Terry:

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
Scott

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

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

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

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?

-Reed

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 https://www.trainingpeaks.com/blog/joe-friel-s-quick-guide-to-setting-zones/, 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.)

-Reed

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.

Scott

pshyvers1
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

Scott