Training Question VO2 intervals

When performing VO2 intervals, should my HR drop down into zone 2 before starting the next interval?

I performed the step by step work out and it has 90 sec of 110% FTP followed by 30 sec rest then repeat X 5 reps for 2 intervals.
My HR did not drop to zone 2 between the reps so I’m wondering if I should do a costume modification to give me more rest between reps.
My HR did drop to zone 2 during the longer rest interval between the two VO2 intervals.

Not if you’re only getting 30 seconds of recovery, it shouldn’t. Those short recoveries will just allow your aerobic system to reduce some of the oxygen debt built up in the preceding interval(s), so you should expect to still be breathing hard and for your heart to still be working pretty hard.

If, on the other hand, you’re doing something like 4 × 4 minutes with 4 minute recoveries, you want to be ready to go again and produce a good interval every time. In that case, heart rate should drop commensurately (likely down to Z2)

But don’t overthink it!


I like to try to NOT over think it,but Zwift workouts have a history of not being thought about enough.
Many work outs are very hard but that’s all they are.
They are hard with no specific reason or goal for the added intensity.

I guess I am asking a more general VO2 max question.
I get “time in zone” is the important issue but is rest between efforts an important issue.

What’s the difference between 8 X 1 min efforts vs 2 X 4 min efforts?
The Power will definitely be different.
What is the definition of a 1 min VO2 vs 2 min vs 5 min?
They feel really different. Are they?
And should the rest period be important?

I’ve not put much thought into it for the past 4-5 years and I’m kind of stagnant.
Maybe that the best a 60 year old that rides 4 days a week for a total of 5-6 hours per week can expect.
I’m sure that last part, 5-6 hr per week vs 10 hr per week also plays a role in it.

What is constant, I find this is fun.
I like riding my bike and I enjoy training and seeing if it makes a difference and even if I find out in 2 years, nothing has changed, I have been riding and mentally engaged in cycling the whole time.

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If nothing else, you improve at what you do, so if you do, say, 2 or 3 sets of 5 1 minute VO2 Max efforts with 30 second rests you’ll get better at repeated hard(ish) efforts on minimal recovery.

Will you actually improve (or slow the natural decline in) your VO2 Max? Probably not. For that you need to do longer intervals (2 mins minimum) switch off erg mode, lift your cadence and hang on as best you can while your breathing goes ragged and your heart rate flies up. Let the power drop throughout the interval. That’s fine. Pedal super easy through the recovery interval and do another one. And another one. You get the idea. Aim for 15 to 25 minutes TiZ. You can use The Gorby as a template. The recoveries would normally be the same length as the intervals, but taking an extra minute if you need it is better than being a slave to the beeps and not producing good work.

Done properly, it is really unpleasant. If you’re not motivated (chronically or acutely) then don’t even think about it. I can knock out an hour of sweetspot even on meh days, but I need to feel really good to do VO2s, and even then I find them super challenging.

Are you doing the intervals with ERG on or off? Since they should be maximal efforts you’re better to do them in slope mode and really go for it. Some days you may not hit the targets but other days you’ll surprise yourself and blow through them.

I’d also consider the 1min intervals to be anaerobic capacity and not Vo2 efforts. For those you’ll often hit 125-150% of FTP (or maybe even more). Which again is why you want ERG off. They’re going to hurt but the gains are worth it!

I have a dumb trainer with a power meter.
Yes , many of my shorter intervals are anaerobic.

If riders are following a 5-6 month off season schedule, then Dec and Jan is a lot of base and there was a lot of talk about Zone 2 stuff.
Now we are nearing the end of Jan and it’s time to introduce intensity so now VO2 questions come up.

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For old uns (shout out to the 50+ posse) it makes sense to sprinkle in VO2 work pretty much year round, just to fight the natural decline in VO2. One workout in each of weeks 1 and 3 if you’re training 3 up 1 down should do it.

Obviously you can do a focused VO2 Max block when you feel you want to try to raise the ceiling and increase your VO2 Max. As and when I get my TTE at FTP out past 50 minutes I’ll consider a dedicated VO2 block. Maybe. :wink:

I pretty much use MTB rides for this purpose.
Of course, o beautiful Spring and Fall days (or windy Summer days) I will MTB more instead of road rides.

I’m lucky.
I can Road ride or cross country MTB out my front door.
I can also throw in kayaking and sailing and cross county skiing if it snows.

Illinois. Go figure.

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