If you want to explore more SS workouts, I recommend joining the “More Sweet spot” team here at TR. They have made a really nice progression where you can work on your sweetspot TiZ up to 2 hours and beyond.
In my n=1 experience, doing 60min TiZ sweetspot set to 90% of FTP is not a big deal from a recovery standpoint. So I would think that it is really good for us that are time crunched. I will say having a well defined FTP, ideally with a long format test is crucial though.
What can you realistically test and conclude in 4 weeks?
Do another metabolic test and see some improvements (or not). And then start a new 4week block?
https://sci-hub.se/10.1152/ajpendo.1987.252.3.E439
This concerns the “lactate producing/consuming fiber” thing. It’s flat wrong that a muscle fiber is one or the other. What wasn’t known (afaik) at the time of this paper’s publishing is that mitochondria also have a dedicated lactate importer. Add this to the fact that trained type IIa fibers are really excellent at oxidatively consuming lactate/pyruvate and that there is no intensity zone & fiber type correlation (I have a 0.31 R^2 between threshold and biopsy confirmed fiber type in individuals of approximately the same weight and vo2max), we can roughly categorize muscle fibers as having two levels of adaptation that aren’t necessarily easy to untangle. First is total potential for oxidative phosphorylation, which is a combination of central and peripheral factors. Second is that we are flexible and adaptable for substrate use within our total aerobic capability. This is not to say ISM isn’t doing interesting and relevant work, he is. His training advice is generally sound. I just disagree with him on a lot of the finer points. I started to raise an eyebrow when I heard him on Attia’s podcast but ignored it for a bit, but when he mentioned iib fibers in humans (which don’t exist) I had to do some digging (and have a little more to do before I invite him on the podcast), and here we are.
To be honest, it really doesn’t matter. Most would be better off just going out and riding more. But overthinking it is fun isn’t it?
I think it’s easy to read and read and over complicate it for what the vast majority of us need, especially when you start talking about people over 50. I get that a lot of the folks here are looking for the optimal plan, but for many who don’t race and just want to be fit and have fun with friends, I think they just want some simple guidelines.
I’m in my mid fifties and think the answer for me is something like one or two days off (with some yoga or strength work if I feel up to it), a Threshold workout or two (with duration of intervals and %FTP increasing over time), and tons of Coggan Z2. Mix in a VO2 every 10-14 days. Take an easy week for recovery every 3 or 4 weeks.
Whenever I try to stretch beyond that, I end up overtrained and realize I should have just stuck to the “simple” plan and it’s consistency.
Absolutely agree with you 100%. Im 57 and think your suggestion of what works for you will also work for me 
Not necessarily related to ISM’s training philosophy but interesting nonetheless - Marit Bjørgen’s training overview:
If you take a look at her yearly training schedule, it’s basically 6 months of basic aerobic developement, 2 months of race specific preparation (ie. build phase) and then competition phase.
The general preparation phase averages about 17-20 hours per week and consists roughly six z2 sessions, four of which are < 3 hours and the remaining two are over 3 hours. Bjørgen did also two mid- or high-intensity sessions (so threshold and VO2max) per week during this period. So basically lot’s of z2 training with some high-intensity sessions can take you all the way to the absolute top of endurance sports.
While you can’t draw conclusions based on one athlete’s training, it think this highlights well that even the best athletes can perform with a relatively simple training regime and fairly sensible overall volume.
Having a career that (on average) I’m on the road 3 days a week (and never the same days) I find I can manage CTL ramp rate much better with zone 2 blocks. If/when I fold in slightly too much intensity during these blocks I find I more easily lose motivation and consistency and therefore ramp rate.
Testing and race results are the data points I can control. Whether zone 2 increases mitochondrial density, lactate shuttling and utilization, lipid utilization, etc…there is no reasonable or actionable way for me to measure those things. I mean I suppose indirectly but, I have no way to verify anything except powerHR and metrics derived from power/HR. So, prior to specification CTL rise is the name of the game for me. LSD just gets results.
Thanks for your input, @freoishome; this is a really productive dialogue.
But, I do think their trial of Polarised training plans need a lot of work. My understanding was they setup the plans with a view to then use the data and online feedback to decide their future plans for periodisation.
Yes, you are absolutely right! As I mentioned above, we are still collecting data on our Polarised Plans. We will use this information to improve and refine them. As you alluded to, Coach Chad always ensures to consider the available data and science when creating and refining all of our Training Plans.
Increasing duration/ time in zone is one important aspect of progressive overload for any Training Plan. With consistency being key to any training program, I think it is important that we listen to your preferences for how to achieve this overload, which will likely vary from person to person. This is why we are making some changes to the ability to customise Workout duration in Plan Builder. Hang tight with us! I note your interest in this feature for Polarised Plans too!
Good point ;-). Make it 8 weeks :-). No seriously…I was planning on buying a lactate meter for DIY @home testing. Maybe before the start of this approach I could do some testing, and after 8 weeks I can do a new test? Maybe also the aerotune metabolic test (I sometimes do this too).
General question. If you want to follow this ‘ISM’ approach, how long before you will see the adaptations. Or even more general…Suppose you do 4 weeks of simply Z2 work (ISM zones), let’s say about 15 hours a week. Would you already see some gains after those 4 weeks? Or you need 8 weeks? But that would be more difficult for me to do 8 weeks of 15hours riding a week.
I was always wondering if I schedulde my work, live around a 15hours training week for a month, what could be done within those 4 weeks for my aerobic condition.
That’s not what I took away at all. I took that it was significantly lower. 78% is well into tempo and I suspect for most people well above LT1. If you can talk comfortably at 83% of FTP you’re a machine and probably don’t need this training anyways!
There is also this video on youtube, which I think is effectively describing exactly the same thing: https://www.youtube.com/watch?v=U17_x1HI6LU&list=WL&index=65
The Seiler low intensity is much lower than ISM Zone 2.
Where are you getting this? He’s talking about sub LT1 levels. He’s also talking about the stress nervous system as the too intense trigger… And using talking as a measure of effort.
This thread has discussed this at length: Iñigo San Millán training model - Training - TrainerRoad
And ISM’s talking test is “intensity where you can still talk, but not comfortably and the other person would certainly know that you are exercising”.
Ok, rewatched and noted this… (missed the “not” earlier 
) but still a bit confused because this seems like tempo if its not comfortable to speak… perhaps high zone 2 (55-75%) or low zone 3.
Is that fair?
If looking at say 1.5 mMol to 2.0 mMol, that’s “tempo” pace for me.
When I’ve centered my training on accumulating a lot of time in this power range, the results have been very positive. I still need a block of threshold and supra threshold to sharpen for competition, but the race legs come around very well and very quickly.
FWIW, I think ISM is describing a very good way to train for athletes who have the time and who value TTE and long term durable riding fitness. If you have 12-15 hours a week, then you’ll develop very durable fitness and a very strong “base” foundation by accumulating a lot of time in the ISM described power range. It’s not that different from what has been known for years.
I don’t think it is limited to higher volume (i.e., 12-15 hours/week). My training this summer was at mostly ISM Zone 2. I rode a max of 5 hours in a week + ran a max of 3 hours in a week + swam a max of 3 hours in a week (average week 9 hours, maxed at 11 hours). I PR’d a sprint distance triathlon (1st in age group), Olympic distance triathlon (3rd in age group) and a 70.3 distance triathlon with only one “hard” session per week. Granted, my training of 9 hours/week is not low volume, but I think the ISM method of training can scale down to lower volumes.
Congrats on the Oly PR - that’s good stuff.
Just for the discussion, not to be argumentative, I don’t think we can compare 9-11 hours a week of structured Triathlon training to cycling directly and specifically not to a time restricted program, cycling only at 4-6 hours a week. Reason is the running is a big stimulus. My experience, have been a competitive runner and cyclist (at same time) but no swimming. The fatigue from running is some multiple of cycling. I also found that running at a high level (for me) helped my cycling performance. But the reverse did not seem to be true as cycling didn’t seem to help or hurt my running. My father had a similar experience. But we obviously shared genetics and environment at the time so not a great control. It’s all anecdote anyway 
Perhaps, I don’t know for sure, but it might be that you were getting plenty of intensity from your running and the zone 2 cycling was great for volume and for specificity of pedaling. If you added cycling intensity on top of running intensity, that could be too much. Don’t know how to factor swimming as I lack experience there. Realize it’s upper body and legs and certainly has a cardiovascular effect too.
So back to pure cycling, and leaving you triathlon nut jobs to fend for yourselves (I kid, I kid), from what I’ve seen with friends and from testing lactate and power type stuff…
(1) The SST programs work pretty well in the 4-6 hour time per week range. The fitness is fragile but the strategy does a pretty good job. With sensible SST programming, fatigue and burnout is controllable. Could be wrong, don’t have data, haven’t seen a good experiment, but I doubt a zone 2 type program is going to be very good if 4-6 hours is all you have.
(2) When you get above say 8 hours, that’s where I think the ISM approach starts to kick in strongly. I don’t know the exact mix of intensity vs zone 2 to perform, or exactly how to progress it, but from what I’ve seen, rigor around adding that ISM zone 2 riding can pay off.
(3) Above 8 hours, and I’ve done that experiment on myself, this Zone 2 / LT1 stuff really works. You get a good base, you get good short and long term numbers with good TTEs. Most importantly, the day to day fatigue is lower than SST plans and when you want to peak, a relatively short block of intensity gives strong results. Because you have the base to go from.
Note - everyone is different and inter-subject variability and response to training is large. But in terms of trends, if you have a decent number of hours (I’ll say 8, it might be more, might be less, no sense arguing about exact numbers as rider to rider variability is a big variable) then erring on the side of having more zone 2 (or base) preparation and then peaking on top of that is probably the better choice compared to over extending on intensity.
An aside - I’m curious how the red light / green light stuff from TR works out. Fastcat and Xert seem to have, or are developing, something very similar. Time will tell, but if those systems work, I bet the benefit will be from adding more red days and not more green days. e.g. nothing new and aligned with build the base and keep your hard days hard and easy days easy.
Congrats again on the PR and for the discussion. I think the running on top of cycling thing could actually be useful to a number of athletes. But cyclists hate running. We don’t even like walking very much (LOL)
Did you only do base riding around LT1 or a mix of ‘normal’ Z2 with the ISM Z2?