway Fong's site at:

    http://external.nj.nec.com/homepages/sandiway/bike/feather/tt/s710/index.html

    and Phil Stone's site at:

    http://users.pandora.be/phil.stone/Racing in Belgium/startpage.htm

    I would say that the Polar Calorie measurement is a good relative measure and with a bit of experimenting can be "calibrated" to assist with diet and weight loss.

    I have simply by back analysis established what calorie output I should aim for to reduce weight.


    Cheers

    Leon
     
  10. Ronnie

    Ronnie New Member

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    Mutton

    Polar are holding a workshop in Joburg with the following brief:
    "From the basic foundations of intensity based training, to creating various training sessions and tracking your progress. The workshop is aimed at all heart rate monitor users or potential users looking at getting a better return on their investment. All the way to planning you're training for an event, to tracking your progress then putting it all together with your software."

    Module I: basic concepts and the calculation of target zones, typical training sessions for each target zone as well as how to check your progress.
    Date: Wednesday, 5 February 2003

    Module I is followed by a practical application - on bike or in running shoes using your HRM.
    Date: Wednesday, 12 February 2003

    Module II:
    Planning and periodisation, and use of their Training Planner software
    Date: Wednesday, 19 February 2003

    Contact Polar agents at (011) 805-1028 or email [email protected].

    I am looking forward to getting to know my polar better - perhaps I will see you there.
     
  11. ric_stern/RST

    ric_stern/RST New Member

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    i have a *feeling** that there was something wrong with the SRM, most likely it wasn't calibrated correctly, which would bring the PT and SRM closer together. a few labs and individuals have found that the PT and SRM are within 2 - 2.5% agreement of each other.

    Ric
     
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