Lower Vo2 max after starting a new Base Phase?

Hi, I have been using TrainerRoad for quite some time and use it more and more now I have understood the benefit of continued structured intervals instead of just hammering outdoor rides with no rhyme or reason.

Last year I followed a sprint triathlon plan and found my ftp generally increasing as the training progressed from around 260 to 274 using the ramp tests throughout. I also watched my vo2 max estimate on my Garmin rise from around the low to mid 60s.

Following my local A race at the beginning of August I took a few weeks of unstructured riding, running and swimming while on holiday. I then returned to trainerroad for some structured workouts once more. I am around 3 weeks into the half distance triathlon mid plan so have not tested via the ramp test since before my holiday in mid August (274ftp), but have noticed that my Garmin is dropping my vo2 max estimate from a high of 65 to 59 as of today.

I don’t know whether this is normal in the base phase or shows a drop in fitness, that I should address with a change in plan. My feeling is that the rides being fed to the Garmin are now of a more aerobic nature and my estimate is lower because my aerobic endurance is of a poorer level than the vo2 max workouts I have become more accustomed to during the sprint plan.

If anyone has any experience of this or has any thoughts I would be much appreciative in hearing from you.

Happy to provide any additional info if needed.

Thanks for reading and any help you can provide.

1 Like

So, I think it’s now five weeks (two holiday, three into the new plan) since you tackled anything like VO2 max work?

If so, that’s plenty of time for you VO2 max numbers to drop. I know nothing about the Garmin measurement/reliability but I’m almost certain that this was discussed in a recent Podcast.

You can make significant VO2 max gains in a focused 4/5 week block but unfortunately, if you don’t continue to ‘sharpen’ those gains with a regular workout, you’ll lose them just as quickly.

If you have the time and fitness, you could add an additional VO2 max workout to each week of your plan. This is what I intend to do during my winter base training.

You need to feed the Garmin with effort(s) of VO2max duration, otherwise the number drops gradually. It always goes down for me when I do endurance / recovery rides or during rest weeks, that does not mean my VO2max capabilities went down though.

The estimate has its’ flaws, don’t take it seriously.


Hi PusherMan,

Thank you very much for your insight. I see the 2nd 4 week block of the medium half ironman base plan has some 2-3 minute repeats at around the 120% FTP, so hopefully that will start to address this while trying to grow my durability needed for longer durations.

I did feel that by not working these types of intensities that I would ultimately reduce my ability at these intensities.

On weeks 2 and 3 I substituted the sprint workouts, but used one where it was 30 seconds at 225% FTP which were right at the edge of what I could handle. The prescribed ones were 20 seconds at about 150% FTP I think. Hopefully these will give me room to grow when I get to some vo2 max intervals.

Hi bagr84,

I wondered about this as the Garmin is only able to calculate this estimate from the types of work that I am feeding it. Interestingly the vo2 max estimate for running is sitting pretty much bang on where is has been for about a year now, at around 57 or 58. My running program is less structured and generally goes on the theory that I will do a harder tempo run, a vo2 max type interval session and a longer easy run each per week. I tend to decided when to do each based on how I am feeling, and is probably quite consistent.

I know I shouldn’t put too much on Garmin’s estimate as sometimes it says I am being unproductive yet I am seeing some gains in FTP at the same time, and that FTP is somewhat more measurable and repeatable than the vo2 max estimates.

My main worry was that I was not doing the correct types of training that my body best responds too.

I think I will do the 4th week of the plan, ie the decreased load week and then retest my FTP using the ramp test and see where it lands. I do expect a reduction but hopefully not by too much.

Thanks guys for your input here. It is really appreciated.

I believe Garmin indicates your VO2Max as declining if you’re not working aerobically meaning your training effect is below 2.0 aerobically or something. If you’re using a device that measures training effect that is. Otherwise it might just do calculations as usual when you do sustained efforts near or at FTP. I always get a raise in VO2Max when I do 5mins or longer at 88-94% FTP.

this - if you don’t run hard for a while it will naturally drop. thus, the drop is irrelevant as it has no physiological correlate.

Hi Grenhall and Schmidt.

As I understand you I shouldn’t really pay too much attention to the Garmin estimate as I can effectively alter it with the choice of workouts I do. This might be why following mostly a sprint based program of workouts that favour efforts near or above ftp would give me a higher value than the more aerobic based workouts from the medium volume half ironman distance training plan.

I am working on the Medium distance half ironman plan just now as I would like to build my endurance for longer durations and felt I can increase the duration by backing off the intensity until the build period.

Hopefully this will give me the results I am looking for. Time will tell I guess.


Same experience, I drop a few points when going for restweek/base training.

I don’t think so… it seems to be linked more to avg power/pace:hr. My vo2max readings have gone up after an endurance ride. I haven’t really been doing much VO2 max efforts since short power build, and the number has been steadily going up throughout the summer. When I do VO2max efforts they are also longer, 6-9 minutes, so lower in power, but I’m not sure that the TR workouts affect the VO2 max readings, in the same way that they don’t calculate a training impulse from them either.

Mostly mine drops for running as the surface I run on is slower during the warmer months… I got dinged from my HIM yesterday, it dropped me down 2 ml/kg/min after that run since I had checked after my last run during the taper. I guess it’ll bounce back as long as I don’t loaf off too much after this race.

Hi Ecto,

Thanks for letting me know this happens to you too. I don’t normally bother too much as I have seen drops and gains like this too. It was the size of this drop that was more concerning to me.

Hi Bioteknik,

Your experience is interesting as it kind of sits with my original thought but also with the other comments received on this topic in that the garmin vo2 max figure is definitely feeding from the type of workouts being done and how it calculates your fitness based on these inputs.

From all the comments received so far I would presume that my vo2 max may have fallen a little bit as I have not been as much vo2 max work but that it probably isn’t as much as what the watch is stating. I think that endurance is one of my limiters and that a solid block of longer duration workouts will likely start to improve my aerobic system by benefiting from the greater volume of training that I am able to tolerate by decreasing the overall intensity.

Hoping that the measure will show improvement like yours Bioteknik once I am a bit further into the plan that I am currently on,

I do feel that the medium half ironman base plan is challenging enough for me, although am finding that the mussels are not quite as affected as they were doing the sprint based plans with the higher percentages of ftp required.