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I have read elsewhere that below a certain duration, low intensity workouts do not appreciably contribute to base fitness. What is your opinion on this? Are 90-120min rides done at Z2 not actually helping during Base 1/2?

Joe Friel

Ltbarber - As with almost everything in this area, it depends on who we're talking about. But I suspect that for most all athletes 1-2h workouts in z2 are quite beneficial in Base 1-2. When training volume is huge (say 30+hpw) then 1-2h at z2 may not be accomplishing much.



Firstly thanks for the articles on polarisation - they have been very interesting.

Regarding the 80/20 split: 2hrs of above AnT seems like a lot to me! A typical L5 (Coggan) workout would be 5x3 minutes so 15 minutes above AnT. Or the micro intervals you described in one of your other posts might give ~20 minutes > AnT. Even if we look at longer L5 intervals or L4 intervals done at or above FTP (which I think is just above AnT) you're still not clocking up a lot of > AnT time, even if you were doing 3 interval sessions a week.

Is a 90/10 (9hr/1hr) split still going to be effective (or even 95/5 if you only do two L5 interval sessions per week)? Or does the 80/20 split imply you should be doing a lot of interval sessions (even an L5 interval session could be split 65/35 once you include warm up, cool down and rest periods between intervals!)?


Joe Friel

P_Brocklehurst--Good questions. Some of these studies push the subjects very hard to do lots of work above AnT. There is no way that could be sustainable for a season. Even the elite athletes I've known have always been well below 20% >AnT over the course of a season. And usually <10%.


Very interesting information as always

I'm trying to rebuild my tri base after a year of no racing and reduced training. Looking to get back to Olympic and HIM. (8 years of prior racing). I now have 3-4 hours per week to bike and 3-4 to run. In this base rebuilding if I spend 10-20% above LT should the remainder be zone 1 or 2. And none in 3-4?


Joe Friel

marc - Yes, something like that, altho 20% sounds awfully high for z5, especially in base period. I'd suggest more like 5-10% at most. But then there are a few variables here that I don't know about you. So I'm just guessing.


Thanks Joe. 5-10% above LT sounds more realistic.

I realize that my original question may have been worded ambiguously. What I meant to ask was whether the remainder should be only in zone 1 or is zone 2 ok too.

Thanks again.

Joe Friel

marc - In polarized training the lowest zones is typically everything below aerobic threshold. Using heart rate and my zones system that's about the bottom of zone 2 (roughly 30bpm


If true this has leads to a number of conclusions:
- TSS is pretty meaningless
- Sweetspot is the worst zone to train in
- The first rule of training is not specificity (unless you are training for ultra endurance events)

I will need a lot more convincing about this. Not just from theory but personal experience. Last year I tried out doing more low effort zone work. It was boring to do and led to a flat season.

I am now back to my old training which has a basic rule of thumb. If you are not having to breathe using your mouth you are not training. So I do what I consider to be zone 2 but this consists of a solit 3 hour session at 250W/85% LTHR The difference in terms of performance is marked. I ride better and feel better

Larry Tieman

What is your opinion on how this would affect triathlon training. Specifically, does it apply to each activity alone or to the training day?. To clarify, do you think it is better to do a hard day of running and cycling or alternate a hard day of running and an easy day of cycling with easy and hard being defined as in this article? In your opinion, does it have any bearing on swimming and if so, how to measure (with only rudimentary tools).

Joe Friel

Larry Tieman--There are no precise answers for your questions. Too many variables. But in general I would take it to mean that you must balance the stress of hard training with very easy days. The greater the stress, the easier the easy workouts. Fatigue is cumulative regardless of which sport it was created by. So a hard run needs to be balanced by an easy workout whether this is a swim, bike or run. The best gauges of intensity don't have to be high technology. Perceived exertion works quite well and always has.


Hi Joe,

As I'm sure you are aware, it's difficult for the majority of triathletes to get below 2 mmol lactate during aerobic swims. I typically have less developed athletes use a pool buoy on longer swims to keep them slightly below aerobic threshold. I know that a lot of swim coaches would frown upon this. What's your take on it?

Joe Friel

DynaMultisport - I don't see any problem with that. There are times when using pull buoys is fine.


Hi Joel.

Thanks for great books and blog. I've decided to go back to building my aerobic base by using heart rate training for as long as I'll se an improvement, but I find the amount of information on how to accomplish this best a bit confusing.

You write elsewhere that the aerobic threshold is something to the like of LT - 30. My LT is 178, så my AeT should be around 148. Phil Maffetone's formula would put me at 148 too, me being 32. My zone 2 is 152-161 using your run formula.

Now, some coaches says 'train below AeT', others say 'train at it', while you seem to advocate training above it in zone 2 (in total heart rate training you state that you think it's the upper half of zone 2 that's most beneficial for aerobic development).

Some coaches says it harmful to train above the threshold. Do you disagree?

My linke of thinking would be, that it's more about training volume and recovery - so that if I can spend a huge amount of time, say more than 15 hours per week, below AeT would be best, whereas on a limited training time budget (let's say 4-6 hours per week, which is my available time at the moment), zone 2 is better - maybe even zone 3 if time is even more limited?

Hope you can clear up some of this confusion.

Joe Friel

jeppe--Short of having a gas analysis test done in a lab we're just guessing at AeT. So do what feels like a 3 on a 0-10 scale.

Scott Sutherland-Thomson

Hi Joe, after reading a few good articles on 80/20 training I've been convinced to try it. I'm doing about 20% (2.8hours) above FTP and the rest (11.2hours) at a maximum of top of Z1 HR. I've been training at an elite level for a couple of years but I'm actually finding this quite tough, although doable. The hardest thing for me to accept is that my TSS has considerably reduced, I'd say by about 25%. Should I be concerned by this reduction? I train for ultra-endurance mtb races.

Joe Friel

Scott Sutherland-Thomson--I understand. It's always scary when training metrics drop. But that doesn't necessarily mean anything bad. For example, Gwen Jorgensen (a triathlete) went to 80-20 last year. Her average run pace dropped to 8:30/mile because of this. Pretty slow for her. But she won the gold medal in the 2016 Rio Olympics.There's only one way to find out, I'm afraid. Good luck!

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