If you stopped training, how many weeks would it be until you could no longer run a sub-20 5km?

Most people don't realize how much fitter you get after just a little bit of training. That's also a reason why physiological experiments on untrained subjects aren't worth the paper they're written on.

except when they are. 99% of America is untrained and these papers are relevant to that large group

Some relevant info on loss of fitness according to Jack Daniels:

"First, however, we ought to consider the alternative to “cross training” during time off due to injury—complete rest. Dr. Jack Daniels, one of the pioneers of the use of threshold training, quantified the drop in fitness that occurs due to time away from running in his best-selling book, Daniels’ Running Formula.

Daniels’ work exposes a few important points: first, there is virtually no drop in fitness as a result of missing up to five days of running. After that, your conditioning drops more sharply, then “bottoms off” after about ten weeks (representing your “baseline” fitness as a sedentary individual).

After about a week or two away from running, the differences between those who cross-train (by any means) and those who take complete rest begin to emerge. Though the gap is only about two percent after fourteen days, this increases to ten percent (80% of initial fitness vs. 90% of initial fitness) after ten weeks or more. This means that a [4:30]miler who takes 10 weeks completely off will (in theory) regress to [5:32] without cross-training, but only [4:57] with it."

https://runnersconnect.net/running-injury-prevention/losing-running-fitness/

You guys are way overestimating your ability to hold on to your fitness. I ran sub-16 in HS and 5-6 years later couldn't break 22 and hadn't gained significant weight.

Does that include eating dirty again? If so, not long.

HobbyJoggerToRunner wrote:

People are way over estimating their abilities here.

At the age of 27 my 5k PR had dropped down to 18:10, and mile PR 5:02

I had a bad injury and by the time I came back to running at age 30, in a 5k time trial I ran over 24 minutes (not a fluke). I don't think you guys realize what several years of no running (with no other aerobic sports) means for your body. You go down hill very quickly.

You did, I didn't.

well over 40 wrote:

HobbyJoggerToRunner wrote:

You go down hill very quickly.

You did, I didn\'t.

This pretty much sums it up. It\'s highly individual.

As a natural 400-800 guy I don\'t think I lose my top end speed easily, but my 5k time drops very quickly. I guess people with a natural ability for the 5k (high VO2max amongst other) would not lose as much as a sprinter or a marathoner.

At 40 I was in 17 minute 5k shape. Had an accident and didn't run for 2.5 years. I did train on the Stairmaster. I ran 7 minute pace for 5k.

Last year at 50, I ran 18:40 but right now I would be lucky to run much faster than 20 minutes. My answer would be 3 weeks.

it's hard to come back wrote:

zephito wrote:

Did a test mile on treadmill 4 weeks ago after one week of 2 mile jogs, ran 7:14 and almost had a heart attack.

Without those 2 mile jogs I guess your test mile would have been at least half a minute slower. Most people don't realize how much fitter you get after just a little bit of training. That's also a reason why physiological experiments on untrained subjects aren't worth the paper they're written on.

You could be right. A good portion of the improvement comes right off the bat. However, it was right after a hard lifting workout, I didn't warm up much and I went out too fast - 6:45 pace for first quarter ("I'll just start slow then speed up!!!"). Regardless, I couldn't run a 6:45 mile, so that's pretty bad. I figured I could still run a mile in at least the low 6s. Uh uh.

I've gotten my runs down (I think) to about 7:45 pace for 5 miles without undo difficulty. Eventually hope to work it down to low 7s.

I have a friend who was a 15:30 guy at age 20 who's just coming back after 15 years of not running. He figured he was still in at least 18:30 shape. His first run he told me he went 3 miles and was sprinting in full blast and still couldn't get the last mile under 8. You can lose a lot.

I ran 19:31 zero training when I was 13 with no idea how to race or anything. I think I could go sub 20 without training until I'm around 55 years old, and if I stopped training for a year or two right now I would be around 18 flat.

I might add that people who retain well often seem to lack high trainability.

I also hang onto whatever trained fitness I get longer than normal.

well over 40 wrote:

I might add that people who retain well often seem to lack high trainability.

I also hang onto whatever trained fitness I get longer than normal.

Exactly. With a year of doing absolutely nothing, I run ~18:30. With a year of hardcore training, I run ~17:30. Extremely meh. I'm about as untrainable as you get. I'm 28 years old today btw. Happy bday me!

15:30s pr 10 years ago.

Have run intermittently but nothing serious.

I have probably averaged 150 miles per year since my pr.

I'm 32 now and could drop a sub 20 today if needed.

I agree that this is highly individual, though. I have a "big engine" but not much speed. Natural endurance but not a high ceiling. 15:30 was about as fast as I was going to get. Maybe could have broken 15 with another 2 years of serious training.

I'll bite. I quit running when I was 23. I had just run mid-24 for 5 mile on the roads.

For three years, I drank at least a 12 pack/day and a 30 pack every Sat/Sun. I smoked two plus packs a day, ate like crap, and worked construction. Sometimes I'd run a brick saw a full eight hours with no mask, go home and blow a brick out of my nose.

Three years later, I decided to start running again. The first day I ran three miles in 22:00 (March 1). By June, I ran 5k in 15:52. My guess is I could have done it on day one, so I would say at least 36 months.

As an aside, my twin brother who has always been a smoker came out the first day of senior year H.S. and ran 19:30 for three on a training run.

I was a low 31 10k guy in college, but I was constantly hurt. It finally got so bad I had to quit the team and have never really recovered.

However, every now and then I try to get out there again. I remember once, after about three years off, a friend wanted to run an all-out mile on the track. I decided I would just try a hard 5k. I ran about 18:30 solo and it was hard, but totally doable. I hadn't run a step in years.

Several years later, my fiancee (now wife) wanted to do a 5k road race. I signed up and ran ALL OUT in 20:08. It was a 4th of July race and I remember a chubby guy dressed in an American flag, high-fiving all the spectators, whom I couldn't beat. That was sort of a wakeup call. I tried to start running again, but always got injured within a couple weeks.

Now, I'm 33. I'm trying to sort of run again, but it's awful. I run 8 min pace in training and it feels hard. I don't believe I could break 6 for a single mile, even with wolves chasing me.

Never

.

Keep trying to sort of run again.

I was in a similar situation as you in my early 30's. I felt like a complete loser training slower than 8:00 pace when I used to train around 6:20. I got discouraged and gave up.

Starting coaching my kids middle school team last year, working with those kids lit the fire in my belly to start running again. Unfortunately now I'm ten years older, 20 pounds heavier and that 8:00 pace that I hated has turned into 8:40. I'm commtted now, but I kick myself everyday because I didn't push through the tough times 10 years ago

My dad ran a 20 min 5k at age 46, I'm 25 and if I maintain my current bmi/bf % i could probably run a 20min 5k till at least 45 (hopefully) with an active lifestyle; hiking, walking, lifting, basketball etc.

I know exactly what it's like, though I was never anywhere near 31 min for 10K. I did my treadmill test after a 5 year layoff, expecting around 6:30 for the end. I started at 6:45 pace. After about 200 meters there was the awful realization that this was too fast and that I was going to suffer through the next 1400 meters. It was amazing. I could tell I wasn't moving my legs that fast, but I was trying to grab all the air in the room and my heart was banging away at what felt like 200 bpm. I had to slow it down throughout the run, then push Emergency Stop after I hit 7:14. That was a big wakeup call.

It comes back pretty fast, though. That was about a month ago and I'm comfortably running 6 miles in well under 48 minutes. The last 10 days I've noticed a definite pickup in speed.

arun1 wrote:

You guys are way overestimating your ability to hold on to your fitness. I ran sub-16 in HS and 5-6 years later couldn't break 22 and hadn't gained significant weight.

I was a 14 min guy in college. Trained for 2004 marathon OT but came no where close (2:25). Got married. Had kids.

I hadn't trained in 13 years, I'm 39 now. I ran a 19:13 5k a couple months ago with a friend.

i felt like crap being 5+ min off my PR. Let's not pretend this is some holy grail.