Bike Z2

Viewing 5 posts - 1 through 5 (of 5 total)
  • Author
  • #9784


    I’m doing an Ironman Plan, and have a question about zone 2 power on the bike. Also, I’m only doing the Bike/Run portion, and substituting some easy bikes/runs and upper body/core work for those swims.

    I have been using the plan since first part of October, and have repeated the first 4-6wks until I was 22wks out from my event, which is where I’m at now.

    I use a trainer in erg mode, along with Trainer Road. This put the power target in the middle of the suggested range…211 watts, with is 76% of my FTP.

    Why does 80/20 zone 2 bike power go all the way to 83% of FTP? Seems like most everyone else caps zone 2 at 75% FTP.

    My real concern and following question are; I seem to feel fatigue building high enough that my other workouts and recovery seem to be suffering, or are on the verge of suffering.

    Can I drop all my zone 2 bike power targets closer to 70%? I did this the last couple of weeks and my easier rides and Z2 portion of the interval/threshold felt better. I don’t want any training adaptations to be limited, but I also don’t need to bury myself now that I’m actually starting the full 22wk schedule.

    Thank you,

    David Warden

    Andy, the short answer is: for sure, you have complete flexibility to adjust your intensity within Zone 2, including lower Zone 2. A few points I hope will answer your question:

    – The division between easy and moderate intensity in the 80/20 system is empirical. It’s VT. However, the division between Zone 1 and 2 is purely practical. “Easy” really extends from the bottom of Zone 1 to the top of Zone 2. When we say Zone 2, you can actually use Zone 1 on days when you need it. Feeling strong? That Zone 1 ride can include some Zone 2. We created Zone 1 to give athlete permission (and in some cases, force them) to slow down more than they were used to.

    – I don’t recommend ERG mode. It forces you into an intensity that may not be best. I understand you can dial it back from the default 50%, but once you get into a cadence it’s hard to break out of that set intensity. Mentally, athletes have a hard time going below 50%. The beauty of zone ranges is that you can adjust each day based on objectives or feel, and ERG mode takes away much of that flexibility and advantage. ERG mode could be the primary cause of your fatigue. Plus, you can’t use ERG mode in a race, you eventually have to learn how to pace independently.

    – Of the 80% easy, our plan prescribe 50% Zone 1 and 50% Zone 2, so you’ll get a ton of really easy options (but again, if you are always 50% penetrated in Zone 1 you can’t fully take advantage of the easy recovery).

    – Regarding the 75% of FTP as the upper end of Zone 2 from other methods, let’s compare 80/20 to Coggan. Coggan lower Zone 3 includes the upper level of 80/20 Zone 2, and Coggan Zone 3 is mostly 80/20 Zone X, which we don’t use. We also prescribe far more time in Zone 1 than Coggan.

    Let’s assume two athletes each spending 5 hours a week cycling, one using 80/20 and one using Coggan. Let’s also assume that each athlete hits the middle segment of each zone for every workout in ERG mode. The 80/20 athlete would look like this:

    80/20 Athlete
    80% easy Zone 1 and 2 = 4 hours
    50% Zone 2 = 2 hours at 76% (middle of 80/20 Zone 2)
    50% Zone 1 = 2 hours at 60%

    Total easy average FTP penetration = 68% for 4 hours

    Coggan Athlete
    60% easy Zone 1 and 2 = 3 hours
    75% Zone 2 = 2.25 hours at 65% (middle of Coggan Zone 2)
    25% Zone 1 = 0.75 hours at 50%

    Total easy average FTP penetration = 60% for 3 hours

    In summary, the % of FTP done easy between the two is not that far off, but the total time spent easy is far more with 80/20. You’re 8% higher penetration into FTP with 80/20 but spending 25 more time easy. 80/20 can afford a higher Zone 2 because we prescribe so much more time in Zone 1 and avoid Zone X (second half of Coggan Zone 3) all together. Also, I thinking I’m being generous when I say 60% easy with other training systems, the default is 50% easy for most athletes.



    Thank you David, I really appreciate the time and explanation!

    The time in zones makes sense.

    I understand the concern with ERG mode. I feel like I have a pretty good ability to pace with my power meter and RPE, though I’m sure I could do better. I’ve been training with power for 7-8 years, and I think that helps. That said, I like to watch TV while riding and ERG mode helps me pass the time more easily. I think I’ll at least do a ride or two a week out of ERG mode.

    Now that I have a better understanding on the Z2 range and how it fits in 80/20, I will have no problem being comfortable adjusting efforts in that range.

    If anything I’m like most people you probably deal with and have more of a problem with dialing back vs more is better. I might even drop it lower on the rides that I’m doing in lieu the swimming.

    Do you have experience with Garmin running power compared to Stryd? I purchased an early version of the Stryd, and had some issues and ended up returning it. Then Garmin released running power calculated through the HRM or a waistband pod. I already had the HRM and Fenix watch, so enabled the power and have been collecting data for a few years…I’ve never run with power or trained with it.

    Thank you again, and appreciate such a quick response.

    David Warden

    In general, the Garmin solution is going to work better than the Stryd solution at this time. Garmin is not terribly motivated to make it easy for Stryd to succeed on their hardware, as a direct competitor. I like the Stryd device more for sure, but it may not play well (now or in the future) with Garmin.

    However, the Stryd works amazing with an Apple Watch. Stryd has much more customization on the Apple platform and has done a great job. It works really well with the 80/20 workouts.



    I do have an Apple Watch and none of my running events would exceed the battery life. Though, I will probably get back into Triathlon and move up to an Ironman distance and I doubt that my Apple Watch battery would last that long.

    I wish Garmin would at least do more with the running power. Currently you have to look at it on an individual workout level. I might give running power another shot.

    Thanks again for all you do!

Viewing 5 posts - 1 through 5 (of 5 total)
  • You must be logged in to reply to this topic.
Posted in


You must be logged in to create new topics and to reply to topics.