You’ve been hit by Covid, or maybe a running injury, and are wondering how long it will take to lose that fitness you’ve built?
How long does it take to lose aerobic fitness?
First, I’ll start by quickly explaining what aerobic fitness is. Aerobic exercise is basically any form of exercise that requires oxygen. Any running over 400 meters is included. As we train more we build up our aerobic fitness. This enables us to train longer at higher intensities.

How long does it take to build aerobic fitness?
Most studies show that cardiovascular training requires a minimum of 30 minutes, 3 times a week to guarantee increased aerobic capacity in about 8 to 12 weeks (https://www.ucdenver.edu/docs/librariesprovider65/clinical-services/sports-medicine/training-for-cardiovascular-fitness.pdf ). So that’s 2-3 months of regular runs will build a good level of aerobic fitness.
How long does it take to lose aerobic fitness?
If you’ve been running a while then it will take from 7-14 days for you to start losing fitness. And this will only be the fitness that you’ve built in the last month. So if you’ve got injured, or you have Covid (like me) then don’t worry! You won’t lose fitness that quickly. From my experience it is in your best interest for your health and long term running to take a break!
The importance of taking a break from running
Training hard at running can put immense pressure on the body. It has been shown that actually taking regular breaks to let your body recover can actually make you a better runner. If you have been struggling to find those gains recently then maybe you just need to take a break. I have seen a massive improvement in both mind and body from scaling the running back and starting to implement more relaxing exercises into my weekly routine such as yoga. Yoga has soothed my aches and pains and has started to develop some much-needed core strength. You are probably reading this because you are ill or injured and frustrated that you can’t run. But please do not worry, you won’t lose that much fitness after a bit of time off running.
