I recently tried 80:20 training,but after two months my VO2 max went down by a couple of points (and my zone 2 pace got much worse). But I wondered if that might not be due to the 80:20 training, but just the effect of seasonal variation (I only run out doors in the U.K.). Would a seasonal variation of a couple of points be normal between Summer and Winter?
Just to clarify - I am not talking about VO2 max measurements performed in a lab, where (AIUI) your absolute VO2 max will be measured and your relative VO2 max calculated by dividing by your (lean?) body mass. This is the gold standard, but not generally practical unless you are an elite athlete. I am talking about the estimate of VO2 max provided by a smart watch or e.g. the Cooper test. Both of these work by correlating (via e.g. a regression analysis) running performance and expected VO2 max from a population of runners that have lab based VO2 max measurements. These do not explicitly depend on bodyweight, so losing weight will not necessarily give you a higher VO2 max. If you loose fat, you will be able to run faster and your VO2 max estimate will likely go up. If you lose muscle mass, it is likely that you will be slower and your VO2 max estimate will likely go down. Those VO2 max estimates are a measure of performance, but one that is approximately calibrated with VO2 max. Whether they are a useful measure of performance is another matter (I think the Cooper test has definite advantages there as the smartwatch estimate needs to compensate for differences in effort level, which introduces additional sources of uncertainty/variation).
As suggested by @JohnP, this is my current training regime:
Monday - High intensity running, each week I choose one of:
- Cooper test & continue on to 5k (at whatever pace I can manage), followed by walking recovery, followed by 5 x 500m intervals with 500m jogged recoveries.
- 5 x 1k intervals with 1k jogged recoveries
- 10k at threshold (heart rate reserve zone 4)
- Half marathon in heart rate reserve zone 3
- Very occasionally a "race pace" 10k
Tuesday - 3k easy-ish swim (HRR zone 2 and 3, ~ 2:10/100m)
Wednesday - 15k easy run (HRR zone 2), 10k if I am feeling tired
Thursday - 20 min elliptical warm up (zone 2) followed by strength training
Friday - rest day (5k walk @ ~5.5kph - not even zone 1 most of the time)
Saturday - "race pace" 5k (most enjoyable run of the week), 5k walk, strength training
Sunday - rest day (5k walk)
So that is usually somewhere 25-40 km per week.
My training only went flat when I started 80:20 training, where I was replacing the Monday run with a 10k zone 2 jog in order to make up enough zone 2 for the "80" part.
Prior to that, my training scheme was similar except that the Wednesday run would be in zone 3 rather than zone 2 and I've only recently started doing the workout starting with the Cooper test. I'd been doing that for about a year, and it was working pretty well. The need for zone 2 running is the thing I have retained from 80:20 - I don't enjoy it, but I can accept it is good for me.
However, it could be that the flattening was just a seasonal thing, so I thought I'd check here. It is the worsening of my zone 2 pace that makes me think it may be a seasonal effect as more training in zone 2 should improve that not make it worse.
It may also be relevant that my pace often tends to improve the further I run in zone 2, see Why does my pace improve during a low heart rate (HRR zone 2) 10k?
