Confused about training status / load.

"The algorithms are all based on averages so will/can never be truly personal. Use them for guidance not prescription."

As I see it, there are a few Levels of training:
A - Beginners who should just get on the bike as often as they can.
B - Intermediates who can start playing around with heart rate monitors and generalized training plans.
C - Advanced who have been doing this long enough to figure out and adjust their own training plans.
D - Elite (or very serious amateurs) who can afford to pay someone to work out training plans for them. This will generally mean signing up with Training Peaks and from there the coach will see what's up figure things out on your behalf.

I see myself at Level C. 
I'm not paying someone else (with a Training Peaks subscription on top of that) every single month. I rather spent a once of amount on a high end Garmin device with built in Firstbeat algorithms.
I get that it is not a "prescription", but I choose to believe that it is more than advanced enough to take the "real world" info my Garmin provides and from there give personalised "guidance" that will help me to make informed decisions regarding my training.

"Note also the chronic training load is a rolling number where high loads will have a diminishing effect as time progresses. The lefthand edge of the training load suggests an elevated training load that was decreasing in subsequent weeks."

Thanks for this.
So I'll just check the recommendations when planning my ride(s).
Ater syncing a ride I shouldn't expect the numbers to "add up" so to speak. The algorithm will throw some stuff out, keep some others and adjust it's recommendations accordingly 
I'll not break my head about it.  ;) 

No. My zone 1 goes up to 75%, which is half way through your zone 3, .... you probably noticed that you can set them as you like which is the meaning of "arbitrary". So instead of talking about zone 1 better talk about x-y% HRmax. My zone system is based on the Norwegian Olympic Federation. It makes more sense from a physiological perspective.

Ah, I see. You use a different method of calculating your zones.
For now I'll stick with the basic one as described by Garmin:


Think I figured out how / where to spend my time to get the results I'm looking for:
* To fill up the Low Aerobic bar, I'll stick to Zones 1, 2 and 3.
Where time in Zone 3 will presumably fill it up quicker than time spent in Zone 1 and 2.
* To fill up the High Aerobic bar, I'll spend time in Zone 4 (maybe even Zone 5).
* Filling up the Anaerobic bar is not a matter of spending time in any zone. It is a matter of doing some high intensity intervals / "spikes".

Zones are not arbitrary, though there exist different approaches as how to define them. The typical definition for a 5 zone model is:

Z1+Z2: Below Aerobic Threshold (Talking+Nose breathing possible)

Z3: From Aerobic Threshold to Anaerobic Threshold (Anaerobic Threshold is often measured/known by athletes, it is basically around your 45min max effort average pulse, say your 10km average pulse)

Z4+5: Above Anaerobic Threshold

You can use HRmax percentages as starters, but really you should *measure* the Aerobic and Anaerobic Thresholds, by doing a nose-breathing test and a 45-60min all-out effort. The points these thresholds are at are very different between individuals, so guessing via a HRmax% can be very wrong.

Once you have the Zones, Low Aerobic is Z1+Z2, High Aerobic is Z3, Anaerobic is Z4+Z5.

Have a look here: https://www.researchgate.net/profile/Stephen_Seiler/publication/46403553_What_is_Best_Practice_for_Training_Intensity_and_Duration_Distribution_in_Endurance_Athletes/links/0fcfd50ab8a2290995000000/What-is-Best-Practice-for-Training-Intensity-and-Duration-Distribution-in-Endurance-Athletes.pdf

There they explain different zone models and how they apply. Note the 3 Zone model that is split by just the two thresholds, this is what I am talking about, and I believe this is what determines low aerobic, high aerobic and anaerobic first beat numbers.

Even Seiler states: "...is divided into five somewhat arbitrary intensity zones". And note that zone 1 is going to 72%, in other publications from him to 75% which is very different from the standard Garmin and Polar scale. The point is: it is pointless of talking about "zone 1" without defining it.

Yes, doing 5 zones is somewhat arbitrary, since you only have two dividers (Aerobic Threshold [or VT1] and Anaerobic Threshold [or VT2]), hence in the paper I mentioned Seiler mostly talks about the 3 zone model, which, coincidentially, is exactly what Firstbeat also do, with their low aerobic, high aerobic and anaerobic bins. So while I agree that *some* of the dividers of zones are fuzzy, others are quite hard and measurable, Aerobic Threshold and Anaerobic Threshold are measurable values that *should* divide your zones, as training effects are quite different depending on which side of the thresholds you are.

Point is: Know your two thresholds. Divide your zones as you please, but keep in mind if you are in the green zone (can talk), yellow zone (lactate is steady but talking is harder) or red zone (lactate is not stabilizing anymore). Doing random assignments as per maxhr% is going to net you a poor picture of your training, especially if your thresholds are not close to where the average runner has them (since these maxhr% models are based on runner population averages).

As I said in this thread https://forums.garmin.com/sports-fitness/running-multisport/f/forerunner-945/204662/training-load-focus-is-based-on-what-heart-rate-zones-are-so-different

Guessing VT1 from maxHR (or from Anaerobic Threshold) can be very far off individually, e.g. in the book "Training for the uphill athlete" p63 there are three athletes compared, one has his AeT@56% maxHR, the second at 73% of maxHR and the third at 88% of max HR.

Obviously it makes quite some difference if your "Green Zone" ends at 56%, 73% or 88% maxHR, but for those three athletes, thats where it ends.