Ironman Training – 200 Hours In The Wrong Zones? Not a good idea.

ironman-logo-iconA lot of the Ironman plans I looked at rely on Training Zones. Either POWER zones or HEART RATE training zones.

Much of the training is in Zone 1/2. Broadly speaking the Zone 2 to Zone 3 boundary (AeT/LT1) represents going from aerobic to anaerobic. With caveats, this specific boundary is a ‘real thing’ that represents physiological changes in your body and not just an arbitrary number.

Source: Training Peaks. Illustrative, relative amount of time spent in Z2

LT1 is typically recognized as the workload (watts) corresponding to a sustained increase in blood lactate concentration above resting levels (typically below 2.0 mmol/L) during a progressive exercise test.

LT1 is often called the lactate threshold by sports physiologists HOWEVER most of us call the Lactate Turnpoint (LTP, AnT) the Lactate Threshold. so be wary of that when you read around this topic.

So it seems to me that if you, or I, are about to enter into 200 hours of training time then it might be a really good idea to get the training zones as ‘correct’ as possible?

Whether you finish an Ironman in 9, 10, 12 or 16 hours, you will perform better as your body becomes better able to use FAT as a fuel source. Training in zone 2, and less so in zone 3, goes a long way to achieve that. Zone 2 training uses fat and carbs as a fuel source and recruits Type I muscle fibres (slow twitch). Zone 1 training is pretty much entirely fuelled by fat. Zone 4 training, and above, uses pretty much no fat as a fuel source.

Is your Zone 2 correctly estimated?

If you have a power meter you will most probably know how to do an FTP test. From that result, you will back-calculate your likely Zone.

If you don’t have a power meter then you will be likely to be looking to train by Heart Rate and maybe Perceived Effort.

For the longer, slower stuff I actually quite like working to perceived effort – but overlaying that with cursory consideration of the ‘same’ zones for power and HR, just to ‘keep me honest’. I prefer to know when HR or power thinks I am in Zone 3 and then react accordingly IF I want to. Most usefully I do this on hills where I am VERY inclined to push it too much. Pushing it too much works for a while but NOT for 9, 10, 12 or 16 hours.

I DO like and follow zone based training however I am not entirely convinced of the accuracy of my Zones over longer durations. Taking an arbitrary measure of what I can do for an hour and then extrapolating a fraction of that to >>9 hours seems to me like something to approach with care.

For example, I teeter around +/- 4w/kg on the bike, which I guess is OK. However, I’ve found that extrapolating my resulting power zones to durations over 2 hours doesn’t seem to work. My real CP120 seems to be quite a bit lower than what I should be able to achieve…same for my CP180, etc.. Probably the main reason for that, as a ‘time-crunched athlete’, is that I spend PROPORTIONATELY more time training below 60 minutes than I should. So I can perform a CP30 test pretty well but not a CP120.

My understanding is that my/your CP curve will have several inflexion points, which vary for individual even with a fixed FTP, this is because our bodies’ energy sources and endurance capabilities vary. You could do 3- or 4- hour rides most days and I could do nothing over an hour most days, yet our FTP (assuming identical weight) could be the same based on a 20-minute test protocol. Yet you could be notably faster over longer distances over multiple hours. Perhaps your pedalling technique is better (less energy required) or you are more aero (less energy required) or just simply that you exhibit a higher aerobic coupling than me because of your training regime. So your inflexion point at over 3 hours would be higher than mine. ‘Obviously’ you will perform better over the 5/6 hours of an Ironman bike.

I use the ‘Extended CP’ model in Golden Cheetah to determine my mFTP (modelled FTP) and, indeed, the entire CP curve – shown partly below for the last 3 months. This tells me that I have done 3.5-hour rides in Zone 3. I could probably do that level for longer but that’s what I’ve actually done. It then has a token ‘tiny’ amount of ‘proper’ extended performance in my Zone 2, shown below. In one sense this is good in that I can theoretically get good Zone 2 outputs at 5/6 hours BUT quite worrying in that I’ve never got anywhere near achieving that in the recent past.

So whilst I always have done lots of Zone 2 training, it’s fairly clear that I need to do it for significantly extended periods as I’ve hardly ever done that and will definitely need to do that for my Ironman. If I don’t do that then I may need to do the bike in Zone 1…which I would have thought would be considerably slower 🙂

Maybe my zones are right but my ‘time-in-zone’ is not?

Fairly obvious, I suppose.

My Ironman Secret: I have done lab tests for cycling and running to determine my LTHR/AnT/OBLA and they produced values that were NOTICABLY different to those from the Friel method. The Friel method produced higher results. I also used BSX Insight and that, surprisingly for me, pretty much agreed with the lab test.

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5 thoughts on “Ironman Training – 200 Hours In The Wrong Zones? Not a good idea.

  1. Great article – very interesting. We all know the Z2 theory but getting the application right is the tricky part (once you are over the hump of doing Z2 at all..). I take it that your observation is that the lab data/Insight data is reliable and the Friel based self tests less so? If yes that seems to be making a case for the Insight.

    1. in my case of ‘me’ my opinion is that LT2 from a lab test is more accurate than what I have got from a friel test
      although I use modelled zones (Tom Lawton, previous commenter also uses same golden cheetah ones I believe) my argument ‘against me’ is that I have done sufficient levels of training at longer durations therefore the models do not have sufficient data to give the result I’m looking for.

  2. Thanks for the post. Wondering whether measuring O2 and CO2 in a lab test to calculate the respiratory ratio might not be a more direct and more “reliable” way of determining what fuel you are burning – and thereby more likely to get the zones “correct” than using lactate? Any thoughts or experience with that? The other thought I had was whether it is “correct” to assume that the zones would stay constant over the 5/6 hours spent on the bike – nowadays it would seem fairly “natural” to assume that nutrition (or the lack of it) might shift the zones, how about fatigue?

    1. caffeine/beet-it DEFINALTELY raise HR
      so if you only have them on race day your race day zones are different to your training zones…kinda silly if you think about it
      what I was getting at with the article was really ‘aerobic coupling’. coming from that angle
      some of the XERT tools look produce fat/carb burn estimates as, I think from memory, does gomore.

  3. Great overall description. Do checkout Xert’s “Lower Threshold Power” as a metric that is also measure Xert picks up from your power data. We identify it as a key intensity turnpoint when “endurance energy” stores (as they are going to be referred as) are consumed to a greater degree. The reduction in endurance energy itself affects your FTP in our modeling, for example.

    Many of our new SMART Workouts have LTP and percentages of LTP as part of their workout definition (new feature). We also use fatigue during workouts to impart additional strain during lower intensity intervals. Our “SMART – Iron Man” workout is one such workout.


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