Interpreting blood lactate test. Also, zone definitions.

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  • #10618

    I have questions on two separate, but related topics.

    Zone definitions

    There have been several discussions on this forum, with (for example) insightful explanations about the detrimental impact about too much Zone 2 training for a highly-trained athlete.[1, 2] I think this is roughly correct:

    • Zone 1 starts at walking / jogging, and the top end of Zone 1 is roughly 10-15 beats per minute (BPM) below the top of Zone 2
    • Top of Zone 2 is the Aerobic Threshold (AeT), defined as the point where blood lactate increases above 2 mmol/L. Or when breathing through just your nose gets to be difficult.
    • Top of Zone 3: this is where definitions differ. Going by TftNA / Uphill Athlete, the top of Zone 3 is the Anaerobic Threshold (AnT), roughly where blood lactate increases above 4 mmol/L (although perhaps better assessed by average heart rate in a 30-minute field test [3]). Joe Friel, Andy Coggan, and others seem to split this Zone 3 into two, defining the top of Zone 4 as the AnT.

    Does it really matter very much, as long as most training is in Zone 1 / Zone 2, with very little sub-lactate-threshold / black hole (Z3 or Z4 depending on who you talk to), and some supra-lactate-threshold intervals?

    Interpreting my blood lactate test

    I performed a blood lactate test yesterday. No lab, just help from my very patient wife! Warmed up for 20 minutes, then took samples at 5-minute intervals with 1 mile-per-hour increases on a treadmill at 1% incline. See table and graphs attached.

    Looking at those numbers, I think my AeT is at roughly 173 BPM, and my AnT is at roughly 188 BPM. The delta between AeT and AnT is about 8%. My takeaway is that I should just focus logging more hours, mostly in the 150-170 BPM heart rate range. Does that sound about right?

    I’ve been fairly consistent this first half of 2018, building up to a couple of 20-mile hikes. But I’m not training for anything in particular at the moment, and volume is low (maybe 5 hours per week on average). I’d like to get faster at shorter distances (half marathon?), although focused on mobility and health primarily. [4] As an aside, Travell and Simons’ trigger point books have been super useful.[5] Six months’ worth of dealing with “sciatica” went away with three minutes of self-massage on just the right spot in my left gluteus minimus.


    [5] There are two volumes, upper and lower body.

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    Anonymous on #10643

    Nice work.

    A few thoughts:

    * I would use more modest increases in speed when you near AeT during your test. For example, it would be good to know what your readings would be at ~168 and ~178. Increases of 0.25 mph may do that.

    * Correct, the definitions of different zone systems are less important than knowing the key inflection points of AeT and AnT. In the simplest terms, you could say that there are just three zones: below AeT, above AnT, and between the two.

    * The closer you can train to AeT (~173 for you), the more aerobic the training effect you’ll get. However, the desire to do so has to be tempered with the fatigue that that training creates. As the gap between AeT and AnT narrows, the metabolic cost of AeT work remains low, but fatigue from that work increases. So an athlete that may have been able to put in hours at AeT in one session when beginning training will need to eventually back off. Future AeT work will be reduced to minutes, and likely done in an interval format, as the athlete becomes fitter. In addition, recovery paces will likely become slower to offset the increased intensity.

    * Training Peaks actually works pretty well for measuring this type of fatigue because it ignores AeT. All TP calculations are done off of AnT, so as AeT increases, TP calculates higher amounts of TSS accordingly.

    I hope that helps.

    Anonymous on #10644

    One more thought: with five hours per week to train and a desire to get faster, I’m sure it’ll be tempting to focus on a lot of high-intensity work. Just make sure that you support your aerobic capacity by keeping 90+% of your training minutes, probably even 95+%, below your AeT.

    Anonymous on #10646


    Congrats on taking the initiative to do this test on yourself and thanks to your patient wife too. You probably nailed the AeT at around 170. With lactate we like to say it is either 2mMol or when lactate has risen 1mMol above its lowest level. So high 160s to 170 s probably a safe bet. Realize too that this changes from day to day based on recovery state.

    Do not use 4mMol as the AnT though. Here’s why. AnT or Lactate Threhsold or Functional Threshold Power (Pace) or what ever you want to call the maximal sustainable pace/HR needs to be determined by a field test. It represents the actual output you can manage to keep up for a long duration. It is by definition = endurance. In your case the inflection point where lactate starts to climb fast is at 183.
    The whole 4mMol confusion comes from the fact that the researchers who originally found this correlation between lactate and intensity tested hundreds of subjects and the average Anaerobic Threshold (their coinage) occurred at 4mMol but ranged from 2.x to 5.x as I recall. Bot for some reason 4mMol has stuck in many people’s minds as defining this intensity.

    It sounds like you running goals so you need to learn to run fast and sustain high outputs for longer times. With your AeT so close to AnT you would be advised to add Z3 and 4 interval training 1x/wk into your plan. AS Scott Semple says you need to keep you base volume high when adding intensity. Start with no more that 5% of your total volume in Z3 each week. When that feels easy, begin to replace the Z3 with Z4 time.

    This is not a training plan, merely a suggestion for a direction to take to build endurance.


    Reed on #10654

    Hi Scott & Scott,

    Thank you for the feedback. Today, I did a halfway successful field test – 15-20 minute warmup, then 25 minute all-out. (No good reason. Heart rate monitor malfunctioned. I didn’t push through for a full 30+ minutes.)


    • Average heart rate ~193-196.
    • Blood lactate 7.0 mmol/L, about 60-90 seconds after stopping.

    My interpretation

    • I didn’t do the test correctly.
    • Assuming my test results are still reasonable, my AnT is closer to 190-195 BPM. So, plenty of room for my AeT to get higher and close the ~13% gap between AeT-AnT.
    • Zone 4, therefore, starts at ~190-195.
    • I’ve got to get off of the computer and get onto the trail, or into the rowing shell, or into the water!

    Sound about right?


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    Reed on #15515

    Following up, six months later – thank you again for your guidance. Feedback is welcomed, but I don’t have specific questions at the moment.

    I’ve worked on taking to heart the refrain of continuity, gradualness, and modulation, with decent success:

    • I’ve consistently kept to a simple schedule of two days per week strength, one long run, and shorter easy runs the remaining four days per week. Weekly volume of only 5-6 hours. Easy / recovery weeks every 3-4 weeks. 95% of running time below aerobic threshold (AeT). (See graph from TrainingPeaks, attached.)
    • AeT heart rate increased to ~177 beats per minute from high 160s / low 170s. Treadmill test with 0.2 MPH increases. Anaerobic threshold (AnT) remains around 193bpm, based on 30-minute field test. (Graph also attached.)
    • Delta between AeT and AnT shrank to ~8.5% from ~11%.
    • Running pace on flat pavement at AnT improved to 7:11 / mile from 7:55 / mile. Not breaking any records, and winter vs. summer may be a factor, but encouraging when the rest of my runs have been at a relaxed 10-minute / mile pace.
    • No injuries. Scott’s Killer Core Routine twice weekly has developed muscles in my torso that I didn’t know I should have. 🙂 And it has improved my range of motion. I wish I had started doing the routine years ago.

    I’ve treated the past 4-6 months as an extended base / transition period. My plan is now to pursue a Max Strength period, following my same schedule listed above. Modest increase in volume, keeping >90% of running time in Zone 1. I’m planning a nine-week block: two hard weeks, one recovery week, repeat 3x.

    Following that, I intend to do a similar nine-week block adding in (not replacing!) one muscular endurance workout per week. I don’t want to invent my own, so I’m looking to the routine provided here:

    Happy holidays, and best wishes for a great 2019!


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    gfilip on #15533

    Hi Reed,

    Great posts and progress, thank you for sharing the details of your training.

    I have a question about your runs during the most recent 6 months where you saw a drastic change in your AeT HR. You mentioned targeting 5 to 6 hours a week with 1 longer runs and and 4 easy runs. What ratio did you use typically for these? Something like a 1.5-hour long run and then 4x 45-minute runs? Did you include very easy recovery runs every week or just when you felt your body needing an easy workout?

    Also, at the 177bpm AeT, are you breathing through your nose without much difficulty? Could you also share which lactate meter you’re using for your tests?



    Reed on #15534

    Hi Greg,

    I more-or-less followed the guidance for early base period training outlined in Training for the New Alpinism: (1) twice-weekly strength / core, (2) one long Zone 1 workout comprising 25-30% of total weekly volume, and (3) the rest Zone 1 or recovery aerobic. [1] The schedule that has worked for me, fitting in with professional and personal obligations, looks like this:

    • Monday & Thursday, 30-45 minute strength
    • Tuesday, Wednesday, Friday, & Sunday, 35-45 minute run (typically on road)
    • Saturday, 90-120 minute run (typically on trail)

    I’m not very fast or very highly trained, so I could probably do more Zone 2 (just shy of Aerobic Threshold) work, but have been happy with my conservative approach. Consistency has been key. A consequence of that low-intensity focus has been that I have not really needed recovery runs or days off. (One exception: a 1h30m fasted run wiped me out for a day or two after.)

    At that 177bpm / AeT, I can steadily breathe through my nose, hold a conversation, speak in long sentences. It begins to get a little challenging to breathe only through my nose.

    Regarding blood lactate meters – Nova Biomedical sells direct to consumer here: For a few other options, see Not cheap, but it was a worthwhile purchase for me. It seems that most medical device manufacturers (e.g., Roche / Accutrend) don’t sell them in the US due to medical device regulatory hurdles and a limited market.


    [1] Training for the New Alpinism, pg. 246

    gfilip on #15539

    Thanks for the details Reed.

    It is pretty amazing to see how high your HR can be while staying in the AeT even though you consider yourself not highly trained. I’m not sure how old you are but with a guess of around 30 (sorry if way off!), the average formulas would put you at around 150bpm for AeT. Unfortunately for me, I very much follow the average and at 32, I’ve been able to bump my AeT up to ~153bpm from ~147bpm or so over the course of a very unstructured year. My numbers are all based on the treadmill HR drift testing but I suspect I am not far off. I’ll be getting a proper lab test done in early January so I’ll be sure to share my results to contribute to what you’ve shared with us.


    Reed on #15542

    My understanding is that heart rate is highly variable from person to person. Formulas and averages work across populations, but the range is quite large.

    I haven’t studied this in depth. A quick search brought me to a 2001 paper that suggested a linear equation for max heart rate of 208 – (age * 0.7).[1] Strong correlation of 0.9, but standard deviation of up to 11 beats per minute. I.e., 95% of 30-year-olds likely have a max heart rate between 165bpm and 209bpm. Not very helpful for an individualized training plan.


    gfilip on #15969

    I completed a lactate and gas exchange flat treadmill test last week. I am attaching my results for reference.

    My baseline lactate seems way high (~3mmol/L) and this makes the lactate results difficult to interpret. I had a day of rest before this test but I suspect I was still carrying some fatigue from the previous week and from a recent sinus infection. Not sure how that affects resting lactate levels.

    During the early stages where HR<140, the levels dropped off to approximately 2mmol/L so I am not sure if I should use the increase above 2mmol/L at around 140bpm as the aerobic threshold, or if I should take an average of the early stage (~2.5mmol/L) and then look at where this baseline increases by 1mmol/L. The former corresponds to AeT of ~135bpm whereas the latter corresponds to AeT of ~150bpm, which better matches what I’d expect based on my nose-breathing and HD drift testing.

    The report indicates an AnT of 174bpm based on the ventilatory threshold whereas my outdoor testing gave me ~172bpm, so quite close. I think it makes sense to continue Z1/Z2 aerobic base building to close in the AeT-AnT gap.

    The metabolic results are more encouraging as the crossover point is right around 140 to 145bpm.


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    Anonymous on #15985

    Good questions.

    The high-then-low lactate presentation is normal. I have that a lot. I assume it may be because of fiber type, but I’m not sure. I think what happens is that it takes a while for the aerobic system to get fully fired up. Once it does, it absorbs some of that excess lactate and you’re left with an aerobic steady state like you have between ~115 and ~135.

    Based on your chart, I would assume that the mid-130s are AeT and work from there. As you do, it should creep upward.

    I could be mistaken, but I don’t think a CHO:FAT crossover point corresponds to AeT. I’ve seen crossovers at AnT, for example. However, I’m not that familiar with them, so I’ll ask Scott J. to chime in on this.

    gfilip on #15989

    Thanks for the notes and input Scott. I agree that I was likely not warmed up enough for the aerobic system to be fully ready and thus the relatively high initial levels.

    As for the CHO:FAT cross-over and AeT, in the “Getting Test Part 2” article, there is this:

    Where the lines cross (the Cross Over Point) corresponds to where fat and carbs each contribute 50% of the total calories. This corresponds very closely to the aerobic threshold.

    but I’d be happy to hear from Scott J. as well.

    Anonymous on #15991

    I can’t be sure about the high lactates. The don’t jive with your very nice Fat/Carb graph. Scott S could be right about lack of warm up. 3mMol resting is very high. The drop from 3 down to 2 is an indication of you aerobic system coming “on line”. the Aer system is slow to respond and take a good warm up to operate at near capacity. The AnT of low 170s look right from this test and corresponds well with your field test. For AeT I’d use 135 range. Thats the highest 2mMol HR and is not far from the 50:50 cross over. There really no down side to doing more aerobic base training and better to do it a bit too easy than a bit too hard.
    Closing the AeT to AnT gap should be your goal for the next few months.


    Reed on #22255

    Following up again, several months later. Here are the highlights from the past six months, with a couple of graphs attached.

    What I did:

    • Average workload of 4h57m per week.
    • Looking at my running and occasional ski, row, etc., but excluding strength training, I’ve spent ~85% of my time in Zone 1 and another ~11% Zone 2.
    • Average mileage of 18 miles per week, longest weeks around 26-27 miles. Probably 60-70% road.
    • Stayed fairly healthy and consistent, averaging one day off every ten days. One exception: caught a bad cold after a vacation last month, took a week or so to recover.
    • I’ve focused on consistency even without increasing the workload much. TrainingPeaks chronic training load (CTL) has fluctuated from around 32 to 38, basically flat.
    • I gave myself freedom to mix up strength training, and not be too rigid. Main focus has been core stability, single-leg / hip stability, and mobility.

    What I didn’t do:

    • I did not get injured. Yay!
    • I did not stick with my plan to add in muscular endurance work. I attempted a couple of these workouts, and they were killer (even scaling back substantially). Couldn’t recover sufficiently.

    What has changed:

    • Heart rate at aerobic threshold (AeT) has increased from ~170 last June, to ~175 last December, to ~180 today.
    • Pace at aerobic threshold has increased from ~9:05 pace last December to ~8:03 pace today

    My plan for the summer is to keep focused on consistent (and perhaps more hours of) Zone 1 work, consistent strength training, and adding in something like one Zone 3-4 workout per week. I had fun and made progress a few summers ago with Tuesday Z5 intervals (30-90 seconds on / off), Thursday Z4 intervals (10-15 minutes on, 5 minutes off).

    Is there anything here that stands out, that I should try to do more of, do less of, or modify?


    PS: Please delete one of these posts, if there are duplicates. I seem to have some issue posting this.

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    Anonymous on #22370

    Reed! You are a UA poster child.

    If you’re getting that response from five hours a week, I think it’s safe to say that you’re a strong responder. I can’t wait to see what happens when you quit your job and put in a few years at 20 hours per week… 🙂

    You’re also a great example of the importance of consistency and gradualness. Great job.

    The only suggestions I have are to:

    * Start recording the speed at each lactate value; and
    * Start testing up to ~4 mM.

    If your AnT is still in the low-190s, then your AeT might end up around ~185. That would be an exceptionally narrow gap between the two. From now on though, the changes in threshold heart rates will be less and less and may even stop. HOWEVER, the good news is that heart rate thresholds are the first to change, but the least important. Your pace at each threshold can improve for years and years.

    As an example, my heart rates at AeT and AnT haven’t really changed in 14 years. They only move up and down by 1-2 beats. Pace, however, has changed a lot. (Although, I’m 45 now, so that is not likely to continue much longer.)

    So if you start recording speeds with each lactate reading, then you’ll be able to build a library of tests to really compare to. That’ll be much more performance-relevant than HR values.

    The second thing would be to extend your lactate tests to include something around ~4 mM. It’s not an ironclad indication of AnT, but I think that it’s a decent proxy. From what I’ve seen in mine and others’ tests, even if actual AnT is at 5-6 mM, the increases in pace (for a 50% increase in lactate from ~4 to ~6, for example) are only single digit changes in percentage speed. Scott J. may disagree, but for me, it’s been a “close enough” value to inform my training without the fatigue that comes from an actual AnT time trial.

    Once you have some reference speeds for AeT and AnT, you’ll find that (with good base training) both will increase and likely converge. And if you’re in your 30s, you likely have at least a decade to improve them.

    Good job!

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