Doubts on lactate test results

  • Creator
    Topic
  • #34015

    Ewa
    Participant

    Hi, I did lactate test last week and have some doubts about the results. The protocol was following: 10’ warmup, walking on treadmill will incline 3-6% with HR around 120. Then stop, first lactate sample and start of the test from walking 3 km/h on incline 15%. Then every 2′ speed was increased by 0.4 km/h.

    We agreed to break the test somewhere above what I felt like anaerobic threshold, not to total exhaustion, and we did so.

    I attached a graph of HR and lactate levels. I received interpretation that my AeT is at 154 bpm and AnT is 172 bpm.

    I may agree with the latter, although the inflection point looks rather to be at 174 but I have doubts about aerobic threshold: at HR=154 bpm lactate level is 1.75 nmol/l, whereas the value 2 is reached for HR around 161-162. I did not feel anything special around 154, but I felt something around 162-163, I could sustain nose breathing until HR 163-165 and speak full sentences to a lab guy.

    I would say my AeT was closer to 162 bom, what do you think?


  • Participant
    Ewa on #34016

    Trying to attach a graph.

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    Keymaster
    Scott Johnston on #34023

    Ewa:

    There are a number of ways to define AeT using blood lactate. One is to call it at 2mMol/L. Another is to call it where lactate levels have risen 1mMol/l above the lowest reading you have seen early in the test. If you get good correlation between lactate levels and ventilation (rate and depth of breathing) then that’s where you want to call it. Since you were just over 2mMol/L at the upper limit of conversation I would call 162 a good choice.

    I hope this helps,
    Scott


    Keymaster
    Scott Semple on #34086

    Either way, I’m curious about their method.

    It looks like they’re drawing a line tangent to the ~4mM mark and then a parallel line to that through your peak lactate. Coincidentally, that parallel line also intersects the 1.75 mM mark.

    Did they explain their method at all?


    Participant
    Ewa on #34093

    Thank you. I fitted a curve to lactate results, read time for which lactate level given by the fitted curve is equal 2 for AeT and 4 for AnT. Then I read interpolated HR values for the calculated time and received 160 and 172 correspondingly.

    I also checked another method of calculating AnT point the intersection of two tangent to lactate graph lines (taken when the graph is more or less linear, a method from lactate.com) and also received 172.


    Participant
    Ewa on #34094

    Scott Semple, yes, it also looks strange to me. It highly relies on maximum HR that I did not reached, missed by a few bpms.
    I looked at methods at lactate.com now I am reading scientific papers on that. Maybe later I will call the lab and ask.

    Later in the skimo season I will probably repeat the test adding a gas exchange method and see how measured so threshold fit to lactate method. I bought a portable lactate measurement device but had problems with collecting a sample by myself.

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