How long time for Vo2max to settle?

Hi

1. VO2MAX calculation is not also incorporating your last run but it uses your recent history. So the Vo2max has a memory. This takes a while to adjust. So there is no chance that it directly goes from 45 to 41.

2. The determinants for your running performance is based on Vo2max but it's not the only driver. Running economy and performance at lactate threshold are also part of your performance. Since your Vo2max indicates a faster time, running economy and/or lactate threshold performance must be underdeveloped. Since you train pretty intense, I would say it's your running economy, if I have to make a guess.

Thanks for you reply, i updated my original post, while you replied, so i added some info at the bottom.

I believe im getting fitter on all fronts, my watch think my fitness is getting worse, because it thinks im fitter than i actually am.

Running economics - i found this description "measures runners' energy utilization when running at an aerobic intensity". The last three runs was 30 min. long. Pace was about the same, but my avg. bpm declined, resulting in Aerob TE 4.3, 4.2 and 4.1 on the last run. I would assume that when running the same distance in the same amount of time but with lower avg. hr and a lower Aerob TE score, is evidence fitness is getting better?

Maybe you need 30 days as Garmin describes

support.garmin.com/.../

Thanks for your reply. As i read it; the 30 days described by Garmin is not as long as it takes to get an accurate vo2max reading. It will create an estimate the first time you run (20 minutes or longer at 70% max heart rate.) All my runs will meet this criteria, and should update the vo2max accordingly with every run activity.

Garmin describes the run vo2max to be the most accurate and hence a vo2max estimated by a run activity will be on top of the hierarchy for 30 days - only upgraded the next 29 days only by other run activities and not by walking. If however my vo2max was first set by walking, the vo2max would still update after a run activity within 30 days because it is considered more precise.

Edit: Garmin states:

You record a Run Activity with GPS (#1 in the list) which generates a VO2 Max Estimate on May 1st. That reading will display in Garmin Connect and will only show updated readings with additional Run Activities with GPS for the next 30 days. Other activity types in the list (2 through 6) will only update the overall VO2 Max Estimate if the May 1st activity is older than 30 days because Running is at the top of the hierarchy list. 

If you own your watch 3 weeks and you train 3 times a week, than there are 9 data points for performance available. Please be patient, train additional 3 weeks an you'll see more accurate VO2max.

Maybe this post will help you: https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-5-series/217770/vo2-max-and-race-pace-disparity

And your 30 minutes runs with this aerobic impact are not helpful to close the gap between prediction and actual performance.

Thanks for reply. So i would need about double the amount of sessions than i have = 18 runs about 500 mins. total. I can appreciate that Garmin uses a more general vo2max, because your general fitness wont change a lot over the course of a run or two - i guess that's what the training effect from every run is for - where as apple watch just updates the vo2max every run, which would cause the Garmin to have a greater resolution as it splits the Aerob and Anaerob, where as the apple just combines the total fitness into vo2max. Im still a bit confused about it taking so long to adjust though. Does the Garmin couch not use this vo2max in adapting the training plans? I see there's a 5 min. benchmark run before you get a program, but there's really no way that 5 min. benchmark will be able to measure my fitness level better than the 500 min. needed by the vo2max? Sorry if im being a bit sceptical.

Thanks for your reply. I didn't get a lot of help from that thread unfortunately.

I do realize that running 5k three times a week won't massively increase my race time. I would use intervals, hill repeats, tempo runs and coordination training to achieve a faster race time. When i started running again 8 weeks ago, after 4-5 years break from running and exercising, my goal was running 5k three times a week. I wasn't able to run more than 1.3k before i was completely knackered, knee pain and shin splints almost made me quit lol, so i decided to create and follow a running program. Now im running +5k three times a week, still at a pretty hard effort but its getting better every week. Im able to run further before my HR starts to rise above HR zone 3 (at the same pace), im spending less time in HR zone 5, and if i hit +180bpm im able to recover below 175bpm by lowering my pace, something that wasn't happening 4 weeks ago - once i hit that 180bpm i never recovered i just had to bite the bullet till the end. Im even running faster pace now, at lower perceived effort and hr.

If you want a deeper look into the calculation of VO2max

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

(Firstbeat develops the training software for Garmin devices)

Thanks! I will definitely read that :-)

I was aware Garmin uses firstbeat software, but i didn't know of this more elaborate documentation.