How many days can you take off before losing noticeable fitness?

I've been off for 4 months and recovery will be another 6 months. How much will I loose ? 😥

14 days

Science of Sport podcast had a spot on this topic a while back. I think they said true detraining doesn't start until after 3 weeks or so. The initial "loss of fitness" feeling folks get comes from disrupted neuromuscular connections. The good news is that once you're trained you'll gain whatever you lose back in half the time.

Yeah I agree with Guesstimate. As my own experience from doing a casual race for fun after a week off showed that my mile fitness was probably 10 seconds off my PR so the sharp race edge was off but all the fitness was still there and probably could've ran near PR just by jumping back into training for a week, whereas starting back up after my normal 2 week rest after every season I was always starting from scratch with even just slow jogging 30 minute runs feeling rough. After two weeks off it would typically take me a month of buildup to even feel like a runner again and start feeling good just doing distance runs. Somewhere from 1 week to 2 weeks I go from 95% top shape to starting back at square one.

So yeah probably somewhere around 7-10 days is where it seems fitness drops off very fast every day and within just a few days of that you're (or at least I would be) at a total fitness reset.

Based on that I'd say for someone finishing a season with no injuries or nagging pains, 7-10 days is probably ideal rest so you can jump right into solid building base rather than having to take time to regain basic running fitness all over again, but still have those few days to let the legs recover from a season. I knew someone who wouldn't take any break at the end of a season, he'd just go into base building a day or two after the final race of his season. That's a bit extreme and definitely not possible for anyone who gets injured occasionally, but it very much worked for him.

After seven days, it’s gonna take two weeks to get back to where you were.

Agreed with both. After a long season of hard racing and training, 5-7 days always felt too short to fully recover, 2 weeks turned my easy pace into threshold pace the first week back. 10 days is the sweetspot for recovery and retaining fitness.

I say it depends. Depends on your age, level of fitness, and your goals.

At 25 I could take off 5 or six days and still feel fit at workouts. But now, much older, I take off 2 days and I feel like I am back at square one.

If you are someone just looking to finish a race, then you will not feel the difference after 4 or 5 days.

..and over 50?, 60?, 70??

This is one of my favorite replies ever here, and it would’ve been even better if you hadn’t made that minor error in your math.

I just took 10 days off due to major life events (baby born, complications, chaos, everyone's healthy now). First run back (3 days ago) was a workout (6x800 @ LT, 2x400). The workout felt great, but I've been so muscle sore since that the two easy days were challenging! (Another workout today!)

about 6 hours for me and I notice the decline

Which is why I normally quadruple to stay fit

I had a different version of this a couple of months ago during the U.S. summer - had to go to South America twice for about 8 days each (1 short run the first trip, 4 short/medium runs the second), and part of the reason it took longer than expected for me to recover was that I got used to wintertime temperatures each trip and so when I returned couldn't do my normal distances even at slower paces because I was so totally unacclimated to the midsummer heat.

In reference to Jack Daniels, saying you lose fitness after 5 days...

He doesn't. There's a series of videos on Youtube and in one of them, he specifically addresses this question.
5 days off = zero loss of fitness
10 days off = a little fitness lost but comes back quickly

I was going by the text and graphs in his book (Running Formula, 3rd edition).

A personal anecdote: in 2024 I got injured leading into Boston and took 3 weeks off of running from early March to about April 1st. I was, however, cross-training on the bike for about 1-2 hours per day. I ended up PR'ing at Boston on a hot day though my quads were on the brink of shutting down for the last 12 miles - I definitely felt the lack of volume in those final 6 weeks even if aerobically I was fine because of the cross-training.

I actually find myself in a somewhat similar situation right now and wondering if anyone has experienced this. I was in great shape running 80-100 mile weeks, got semi-hurt two weeks ago and can run easy volume (70-90) but not work out. Has anyone been able to maintain their race form on easy volume like this?