Plan Builder's short VO2 Max Intervals

Plan builder keeps giving me VO2 Max workouts with very short intervals (example of Merced -2 copied below). I’m doing all my rides outside and short intervals like the ones that it keeps serving up are very annoying to try to do outside. I’ve been replacing them with workouts of similar progression levels that have longer intervals (for example Coco). I guess I have two questions:

  1. Am I missing something in not doing these short intervals?
  2. How in the heck can anybody execute a 20-40 second “on” interval outside? I can easily go hard for 20-40 seconds but hitting a specific power target for only 20-40 seconds outside just seems unworkable to me.

Merced -2

Outside• VO2 Max 5.2






Scheduled for Wahoo


Power Based|RPE Based

Warm Up:

  • Ride for 7 minutes 30 seconds gradually raising your power from 132 watts to 211 watts.
  • 20 seconds at 317 watts, with 20 seconds recovery.
  • 25 seconds at 330 watts, with 25 seconds recovery.
  • 30 seconds at 343 watts, with 30 seconds recovery.
  • 40 seconds at 356 watts, with 2 minutes recovery.

Main Set:
5 sets of the following, with 5 minutes rest between sets:

  • 40 seconds at 356 watts, with 20 seconds recovery.
  • 40 seconds at 343 watts, with 20 seconds recovery.
  • 40 seconds at 330 watts, with 20 seconds recovery.
  • 40 seconds at 317 watts, with 20 seconds recovery.
  • 40 seconds at 304 watts, with 20 seconds recovery.
  • After the last set, skip straight to cool down.

Cool Down:

  • Spin easy for 4 minutes.


The primary goal is to Improve maximum aerobic capacity (power that relies on high levels of oxygen uptake) by pinpointing repeatable 40-second power and fully stressing your aerobic capabilities in order to improve them.

Limited recovery within each set keeps aerobic uptake very high meaning that each subsequent 40-second effort will start at a higher percentage of oxygen uptake and yield even more time near peak aerobic power.

This workout affords an opportunity to accumulate a lot of time at peak aerobic output in order to improve power at VO2max and perhaps even VO2max itself.

Try to keep your cadence high, above 100rpm during each interval, but if fatigue forces a lack of control at higher cadences then slow things down a bit and ride smoothly.


That would be a ridiculous workout to do outside. I wouldn’t worry about the tiny power fluctuations or power in general. Just stop on the pedals and settle in to roughly that area of power. Also, just do the warm-up block of 30/30s and then the blocks of 40/20s.

Personally, I’d rather find a VO2max workout that gives you longer intervals with the same time in zone, like 4 x 5 minutes. That would certainly be easier to execute.


Am I missing something in not doing these short intervals?

It depends on your goals – if you are focusing on crits, for example, shorter intervals like those found in Merced -2 can be useful in getting used to going hard and recovering over and over again.

How in the heck can anybody execute a 20-40 second “on” interval outside?

It can be difficult to nail the target power exactly as the workout prescribes, but if you can at least keep in in the VO2 Max zone range, you’re on the right track.

Focus on pushing hard, but not too hard. “Pinpointing repeatable 40-second power” is a key phrase for workouts like these ones. Ideally, try to aim for, say, ~330 watts every time vs. hitting 500 watts for 40 seconds on the first one, then 400, then barely able to hold onto 300 (trust me, I’ve made that mistake before :sweat_smile: )…

It takes some practice, but it is certainly doable!


Honestly, from what I have seen. TR really needs to look at their Vo2 max workouts and maybe reconsider what they offer and why. There is a time and place for that workout, but a 5 x 40/20 is probably not the best for increasing Vo2 max.


only if you don’t have control… If you have control then 40/20s are fun to do on rolling terrain:

Absolutely, even 20/40s !


I’m using Plan Builder to train for a century. It’s hard for me to see how intervals like Merced -2 are useful for that purpose and seems like I’d be better served with longer intervals.

This is essentially what I’ve been doing. Easier to execute and seems more applicable to the century ride I’m training for.

specificity is important to train before an event - but to build a well rounded cyclists all training zones should be trained throughout the year at some point (in a thought out periordized scheme)

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I said just do 30/30s and 40/20s.

The workout is ridiculous because 20 seconds rest, 25 seconds rest, 30 seconds rest … why? Other than mental indoor trainer fun?

I also don’t think the increasing watts on the 30/30s and the decreasing watts on the 40/20s makes any sense other than to make it more interesting as an ERG mode ride.


Why? Because that’s a priming set in the warmup.

As has already been mentioned, specificity for your goal matters. If you’re training for a flat century, I would definitely change it to a 4x5 or 5x4 type VO2 workout.

Crits were mentioned above as a place where 30/30s are helpful. Another is MTB, if you’re riding in a place with lots of short punchy uphill sections. We have a local section called Roller Coaster, and 30/30s are perfect for that.

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5 seconds isn’t going to make one bit of difference. Nobody ever did workouts like this prior to indoor erg mode becoming available. This stuff is just extra fancy.

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As said above the beginning is just a warmup, whether you’re inside or outside doesn’t matter if you pick the right road outside. IMO
The warm up for these are good to gauge what cadence and power you might be able to repeat for the workout. That’s how I used them, others may be different.
If you don’t like something you can pick something else that looks fun. It might not make that much of a difference unless you’re a couple months from an event.


The century I’m training for has ~6500 feet of climbing, but the climbing is sustained. I’m also coming from a weight lifting background (many years of competitive powerlifting) and so generating high power for short periods is something I’m pretty good at already. I get that doing that on a bike is different and that repeated efforts with short rest like this workout are also very taxing, but I’m about two months away from my ride and the Merced style workout just doesn’t seem like the best place to spend my VO2 Max training day right now.

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How did you describe your event to PlanBuilder? The VO2 intervals in the sustained power and gran fondo plans are all longer efforts. Seems like you’d pick those in prep for a century.

IIRC, the gran fondo plan used to be called the century plan.

I told it how long I anticipated the ride would be (7 hours) and that it was a Gran Fondo. I then picked the Masters Low Volume Plan. Plan Builder gave me:

Masters General Base I (4 weeks)
Masters General Base II (4 weeks)
Masters General Base III (4 weeks)
Masters Sustained Power Build (3 weeks)
Masters Gran Fondo (1 week)

This is my first experience with TR, so I just let Plan Builder do its thing based on what I told it about the ride I’m training for.


Ah, you’re still in general base if you’re two months out as build and specialty are truncated. That makes sense. It doesn’t look like there’s a different base phase with long VO2. The substitutions you are doing might be the only option.

FWIW I like polarized base and it’d work well outdoors. But it doesn’t have VO2, only threshold.

@WindWarrior those intervals up there are a thing of beauty.


Polarized base looks good to me. I may give that a try after my century.

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