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How Fast Do You Lose Cardio Fitness Level

You Asked: How Quickly Will I Lose My Fitness Level?

Dear Fit,
I've recently become a running addict and train with a group of people who have an incredibly high fitness level. However, for two weeks within the last month, I wasn't able to exercise and now I'm afraid that I've lost all of the fitness I've built up. I am planning to start back exercising today, so I'm not worried about never becoming fit again, but it has made me curious about how quickly someone can lose their fitness. I've heard it takes only seven days, but I don't know how true this is. Can you help me figure this out?
Running Out of Time

This is a great question and something a little out of my range of expertise. I consulted with IDEA Health & Fitness Association Expert Fitness Physiologist Jason Karp Ph. D. to research the subject. To hear what I learned,


It looks like you under estimated the amount of time it takes to lose cardio fitness less, but just by a bit. According to Dr. Karp "within one to two weeks of stopping exercise, changes can already be seen in cardiovascular fitness." There are decreases in mitochondrial density (the mitochondria is considered the body's aerobic engine on a cellular level) and VO2max, aka maximum oxygen level consumption. Karp also added that "decreases in strength don't happen as quickly as decreases in cardiovascular endurance." I guess muscles do have more memory than the heart and lungs.

"Unfortunately," continued Karp, "It takes longer to gain fitness than it does to lose fitness. How much longer depends on a number of characteristics (age, level of fitness before taking a break, genetic responsiveness to training, etc.)." If you cannot work out at the frequency you're used to, all is not lost. If you need to decrease your workouts from five days a week to three, Karp suggested making one or two of those three days high intensity workouts.

Good luck getting back into your training and keep us posted on how the marathon goes.

Image Source: Thinkstock
guavajelly guavajelly 7 years
I stopped working out for about a year and it was a huge mistake. I gained weight, became a bit down, and frustrated. But, since May I've jumped back on working out, though i'm not even a fraction of what I use to be :( The workout high is definitely back, so hopefully my fitness level will be too!
cotedazur cotedazur 7 years
When I was in high school and doing three sports competitively, ALL of my coaches recommended taking off a week between seasons. Three times a year, I took a week where I did no athletic activity whatsoever. I feel 100% confident that these three weeks had NO negative effect on my cardio fitness level; if anything, I came back feeling more energized and re-focused. Now, whenever I go on vacation or can't get in a workout for a week, I tell myself it's my "week between seasons" and let it go. I think it's best not to stress too much about working out every day.
inlove23 inlove23 7 years
This always stresses me out! I'm afraid that if I don't run for 3-4 days I lose everything I've built up (I'm a fairly new runner). But, the majority of the time I'm just fine, if not better.
PhoenixRising PhoenixRising 7 years
I agree with Chloe and Darc. Last summer I started the Couch to 5k program, and, for various reasons, I did not keep up with it. Months passed between the times I fell off and the times I decided to restart. I was shocked at how much my cardiovascular fitness had maintained itself throughout. I was able to pick where I left off despite the long break. I did take up hula hooping in the mean time, but I don't think that alone would make up for the lack of running. I think the benefits of exercise last longer than many people would credit.
Spectra Spectra 7 years
I've never taken more than a few days off of working out in a row, so I don't know how my body would respond to it. I did have a two week period where I couldn't work out for very long, so I did 10-15 minute intervals where I'd run up and down stairs or jump rope just to get my heart rate up and get myself moving. Once I returned to my old routine, I was able to jump back in fairly quickly.
Soniabonya Soniabonya 7 years
I think I lose my fitness level very quickly. It was very apparent when I was in water polo and swim team. Take a day or two off for injury or illness and hitting the pool after is like chaining weight to my body. I hate the feeling.
darc5204 darc5204 7 years
I agree that it's a terribly misleading answer. Maybe in one or two weeks you can see the first signs of lessening fitness, but that's not at all the same as losing all of your progress. It takes a long time to lose muscle too, unless you're bedridden or starving.
GlowingMoon GlowingMoon 7 years
I don't know about losing fitness, but I do think there is such a thing as muscle memory. Your body will get back in shape fairly quickly. Personally, I've taken breaks from certain exercises. When I returned to that exercise (after a long hiatus, like months later), I was able to perform at my peak within a few sessions. My muscles remembered.
Splintera Splintera 7 years
I've always wondered about this so I'm glad you touched upon this question. Damn, seems like you do have to keep a very regular workout routine if you wanna keep your fitness.
chloe-bella chloe-bella 7 years
You will not lose "all the fitness" you've built up just by taking 2 weeks off. I find this answer to be a bit misleading. Yes, you will "lose fitness" in the sense that your fitness level will decrease; but if you've been running for some time, you will not, by any means, go back to square one in a mere 2 weeks. I've had to take between 1 week to over a month off from running several times in the past 3 years due to various injuries, and while my fitness for sure decreased, I could still run at least 5 miles at my normal pace comfortably when starting back up again. The only time I've ever "lost my fitness" completely was when I went an entire year without working out at all. Chances are, the distance/pace that felt easy to you before you took the two weeks off will feel slightly hard toward the end when you start back up, but it's not like you suddenly won't be able to run at all.
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