VO2Max with Indoor Cycling

My understanding is that speed is not used to estimate your cycling VO2Max (it is used for running VO2max). For cycling VO2max, the power and heart rate data is used. The ICG Training bikes used in in gyms for example do not transmit any speed or distance data (as it is really meaningless on an indoor bike) and only transmit cadence and power but the Fenix uses this to calculate your FTP threshold and VO2max.

Yes, only power & HR are used to calculate VO2 Max. Be aware that most rider's power output will be lower on an indoor trainer than an outdoor ride (there are various theories surrounding this), so you may see a drop in your VO2 Max (and FTP) as your indoor training increases relative to your real world riding over winter or whatever.

I do the same as you for distance, record the workout on my f5 but then edit it with the distance from Zwift. However, you can still get the f5 to record a reasonably accurate distance by setting a virtual wheel size. Go to Settings>Sensors and Accessories, Spd/Cad Tex Neo (or whatever you've called it)>Wheel size and set it to something like 2500mm (don't set it to automatic). Once you've completed your first ride, note the distance recorded on the f5 (f) and the distance recorded on Zwift (z). Then work out z/f, multiply it by your wheel size and set the result as your new wheel size. You may have to do this 2 or 3 times to fine-tune it, and you'll never get it spot on, even during a ride the values will float either side of each other, but at the end of a 60 minute session my fenix now shows a distance which is within a couple of hundred meters either side of what Zwift's saying.

OK - that makes sense and thanks for the tip NeilJonesOnline :)

I still think VO2Max is totally off for one reason or another.
Any idea why the graph is full of "missing values"? All my rides include power/HR.ciq.forums.garmin.com/.../1253099.jpg

I get those gaps in my graph too, no idea what it's all about. Personally, I think my VO2Max is pretty spot on, it's about 5 points down on when I had it properly measured about 10 years ago which seems about right. Sometimes one ride will seem to skew it, but then within another ride or too it's back to normal.

But as I mentioned above, if you don't have a power meter on your bike and you're only measuring power (and therefore VO2Max) when you're on the Neo, then your power is likely to be lower and therefore so is your VO2Max. For example, my FTP on an indoor trainer is at least 10% lower than my real FTP - or put another way if I try to cycle at my real FTP on my Tacx, I'm dead within minutes. That's not down to an inaccuracy of the Neo (or any other trainer), it's just a phenomenon which people suggest is related to the fixed position of the bike limiting which muscles you use, lack of airflow meaning you're warmer, the 'boredom' factor, phase of the moon, price of cheese etc etc - take your pick.

Hello,

I use the Neo smart with the tacx training app. I use it with slope to zero therefore speed matches more or less speed on road or with a fiz wattage, in that case speed can go up to 50KM/h, easily. The power is always from my stages PM. I notice the same VO2 indoor is always 4 to 5 points less. Personally, I think that is due to to heart rate that is a bit more at same power, due to the heat.

Regards,

A. Duarte

Yes, only power & HR are used to calculate VO2 Max. Be aware that most rider's power output will be lower on an indoor trainer than an outdoor ride (there are various theories surrounding this), so you may see a drop in your VO2 Max (and FTP) as your indoor training increases relative to your real world riding over winter or whatever.

I do the same as you for distance, record the workout on my f5 but then edit it with the distance from Zwift. However, you can still get the f5 to record a reasonably accurate distance by setting a virtual wheel size. Go to Settings>Sensors and Accessories, Spd/Cad Tex Neo (or whatever you've called it)>Wheel size and set it to something like 2500mm (don't set it to automatic). Once you've completed your first ride, note the distance recorded on the f5 (f) and the distance recorded on Zwift (z). Then work out z/f, multiply it by your wheel size and set the result as your new wheel size. You may have to do this 2 or 3 times to fine-tune it, and you'll never get it spot on, even during a ride the values will float either side of each other, but at the end of a 60 minute session my fenix now shows a distance which is within a couple of hundred meters either side of what Zwift's saying.

I set the wheel size as you suggested to 2500mm and much better now. It is 2.2% off which is not that bad!
Anyway, if I get it right, the speed/distance is not impacting the Cycling VO2Max while indoor?

ciq.forums.garmin.com/.../1253373.jpg

Glad that worked for you - 2.2% sounds about as good as you'll get (it will vary ride-to-ride), so you might want to just leave it at that - I've just checked and I've got mine on 2560mm. A couple more rides and you should have a good enough idea whether it needs tweaking (e.g. if it's always over or always under).

And yes, this has no bearing at all on your VO2Max.

The "virtual wheel size" set for the Tacx Neo Speed/Cadence largely depends on the Zwift elevation profile. You're fine with ~2500 for a flat course to get a good match with Zwift. But to be honest that all means nothing because the speed on Zwift is always (much) higher than achieved outdoors. I think it's more realistic setting the wheel size to something close to the wheel (e.g. 2130). This all of course does not have an impact on VO2max Cycling estimate but wouldn't it make sense getting rid of those ridiculous speeds/distances obtained from Zwift?