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Lactate Threshold Guided Test - Questions...

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  • Lactate Threshold Guided Test - Questions...

    I've been very interested in using my LT for my target heart rates for a while, and recently learned that I needed to take the LT Guided Test on my 645M before that would be possible. I prefer treadmill running as I'm getting older and it's more forgiving on my knees lately.

    Let me back up a slight bit. I am 45 years old, and 200#. I run 2-3 times a week, usually 3.5 miles. Generally, I push my runs during the last mile and get a max heart rate around 165-171 (I'm using a HRM-Run and that's the highest I have ever achieved since using this FR and HRM). I tend to maintain a 8:15-9:00 minute mile; so I'm no Iron Man, but I'm not a couch potato either.

    Twice I have tried to do the LTGT and failed to get a measurable LT. I guess you could say that my failure to read the instructions contributed to my failure to get a LT, but I'm not so sure.

    Here's what happened. It was a cold (I live in Alaska) drizzling rain, with periods of showers and I knew from previous attempts that the LTGT should take about 20-30 minutes. No problem! So I started the Run feature and selected LTGT, hitting OK but not really reading what I needed to do. The clock started with "Warm Up". 20 minutes, still warm up; 30 minutes, still warm up. WTH?! 4 miles into my run and I haven't entered the test yet. I'm now soaked, I can't feel my hands, my calves are smoked because I was keeping my pace above normal trying to get past my "warm up" stage.

    So I ended the run and started walking to recover some. I was really frustrated, and restarted the LTGT to see what I missed. After actually reading the screens, I see that I needed to hit the Lap button to actually start the test!!!! OK, no problem, I can do this now.

    I started the test again, and maintained a pace to stay in the requested zones for the required time, but then it told me to get my heart rate to 175-188 for three minutes!!! I increased my pace even more, I believe I actually hit a 6:00 mile for a brief amount of time, but couldn't maintain that for too long. I was going ALL OUT, and I had no more to give. My max HR was 165 for the entire 2 miles it took me to do the test (after a 4 mile run immediately prior to this). At the completion of the test the watch told me Failed to Reach LT.

    What did I do wrong? My GC heart rate zones are set to default (220-age equation) and I regularly enter Zone 4 when working out, but I can't remember entering Zone 5. Can anyone help me figure out how to finish this test successfully without having a heart attack on the side of the road?

  • #2
    I think you have given the answer yourself: Your max. heart rate doesn't fit the 220-age equation.

    So set your max. heart rate to a lower value which you believe is somewhat true and do the test again.

    Edit:
    I had a closer look at your numbers and something is wrong.

    You say you are 45 years old, and the watch has used the 220-age formula to find your max. heart rate. That would result in a max. heart rate of 175.

    But the watch asked you to run for 3 minutes at 175-188, which is 0-13 BPM above your assumed max. heart rate. That doesn't make sense.
    Last edited by AllanOlesen67; 06-05-2018, 01:41 PM.

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    • #3
      Originally posted by AllanOlesen67 View Post
      I think you have given the answer yourself: Your max. heart rate doesn't fit the 220-age equation.

      So set your max. heart rate to a lower value which you believe is somewhat true and do the test again.

      Edit:
      I had a closer look at your numbers and something is wrong.

      You say you are 45 years old, and the watch has used the 220-age formula to find your max. heart rate. That would result in a max. heart rate of 175.

      But the watch asked you to run for 3 minutes at 175-188, which is 0-13 BPM above your assumed max. heart rate. That doesn't make sense.
      But wouldn't I risk getting a LT which was too low if I set my Max HR around 170-175?

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      • #4
        What the Firstbeat algorithm does is looking at your heart rate variability - the "unevenness" of the time between each heart beat. When you reach your lactate threshold, this variability will change.

        I guess that similar changes in variability are actually also happening at other heart rates. So to prevent any "false positives", the algorithm will probably only search for this behaviour inside a somewhat narrow HR window where it expects to find the lactate threshold. Your lactate threshold is related to your max. heart rate, so the Firstbeat algorithm will probably define this search window based on your max. heart rate.

        Yes, the above contains a lot of "probably" and "I guess". If you are lucky, HermanB from Firstbeat will jump in and give better answers.

        Anyway, I can't see how you would risk getting a too low LTHR by setting the max. heart rate to a value which is realistic for you. To the contrary, you should get a better chance of finding your real LTHR.
        Last edited by AllanOlesen67; 06-06-2018, 11:01 AM.

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