VO2 Max Interval Workout Substitutions

Tomorrow I have Kaiser planned as my VO2 session which is 6x3 min 120% with 3 min rests between each interval. Last week was Spencer which is nearly the same as Kaiser but one less interval. I struggled to complete Spencer and added a few more minutes of recovery before the last two intervals.

So my question is, is there a variance of adaptation that will occur if I substitute Kaiser for Dade -1 which has 3 sets of 3x2 min 120% with 2 minutes of recovery between intervals, and each set has a 6 minute recovery afterwards. Both workouts have 18 minutes at 120% but one just adds more recovery. Is the variance less than say, a workout with 3 mins at 120% but longer rest between like 4 or 5 minutes?

You’re stronger than you were last week.

Just do it.


The struggle was real haha. I felt very lightheaded and cadence would just fall off a cliff with 30s to go

If it were me, I would repeat Spencer and if I could complete it as planned (unlike last week) would skip off feeling pleased with myself afterwards, and more confident about the next workout…

1 Like

I guess my question is more asking about time at a certain percentage yielding the same adaptation regardless of rest duration.

Two suggestions if you’re struggling with VO2:

  1. Do Huffaker - it is a good baseline Vo2 workout. If you can’t complete it, you’re going to struggle with any Vo2 workout. Keep at it until you nail it, and then move up.

  2. Anytime you don’t think you can make it - bail out of the interval for 10-but-no-more-than-12 seconds (Chad has covered this in podcasts before and IT WORKS). Don’t let your heart-rate start coming down - which it will if you go longer than 15 secs. You’ll still be tasting metal in your mouth and will be able to hear your pulse in your ears, but your muscles will slightly recover before your aerobic system knows it doesn’t need to supply as much oxygen…and then pick it right back up and finish the interval. If you do this, go all the way to the end. Don’t bail on the workout – just bail on the intervals for 10 secs at a time.

Pain is weakness leaving the body.

Good luck - you got this!


It will yield a different adaptation but still be useful. However, if it was the 3 minute intervals I was struggling with, I would personally want to revisit that particular effort in order to keep my self confidence up rather than reduce to 2 minute intervals. As mentioned above, even if you include a short 5-10 second backpedal.

An example not based on VO2max efforts - doing 3 x 20 Sweetspot efforts definitely has a different effect than 6 x 10 SS efforts but most importantly for me it is the ‘knowing’ that I can get through the 3x20 that makes me believe I’m stronger, which I’m pretty sure reduces RPE in future workouts.


Makes sense. I’ll likely try to complete the 6x3min workout and see how I feel. Another thing I thought about, if you increase recovery time to 10 minutes it makes everything easy, so there is definitely a difference with the shorter recovery valleys.

I would do Kaiser at 110 or 115%.

1 Like

There is no substitution for VO2max! :smiling_imp::stuck_out_tongue_closed_eyes:

I hadn’t thought about Huffaker in this way, but I think you’re right about it being a baseline VO2Max workout. I would add that even this you could reduce the intensity of the workout by up to 4-5% and still be getting the intended training benefit. Below 95% intensity, I would start to question if your FTP is set too high.


Getting on-top of the gear for VO2 max intervals is crucial.

i.e. not rocking up to the work interval from the recovery valley with a cadence you might use for slow force work!

Having to create an extra 25-30 rpm to lift yourself back to that 90-100 rpm range is going to zapp any punch out of your legs pretty quickly at 105-115% of FTP.

Not only this but cruising in at 90-100rpm means the first 20-30 seconds of the interval will hurt a lot less than they would otherwise.

For me a VO2 max interval starts 15 seconds before the recovery finishes.

Spinners are winners.


I found that technique to be very helpful too. Spin up to 100-110 a few seconds before the interval hits. In my case, I would struggle with the last 30s though. I am training for a fairly demanding ride up some hills so I will need to really work on my 3-5 minute power. Outside it still seems easier.


Consider adjusting your gearing too.

I rode either a semi-compact or compact on a 28t for about 3 years. Perfectly manageable but on some of the grades around here it made things unnecessarily muscular when that wasn’t the purpose of the ride.

I put a 32t on for a trip to Spain, for shallower but longer grades, and kept it on ever since.

Power output isn’t any different but that extra 5-10rpm makes a world of difference for longevity. When out of the saddle unless the pitch is over 20% it can still feel quite comfortable.

Unfortunately I’m limited to 30t rear with my current derailleur. I may put on a 34t inner ring and hope I can shift to my 52t big ring. That’s about all I can get without totally changing my drivetrain. Right now on these hills I’m spinning around 55 rpm on 30% grades.

I had the Mills VO2Max workout today. What I “liked” about it was the 2 minute intervals were descending after the first 45 seconds at 120% and then 1:15 down to 110%. I was able to finish the workout and felt like it was a good one. Something to consider.

Note that the warmup is very quick - only one minute.



Just looked at my VO2 workouts and my average cadence for the intervals was ~108 rpm (low 96, high 134).

Remember, VO2 intervals are for developing cardio, not muscles. Do not grind!
Put the stress on the heart and lungs, not the legs.


Thank you! I needed to be reminded of this!

How did this end up? I found this post because I was about to ask the same question and was redirected here (pretty cool feature). I had to backpedal during the last 2 intervals of Spencer today. My HR hit 194 and I was in a world of hurt.

1 Like

So, I decided to go ahead and try to do Kaiser (6x3min at 120%) and my legs would immediately flood. I made it 3 intervals before quitting. I thought maybe my ftp setting was too high but not long after testing it I did 3x16 over-unders and it felt actually kind of easy.

My best guess is that I haven’t done efforts like these in a while and that I’m building my base into my ceiling and the gap is closing moreso than earlier this year when my ftp was lower but VO2 Max was well above 120%. I could probably stand to take a rest week as well.

Looking back I would have liked to do the 3 sets of 3x2 minutes. I think that third minute really puts me in a bad spot.