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Garmin VO2 estimate drops on slower runs.

Tangmu
over 4 years ago

I’m 62, male.  I’ve been running 3 years.  Best 5k is 34 minutes, best mile 9:39.  I typically run/walk about 2.5 miles 3 times a week.  Running pace is about 9 minutes, and overall pace is about 11 minutes, including the walk segments.  I’ll be in Zone 4 about 60-70% of the time, the rest Zone 3 (mostly the walking segments).  My HRmax is set at 170 on the watch.  The highest HR I’ve seen training is 163.

Garmin has my VO2 max estimated at 43.  It’s been pretty steady for 6 months.  Runalyze has my effective VO2max at 34.1, which is my highest ever.

Twice in the past I’ve decided to run slower and continuously.  That’s about an 11:30 pace.  Mostly low end of Zone 4, with a little Zone 3.  When I’ve done that, Garmin drops my VO2 max estimate dramatically.  My Performance Condition will show like -7 or -8, and status Unproductive.  (I know both of those just reflect the declining VO2 max).  This will go on for weeks, then I’ll go back to running faster and my VO2 max will go up again.

Today I went for a slow continuous run after months of my usual run/walk, and got Perf Cond -8, status Unproductive, VO2 max down 1.2 points according to Garmin.  Same as the last two times I did this.  Effective VO2max up 0.1 on Runalyze.  I know from my previous experience VO2 will continue diving as long as I run slower.

Doing a slower training run shouldn’t pummel my VO2max, should it?  What’s going on?  From what I’ve read, it’s good to have some slower runs and not train fast all the time. 

  • 0 over 4 years ago

    It is. But the way I've thought about it is that the VO2 max it's reporting is the value from that data, not what you'er totally capable of - so if you coast a bi it will decline. The best indicator for me, and with runalyze you can chart it, is look at average HR per run.

    As a resuI tend to factor in slow recovery runs in-between faster runs, helps keep the impetus going

  • 0 over 4 years ago in reply to Ɛpsilon

    Oh how are you defining your HR Zones? If you have a strap, do a Lactate Threshold test - I find that seems to be the best way to define the zones 

  • 0 over 4 years ago

    If your zones are not right then the computation will be all screwed.  I've had a strap go insane on me before, feed bad data for a bit before I realize it (usually after I get a couple implausible results for lactate threshold and such), this skews the VO2, and it takes a while after I replace the defective strap until it comes back to reason.

    Without knowing where the lactate threshold the VO2 is a guess and makes too many assumptions, so what you're seeing does not surprise since it can only work with the data it has.

  • 0 over 4 years ago in reply to Ɛpsilon

    "do a Lactate Threshold test - I find that seems to be the best way to define the zones"  Thanks for that idea.  I have it set on Auto and the watch has reported a lactate threshold a few times.  I'll let it set the zones based on that and see what happens.  

  • 0 over 4 years ago in reply to Tangmu

    It works for me. Because it relies on Resting HR and Lactate Threshold HR - both of which it can measure - rather than Max HR (which you provide and may not be accurately got) I find it gives me far more acceptable HR coverage in the zones....


  • 0 over 4 years ago in reply to Ɛpsilon

    Since doing that I do a lot of my slow running in HR rather than Pace and it's helped me get my VO2 up no end :)

  • 0 over 4 years ago

    So, you go and run in a HR zone that is (relatively) unfamiliar to you, and you're surprised that you don't perform well in this zone?

    [Apologies for the snark.]

    More seriously, with most of your running in zone 3 and zone 4, it sounds like your aerobic energy system is under-developed. And that is what the lower numbers from running in zone 2 right now is telling you. Building an aerobic base by running slowly is actually the key to increasing fitness and running faster. Unfortunately, the aerobic systems are slower to respond to training than the anaerobic systems - it takes several months of zone 2 running to build this base. It can be seductive to pursue the faster responding but limited gains of running in higher HR zones - even if the aerobic base route may end up making you a faster runner overall.

  • 0 over 4 years ago
    tickerguy said:

    If your zones are not right then the computation will be all screwed.  I've had a strap go insane on me before, feed bad data for a bit before I realize it (usually after I get a couple implausible results for lactate threshold and such), this skews the VO2, and it takes a while after I replace the defective strap until it comes back to reason.

    Without knowing where the lactate threshold the VO2 is a guess and makes too many assumptions, so what you're seeing does not surprise since it can only work with the data it has.

    Actually, how your zones are set has nothing to do with VO2Max. The algorithm uses % of MaxHR as a key input into the VO2Max (which is why a chest strap measurement spike can mess with this) - zones aren't used.

    Don't get me wrong - knowing where Lactate Threshold is and your zones is important, especially for the classic 5K and 10K distances. But zone setting doesn't impact the VO2Max calculation.

  • 0 over 4 years ago in reply to mcalista

    https://assets.firstbeat.com/firstbeat/uploads/2017/06/white_paper_VO2max_30.6.2017.pdf

    Interesting. Odd that I've found my values more believable when I used LTHR for my zones mind. But I'd have thought theyt'd have used something better than MaxHR :) !

  • 0 over 4 years ago

    I was having a similar issue as well until I switched to lactate threshold. In my case it increased my zone 2 up to a max of 142 bpm. Once I started doing my longer runs in strictly zone 2, my V02 max number started to increase steadily and I felt my endurance increase along with it.