Athletics Magazine

How Fast Do Runners Lose Fitness?

By Brisdon @shutuprun

As I sat around all week unable to run I could feel my fitness slipping away like the grains of sand through an hour glass.


I love being dramatic.

I do know that this cock-six injury will not last nearly as long as other injuries I’ve had (#1, #2, #3), but still – not being able to run makes me cranky, bitchy and generally just not as nice of a person.

I am holding on so tight to my fitness level and do not want to lose one stinking bit. I know that is irrational – I mean it’s only been 5 days sans running – but these are the things I think about. I had high hopes for the LA Marathon and my training had been going so well….wah, wah, wah. The good news is that I was able to do a short run today with some pain, but not too bad. My PT said that running if my pain is about a level “5” should not give me any problems or keep me from healing. The worst is still just sitting, sneezing and getting out of the car.

I decided to research just how quickly we runners lose our fitness if we sit on our asses. And, really, that is what I have been doing because cycling hurts and yoga hurts and I just didn’t feel like swimming and I hate the elliptical (there I said it).

Here is the reality regarding fitness loss:

  • Fact #1 –The biggest change in the body when one takes time off is in how the body consumes and process oxygen (VO2 Max)

1 week off = negligible decline
12 days –> 3 weeks off = 7% decline
3 weeks –> 12 weeks = 9% decline

  • Fact #2 (good news!)– If you’ve been training for a long time and have relatively high endurance, you can maintain your fitness longer than someone who has more recently started exercising.
  • Fact #3 (crappy news!) – It takes at least twice as long to gain fitness as it does to lose fitness.  That means if you detrain for 12 days, it could take you up to 36 days of retraining to get back to your original fitness level
  • Fact #4 (good news!): Cross training and shorter/high intensity workouts can reduce the amount of fitness lost. Even doing lower volume, higher intensity workouts 2 to 3 times per week can help maintain fitness.
  • Fact #5 (important news!): Even if you are not injured, it’s good to take time off from running every now and again, or significantly cut back just to give your body a break.

Moral of the story: It is important not to panic. Even if you are injured and need to stop running for many weeks, this doesn’t mean you will lose all fitness. Naturally, you will have to work your ass off to get back to your pre-injury fitness level, but see this is a challenge and a goal, not a reason to be completely devastated and destined to a life of self pity and cookie/cake bingeing.

If you are an IR (Injured Runner) and are in a really dark place – read “10 Ways to Survive Your Injury Without Being a Bitch” and “The Stages of Injury Grief,” written by yours truly.

For more info about losing fitness (and the source of the above info) check out these articles:

How Long Does It Take To Get Out Of Shape? – Competitor
Use It or Lose It - How fast do I lose fitness if I stop exercising?Sports Medicine
How Long Before You Lose Your Fitness Level? – Runner Academy


When was your last running injury that you had to take a lot of time off for?  I really haven’t taken time off due to a running injury since my hip stress fracture in 2010.

What cross training have you done during an injury? I’ve done tons of water running, cycling and swimming.


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