How much fitness do you lose in November?
Less than you think.
The season is over, the race is done, and one question keeps nagging: if I ease off now, how much of all this will be left by spring? The answer is specific, measured long ago, and far calmer than the fear of the sofa suggests. But it comes with one catch — and that catch decides whether November is a break or a loss.
The recovery phase after ŁUT forgot one thing
After ŁUT 150 my plan moved into its recovery phase. In the second week it scheduled what I expected: easy runs, mobility and rest days. I did strength anyway — core and functional work, on my own initiative. But the report couldn’t credit it: it set 25 minutes of strength against 40 planned minutes of mobility and treated it as unfinished mobility.
I checked where it came from. It turned out the block generator didn’t schedule strength at all in the recovery phase — not by anyone’s decision, just an oversight. Strength lived in the code only in the base-building phase. I knew not to drop strength after a race, but the plan didn’t — and a user who trusts the plan would have dropped it. I fixed it: since 25 October the post-race block prescribes strength from week one, and the report no longer compares gym minutes with stretching minutes.
This piece is about why that matters. Because the off-season is not a question of whether to rest. It is a question of what to keep while you rest.
Three different things under one word
When people say “off-season”, they mix up three things with different goals and different clocks:
1 · Recovery
days after the race
repair: muscle, blood, sleep
goal: add nothing
2 · Transition
weeks
less, but not zero
goal: keep what is costly
3 · Rebuild
start of the next block
base first, then stimulus
goal: start from a higher floor
this piece is mostly about the middle box
What happens when you stop completely
The most cited data come from a study in which seven trained endurance athletes simply stopped training while researchers measured them for 12 weeks. Maximal oxygen uptake (VO2max) fell 7% in the first 21 days, and after 56 days it levelled off 16% below the trained value — and stopped falling. ↗ study
Three things are worth remembering from this chart. First: the drop is fastest at the start, then slows. Second: it has a floor. After 84 days without training those athletes still had a higher VO2max than people who had never trained — 50.8 versus 43.3 ml/kg/min. Third, and most important: you don’t have to ride this curve at all.
What goes first, and what stays
The same study showed that fitness doesn’t vanish in one piece. It breaks into parts with very different lifespans:
Heart: stroke volume
drives the early drop in VO2max
Muscle: aerobic enzymes
half the drop in about 12 days, then settle above untrained levels
Muscle: capillaries
after 12 weeks still 50% denser than in untrained people
That is good news for ultrarunners. The things you build over years — a denser capillary network in your muscles, their ability to burn fat and work aerobically — are the most durable. What goes fastest is what comes back fastest: blood volume and how much the heart pumps per beat. Two weeks off is enough to measure it — in 15 runners VO2max, stroke volume and thigh strength fell, but muscular endurance stayed. ↗ study
After an ultra, rest is not laziness
Before you start fearing fitness loss, an honest note: after a long mountain race the body has more to repair than the soreness suggests.
Thigh strength was down 41% at the finish while grip barely changed — local fatigue, in the muscles that braked on the descents for 156 km. ↗ study Another study this year, on UTMB runners (171 km), showed something you can’t feel in your legs: red blood cells lose their flexibility, and the body starts clearing out the damaged ones. ↗ study The authors did not assess long-term effects, but the takeaway for November is simple: the first days after an ultra are repair, not training.
I wrote separately about why descents wreck your legs while your watch only sees your heart, in the piece on downhill running.
How much training is enough to not lose it
Here is the catch from the start. A review of research on the minimal training dose says it plainly: you can cut volume hard, but not intensity. ↗ study
| What to keep | Minimal dose in the research | How long it works |
|---|---|---|
| Endurance | 2 sessions a week, or 33–66% less volume — with effort heart rate kept | up to 15 weeks |
| Strength and muscle | 1 strength session a week, 1 set per exercise — with load kept | up to 32 weeks |
One caveat that matters for most ultrarunners: the strength dose comes from studies on younger adults. In a randomised trial, people aged 60–75 needed a larger dose to keep their muscle gains than people aged 20–35. ↗ study The older you are, the less you can afford to cut strength.
The off-season is not about stopping. It is about training less — without losing what was most expensive to build.
How UltraFlow handles it — and what it can’t do yet
After a race the plan moves into a recovery phase: less and easier, and the report is allowed to say “not yet” when you come back too fast. Since 25 October that phase also prescribes strength from week one — for the reason I described at the top. The general principles behind it are on the research page.
Honest about the limit: today I compute the post-race recovery window from distance and climbing, but I don’t yet tell 1,000 metres of descent from 1,000 metres of ascent. And the 156 km finish data show it is precisely the descents that wreck your legs. I’m working on it — until then, if your race had a lot of steep downhill, add a few easy days beyond what the plan shows.
Three things for November
1. Repair first. The first days after an ultra are sleep, food and walking. No “running off the soreness” — your legs lost over a third of their strength at the finish and need time, not stimulus.
2. Cut volume, not intensity. Research says two sessions a week are enough, as long as intensity stays — a few brisk segments, not just jogging. The long runs can wait for the rebuild.
3. Don’t shelve strength. One session a week holds it for months; for older runners, two is safer. It is the cheapest investment in spring — and the one your watch will miss, because it doesn’t show up in heart rate.
Plan your off-season on your own data — 14 days free
A plan that moves into recovery on its own after a race, prescribes strength from week one, and tells you each morning whether you can add more yet. 14 days free, card at signup, cancel any time.
Sources
Coyle et al., loss of adaptations after stopping training, J Appl Physiol 1984 — DOI · Spiering, Mujika et al., minimal dose to maintain endurance and strength, J Strength Cond Res 2021 — DOI · Bickel et al., maintenance dosing in young and older adults, Med Sci Sports Exerc 2011 — DOI · Chen et al., two weeks of detraining in runners, Eur J Sport Sci 2022 — DOI · Markov et al., strength and power across a 156 km ultra-trail, Front Sports Act Living 2026 — DOI · Nemkov et al., red blood cells after UTMB, Blood Red Cells & Iron 2026 — DOI