Confusion – Zone 1 + 2: TftNA vs TrainingPeaks

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  • #9452

    Hey everyone,
    Onto my 2nd season of using TftNA and have really enjoyed and benefited from season 1 (90 day NOLS expedition, fit and injury free, yay!). Much thanks to Scott and Steve for a great program 🙂

    Newbie question:
    TftNA says Zone 2 is “No Man’s land” but Training Peaks says it’s the most important zone. I’m just entering the rabbit hole of TP and am having a hard time reconciling the different zones, names, etc, between TftNA and TP.

    What should I go by for this season’s training? Should I do the Max HR test then apply TftNA zone % calculation? Use one of TP’s “auto calculation” methods (Joe Friel, Peter Keen, etc, etc)?

    Thank you!

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    Anonymous on #9474


    I don’t how to make this post a sticky but I have answered this several times before. Its a good question so here comes the loooonnng answer:

    For well trained endurance athletes, which was what my background as an athlete and coach has been, Z2 IS a dangerous zone to spend too much time in. The reason is this: A well trained endurance athlete will have an aerobic threshold very close to his/her anaerobic or lactate threshold. Often these two important metabolic points will be separated by as little as 6-7% in HR. That is going to be around 10 beats. That gives a very narrow Z3 (Aerobic threshold, recall is at the top of Z2 not as the misprint in the book saying Z1). So when the fit athlete is training near AeT he/she is also training near AnT. AeT running pace will often be within 5% of AnT running pace. For these fit athletes, that’s FAST. Too fast to train a high volume. Even though the metabolic stress is the same for any athlete (fit or not) in this aerobic zone, these speeds impose a very high neuromuscular load that needs more time for recovery. Doing a high volume of Z2 for these folks will lead to overtraining. They need to do most of the aerobic base work in Z1 and then do more high intensity work at Z3 and Z4.

    However, when a person with aerobic deficiency (ADS) runs at AeT (top of Z2) the pace will be quite slow. Often these folks are dismayed how slow they must run to stay in their aerobic zone. For them the neuromuscular loads are quite low at these slow speeds. So, those with ADS can handle all or nearly all of their aerobic base building work right up at their AeT. For them Z2 is NOT a black hole.

    How did this make it into the book? With my rather skewed, high level athlete and coaching experience I was not fully conversant in ADS as it presents in recreational and none endurance athletes. I have learned a lot since that time and now see that in order for those with ADS to see their maximum gains they need to train right near AeT.

    I hope this helps

    Anonymous on #9482

    On a related tangent, Training Peaks’ metrics work quite well for tracking training stress, because they (coincidentally) ignore the phenomenon that Scott J. describes.

    Training Peaks uses the anaerobic threshold as the main reference point so the software does a pretty good job of tracking fatigue. (However, for the same reason, I don’t think it does a good job of tracking fitness.)

    So if you train according to your aerobic threshold (as Scott J. describes) and use Training Peaks to track fatigue, you’ll naturally see greater fatigue building in Training Peaks as your aerobic threshold approaches your anaerobic.

    I hope that makes sense.

    madanyang on #9487

    So are you saying that the CTL in Trainingpeaks is not reflecting the fitness at a given point?

    Anonymous on #9489


    CTL, just like TSS and the other metrics that the TP model displays are proxies for an incredibly complex series of physiological responses. With the way most of us use TP, the TSS is based off one metric which is HR. TSS forms the basis for the mathematical model that spits out CTL, ATL and TSB. hrTSS is the least accurate way of measuring training stress of the others TP offers: Power TSS using a power meter on a bike being the most accurate and Pace TSS using running pace on the flats being next most accurate. Those 2 options won’t work for us so we have to use hrTSS. HR is not the best indicator of training load because HR is not a perfect reflection of the stress your body while training. In the aerobic zone (under the anaerobic threshold) the relationship between HR and pace is linear so its a decent measure of stress. A 10% increase in pace will result in the same increase in HR anywhere along the HR/pace graph. In the anaerobic zones it is nonlinear. Above AnT each increase in pace will yield a smaller and smaller HR increase till you reach maxHR. Likewise when you impose high strength loads in the training such as ME work, the HR/TSS ratio goes out the window.

    If we magically had a hiking power meter that could account for gradient, footing, altitude, weight on your back, like a bike power meter then we too could have a very accurate TSS.

    All this means is that the less perfect your TSS input into the TP model is, the less accurate is the CTL output. CTL is a crude measure of fitness just as ATL is a crude measure of fatigue. But they are the best we have ever found. Do not blindly adhere to the numbers. Learn from what they tell you. Compare the TSS the model spits out to how you feel, how fast you recover etc and adjust accordingly and you can refine the model for your individual use.


    madanyang on #9502

    Thanks Scott for the detailed explanation. This is my second year with the TFNA plans and Trainingpeaks and I have learned quite a lot less year, and I am going on the cautionary side this year. I am not making any TSS adjustments to ME workouts or hill climbs (based on elevation and carried weight) but rather the following day how does going up the stairs feel like and then if necessary either move workouts if possible or do a very easy recovery workout. So far this seems to work yet the real answer will be defined when I am on my climbs in the following months.

    Nevertheless it is a learning process and I am sure next year I will be adjusting other things as well.

    Thanks again

    Thrusthamster on #9510

    I just realized what I thought was 75% of my max HR going by age is way less than I thought it was (142 BPM) and my AeT is around 155.

    I’m wondering Scott, at what point should someone who’s “new” (been training endurance for 1.5 years but still consider myself pretty bad at it) transition from training near AeT as you say, to staying at 55% to 75% of max HR like you prescribe in the book, if those two values are different?

    Anonymous on #9511

    Don’t go by age. Once you know your own thresholds, generic formulas are no longer useful.

    TerryLui on #9529

    Thanks a bunch for all the info everyone! Lots to digest and consider.

    Scott J: apologies for asking a repetitive question, I tried to do a search for it but the search function on the forum kept asking for a password and ultimately didn’t work.

    Reed on #9533

    Scott J.,

    I’m a visual learner, and have several lactate tests’ worth of data to draw on. Maybe this can help others, too. In the attached graph:
    – Top end of Z4 / Sub-Lactate Threshold is where blood lactate concentration hit 4mmol/L – AnT
    – Bottom of Z4 / top of Z3 is simple average of AnT and AeT
    – Top end of Z2 / Aerobic is where blood lactate concentration crossed 2mmol/L (or best guess, in the left-hand bar) – AeT
    – Bounds of Z1 are estimates, and of course that’s really a gradient not a sharp line

    My interpretation based on your explanation:
    – Aerobically deficient, or at least poorly trained, towards the beginning of my first structured training cycle a few years ago. I could train all I wanted in Z2 / Aerobic, and even a decent amount in Z3; the training stimulus was purely aerobic.
    – Moderately trained, a few weeks before my first 50k (end of that training cycle). I had substantially improved my top-end lactate threshold as well as dramatically tightened the gap between AeT and AnT, down to ~9% of AnT. Training distribution was bimodal, mainly Z4 15-minute intervals / Z5 3-minute intervals and long-duration Z1-Z2.
    – Highly trained (for me!), a few weeks before a road marathon. Numbers similar to a few months prior. ~5% gap between AeT and AnT.

    For that road marathon, I was self-coached, using Pfitzinger’s marathon prep plan without sufficient base training and using Joe Friel’s heart rate zones. It looks as though I did a substantial amount of running at the top end of Z2 and even into Z3. It sounds as though the challenges I encountered were perhaps largely caused by overtaxing my neurological system and muscular endurance capacity.

    Am I correctly understanding what you wrote in your initial response?


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    Anonymous on #9536

    I’ll let Scott J. comment on the specifics, but a few general points first:

    • Great job on closing the gap between AeT and AnT;
    • Typically, lactate curves are diagrammed like this with La on the vertical axis and intensity (via HR, power, pace, etc) on the horizontal axis. Without the lactate values on your chart, I find it hard to compare them;
    • I could be mistaken, but I believe that AnT (~4 mM) is typically used to estimate the bottom of Zone 4 rather than the top; and
    • Zone 1 has a greater impact than just recovery, especially when AeT and AnT are close together. For well-trained athletes where AeT is close to AnT, Zone 2 training becomes very stressful. So the bulk of their training will be in “Zone 1”. As such, I would label training below Zone 1 as recovery.
    Reed on #9537

    Hi Scott S.,

    Is there a way you’d suggest thinking about the bottom of Zone 2 and the bottom of Zone 1? What I’m reading in this thread is that not only does Zone 3 shrink / disappear, but a large range of aerobic work—conversational pace, lactate <2mmol/L—is too strenuous for high volumes.

    In much of the reading I’ve done, people like Joe Friel have used Zone 4 as “sub-lactate threshold” (see, TrainingPeaks built-in zone calculations, etc.).

    More traditional lactate test data points in the attached picture, using an exponential fit rather than just connecting the dots. The three tests align to the first graph I posted – specifically the 2mmol/L (top of Z2) and 4mmol/L (top of Z4) data points. (The first test had some issues, but whatever way you slice it I wasn’t in shape.)


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    Anonymous on #9539

    That’s definitely a huge improvement, especially in between the first two tests, only three months apart. Good job.

    I could definitely be wrong about L4 as the bottom of Z4.

    For both that and a definition of Z1, I’m afraid I can’t offer much. I don’t use the traditional five-zone system. (I use AeT as my benchmark intensity and then percentages of that intensity for different workouts. At and below AeT, HR is close enough. Above AeT, I use pace.)

    However, I think that the zone system was originally designed as breakpoints between whole-number changes in lactate (1,2,3,4,4+). If you want to think in terms of a five-zone system, I would define Z1 as <=170 and Z2 between 170 and 180.

    Anonymous on #9641

    Hey Reed,

    I touched base with Scott J. on the typical breakpoints for zones 3 and 4. Here’s his response:

    Statistically, 4mMol may be a good indicator of the top of Z3, bottom of Z4. But a much better way to determine this point is to do a time trial at max effort for 30-60 min (30 for less fit, 60 for fit due to local muscular fatigue impacting the sustained effort) Find avg HR and bingo you have the top of Z3. Lactate would NOT be a good way to determine this. A field test is much better and better than a lab. Do the test in a sport-specific way.

    I hope that helps.


    pshyvers1 on #10826

    Kind of a tangent, but you say:

    Aerobic threshold, recall is at the top of Z2 not as the misprint in the book saying Z1

    I’d not heard of this misprint. Is there a list of misprints/erratas found in the book anywhere?

    Anonymous on #13398

    No there are not a lot of misprints in TftNA. This one and the failure to more clear about progressing only aerobic volume (hours) when laying out a training plan. Both have been corrected the latest reprint which is due out soon.

    The Z1 or Z2 AeT issue is only a matter of convention and does not in any way change the principles behind or the way in which you train or manage training loads


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