Time in Zone vs. Structured Intervals

Curious about accumulated time in zone over the course of an outdoor ride versus structured intervals on the trainer.

This weekend, I did a 4hr/250TSS group ride on Saturday and Sunday I did Spanish Needle -3. When I compared the two rides, I noticed time in VO2max and Anaerobic zones were virtually the same on the two rides. This got me to wondering if I accomplished the goal of Spanish Needle -3 on my Sat group ride and therefore could’ve replaced it with another, more enjoyable, group ride and still feel good about hitting my weekly marks?

If the answer is yes, is this true across the board or are there some workouts that crossover better than others in this regard?

The answer is Yes. And yes, it is true across the board.

The caveat, of course, is time efficiency, and from my experience the 3:2 ratio holds about true - 3 hours outdoors to achieve 2 hours worth indoors due to generally longer warmup and cool down periods, downhills, and travel between interval locations. The exception is the endurance/fat burning ride where the ratio is closer to 1:1.

In addition to the enjoyment vs time efficiency consideration, there are other factors that may influence your decision. I find it easier, for example, to put myself through 4x20min SS on the trainer (vs doing outdoors). However, conversely, when I need to go really deep, our weekly climbing sufferfest (8-12 hills of VO2Max and above) is easier for me in a group suffering format than solo on a trainer.

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At what point does the duration of intensity in an effort become a factor in the quality of the work done? Spanish Needle is not a good example with it’s microbursts, but you could do an outside ride and accumulate 16 minutes of Vo2max with little bursts into Vo2max for a handful of seconds at a time, but i would not have thought that was effective training in the way an 2x8min intervals at Vo2max would be. Am i wrong?

Quality would be based on your control of power, regardless of duration. I’ll assume CoP will always be of higher quality on a trainer because there are almost no environmental factors, e.g. hills, wind, road surface.

The answer is no.

The aim of Spanish Needle is not just to accumulate time in the vo2 max and anaerobic zone, but to do it repeatedly with only 15 seconds recovery between each one. It should take a serious toll on the aerobic system too.

Across a 4 hour ride the 20ish minutes over 140% would have been much more spaced out, allowing for more recovery, meaning that the next anaerobic effort will hurt less. Worth pointing that you easily go into zone 6 pulling away from stop lights…

(This isn’t to say you can’t achieve the goals of Spanish Needle -3 on an outdoor ride - just that you almost certainly didn’t)


Spanish needle is an aerobic ride as much as anything else. While the individual efforts are anaerobic, their short nature with limited rest makes the overall interval and aerobic one.

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Structured TiZ will outperform unstructured TiZ from an adaptation standpoint.

60 minutes of threshold in 4x15 with short rests > 60 minutes of threshold accumulated throughout a 4 hour ride

20 minutes of VO2 work in a 4x5 session will massively outperform 20 minutes of VO2 accumulated in a 2-3 group ride.

Group rides have their place and their own unique benefits (especially from a “race brain” perspective), but they are very poor substitutes for structured training if you are looking to drive improvement in a particular energy system.


During the base phase, it is more about time in zone.

As you progress through the build and specialty phases, it becomes more about repeatability, and the length of the intervals and the shortness of the recovery intervals between them takes on more significance. In a group ride, you won’t have much control of the intervals or recoveries, and it is unlikely to offer the benefits of structured intervals on the trainer.


I’d say hell no it’s the same.

Duration and recuperation of an effort at a specified zone vs accumulating time there doing random riding doesn’t feel the same for your body.

The most clear example is vo2max workouts.

If anyone is to ask me my cycling strengths, I don’t reply “sprinting” or “time trialling” but “sneakily getting group rides to knowingly or unknowingly indulge my training protocol”.


I think what MartinHeadon said is correct. They aren’t equal. Unless you were replicating the same workout on your group ride they are different.