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

A 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.