All (especially the coaches :))
I have been deep diving into z2 workout benefits especially YT video interviews with Inigo San Milan and Peter Attia. Why? Well after reading about MVP’s Z2 training in the run up to Flkanders and the relative lack of intensity i wondered how that would translate to those of us on 8-12 hrs of week of riding. Inigo is of course associated with training the best riders so his insight is, i suggest, invaluable.
So, to what extent, if any, is his insight around Z2 work, aknowledged by Wahoo coaches ( who may of course be ahead of the insight curve on the benefits of Z2 workouts) and if so to what extent is it factored into the workouts and , especially, training plans? It follows that it must be essential to get that Z2 upper limit just right. How can we be sure without a lactate test?
I know-i watched it all 
I am interested in what the coaches have to say.
This may be variable by individual, but I’ve done a couple of sessions of testing with lactic tests in the recent pasts. The lactic threshold results I got from that were within a few BPM of what SYSTM gives me for Z2 workouts.
133bpm on lactic tests
140bpm on SYSTM tests
I’m sure on one of The Knowledge podcasts @Coach.Neal.H and @Coach.Mac.C discuss this. I just can’t seem to find which one. Pretty sure the gist of getting in the right zone is to make sure you don’t go too hard and can maintain a level where you can still talk in full sentences.
@coaches some input would be welcome 
Thinking back to my long stint as a marathon runner. When I used lots of long low speed training, I felt strong , recovered from training and Races faster, would be moving up the field towards the end of races and be disappointed that there was not further to go so I could make up even more time. Training a lot at “sweet spot” gave me an extra gear. I could race at a higher effort, a higher HR and had better race times than when using z2. Training top end only worked for me if I doubled up on sessions, twice a day was good, I did fade towards the end of races but this gave e the fastest times of all
Alan, I have just been watching a Dylan Johnson YT video where he talks about 2 training sessions a day. It clearly worked for you.
I am a stronger cyclist if I can commute z2, to and from work, 1h a day, and then mix up the training with Sufferfest, sorry, SYSTM, workouts. But when I cannot commute, often for weeks at a time, I find it difficult to get the z2 rides in.
So, I am going to try higher intensity work in the morning some days and z2 later in the day.
Very interesting question. So the way we get aerobic training benefits comes from several factors, oxidation of fatty acids and increasing that capacity via better oxygen delivery. This happens via two training adaptations, increased muscle capillarisation or angiogenesis (MC) and mitochondrial biogenesis or mitochondrial density (MB). The way that MB occurs is via an enzyme called AMPK which responds to high intensity training, and also via calcium signalling which responds primarily to low intensity and long duration training. Low carbohydrate availability also has an impact on MB. MC occurs primarily due to long duration slow intensity (Z2) work which is why athletes on a time limited schedule may hit a plateau where increasing intensity does not yield a greater training benefit or fitness, and more Z2 volume is required to get those benefits.
In terms of how we incorporate Z2 Training, in many of our plans, especially the ones with outdoors rides and targeting longer duration events, we do include rides or 3-5 hours at Z2 to attain the benefits associated with Z2 training. However, just doing 1 hour of Z2 everyday for a week will not yield the benefits of Z2 as carbohydrate availability will not be stressed enough to signal MB and the volume is not high enough to signal MC. So with only an hour available to train, high intensity is better as it will at least signal MB via AMPK. So balancing high intensity during the week, and one or two Z2 rides at the weekend will get the best of both worlds. After all, we’re not all professionals who can do 25+ hours of training a week. And even then, the pros still do a fair bit of super high intensity, but the training benefits associated with that are facilitated by the Z2 work and associated benefits
Thanks for that explanation. It’s one of the best I’ve seen, and really helps explain the structure of the training plans within SYSTM