Why is my VO2 Max / Cardio fitness dropping?

57 years old, always been moderately okay fitness-wise. For as long as I have bothered to look, my CO2 Max fitness has been around 34/36 (which is ‘Above average’) but from June onwards it has steadily been dropping, despite my making changes in my schedule so I can get to the gym three times a week now (it was just once before) – sessions are a mix of weights, classes (usually ‘Spartan’ type of classes with weights/resistance mixed with spin bikes/rowers/ski machines etc) and I usually do a one-hour high-intensity spin session once a week (keeping my heart in ‘tempo’ zone for as much as I can). Strava is telling me that my fitness is now the highest it has been for over two years (no idea what metric they use to get to this) but my Vo2 Max is now down to 32 and steadily getting lower. I know it shouldn’t bother me, but I am getting all these ‘Your heart health is below average’ messages and they wind me up. Am I dying? Have Apple changed something? Do I just need to get a life?

Are you over training? Getting enough rest? Stress levels on the rise? Getting enough sleep?

Apple explanation of how they do VO2 max: https://www.apple.com/healthcare/docs/site/Using_Apple_Watch_to_Estimate_Cardio_Fitness_with_VO2_max.pdf

Maybe it’s measuring your reaction to exercise but doesn’t know you’re carrying a weight or whatever so thinks you’re more knackered than you were before.

I get plenty of rest (in that I don’t have an active job so I have lot of inactive time – I do get ), stress is no worse than it ever was, just like sleep. I don’t feel like I am over-training as I don’t feel fatigued between sessions and always feel good to go when I am there. I assumed my VO2 Max would increase (in the past it always has done) when I exercise more.

Im not sure Ive read your post quite right but I don’t see much moderate / easy Zone 2 riding in there which is what you need to do long term to build your Vo2 up with sprinkling of intensity. You may be overtraining even on a low volume. There are  no end of videos on YouTube about zone 2 but I like Bulletproof Cycling and his no nonsense approach to training. I’m sure he’ll have a good one on Zone 2.

Making more time for strength training are you spending less time at intensity than previous?

Mine has dropped since season finished and focus shifted to endurance.

How are you actually measuring your VO2 max?

How are you actually measuring your VO2 max?

I take the actual number with a pinch of salt tbh, WKO5 has me at 57, Garmin at 70…both have access to roughly the same data set.

But you can still monitor the trend.

I guess there’s fitness and there’s fitness. What does your watch tell you about your cardio stress score over time and has that changed in the last few months? Has your time in zones changed much over the same period. I wouldn’t be surprised if yoour VO2max might e dropping if your intensity has dropped a little over time. Worth taking a closer look at that kind of info to get a sense of what has changed in relation to effort and health, and how that works in relation to your individual sessions. Or if you are only doing a HIIT spin class, you might be doing too much in high zones and DickB’s overtraining question is very relevant, and maybe you need to add in some more Z2 efforts during the week.

Zwift Insider Tiny Races on Saturdays, a quartet of very short races back to back, starting at 0900 / 1500/ 2100 GMT. One other day per week involving high intensity reps should help improve VO2.

Vo2 Max naturally declines with age, not much you can do. Our yearly fitness test is based on Vo2 Max and the Service Fitness bloke reckons HIIT style training is the best to increase it, heart rate up, recover, back up, recover, etc.

I’d also take the Stava/Garmin/Blah readings with a pinch of salt as my work score has been high 40’s, low 50’s for the last few years where as Garmin reckon low 40’s.

but I don’t see much moderate / easy Zone 2 riding in there which is what you need to do long term to build your Vo2 up with sprinkling of intensity.

I do plenty of dog walking which should cover that off – I tend to push myself a bit more when I am at the gym.

https://youtu.be/GzXkaTUcR24?si=WSldOF7Cm22Nce8a

Garmin, Apple, something else?

How are you actually measuring your VO2 max?

Garmin, Apple, something else?

Apple Watch – had the same one for about three years I think, the VO2 Max has always been sort of steady so just a bit confused as to why it is going down when my notional fitness is going up. I know it isn’t going to be 100% accurate, but I’d expect it to give consistent readings.

What’s your heart rate done in this time?  Plus you’re doing more strength and light on aerobic work

What’s your heart rate done in this time? 

It’s stayed pretty static – same as it has always been really.

I’d be looking for some info over the course of this year looking at time in zones and cardio stress versus tolerance and see if there’s anything going on there.

Does Apple give you any charts like these?

Another armchair coach here and my guess would be exercise done mostly at high intensity and too little at steady z2 pace causing drop in VO2.
Now VO2 isn’t a marker of overall fitness but only one aspect of it, you might be fit and strong otherwise but just your fitness in endurance sports is decreasing as you are focusing in strength and high intensity.
Nothing wrong with that, adding variety to training helps with avoiding burnout and endurance training can be focused on in spring when weather is nicer.