Insights on Losing & Regaining Running Fitness3 min read

You’ve trained for weeks or months and for whatever reason, you need to take some time off from running. Whether it’s due to an injury, a trip, work, etc. there will always be a time in your life where you’re going to have to take some time off from running. You’re probably wondering, how much fitness am I going to lose by not running? While it really depends on a lot of things such as how fit you were before taking time off, how long you need to take off and other considerations, there are some general studies that have been done to answer this question.

How much fitness will I lose by not running for a week?

A well-trained runner will lose a minimal amount of fitness from not running for 7 days. Specifically, it will take about 10-days of moderate training to get back to the same level of fitness.

Personally, after taking a week off running after having finished a marathon, I did 2 easy runs and then did a more moderate run which resulted in the following paces and corresponding heart rates using my Garmin Heart Rate Monitor chest strap:

Four days later, another more moderate run resulted in:

Notice the HR is 8 bpm less for an 8:01/mile pace. This run was taken 8 days after getting back into running and it still wasn’t exactly back to where I had left off at, however you can see that my heart was getting more efficient after just a few days of moderate training and it just took a little over a week to get there.

How much fitness will I lose by not running for two weeks?

If you don’t run for two weeks, the impact to your fitness will definitely be more material. From some studies, it is estimated that you will lose between 6-10% of your overall fitness after 14-days of not running.

When you think about how much a 10% loss in fitness is, it’s basically the difference in running a 21 minute 5k vs. a 22 to 23 minute 5k which for someone who cares about racing times, that can be pretty steep.

To regain your fitness after 2 weeks, it will take more than 2 weeks to get back to where you left off. It’s estimated it would take about 3-4 weeks of training to recover from having not run for 2 weeks. You can view the fitness loss and amount of time to recover that loss fitness as something that gets exponentially bigger the more time you take off which of course can be incredibly frustrating for those who are training for a goal race.

How much fitness will I lose by not running for a month?

This one can vary a lot depending on what kind of training you do after you get back into running. From the studies I’ve read, the estimate is around 15-20% which would probably take at least 6 weeks of consistent training to get back to where you started.

In closing

If you’re really curious about how much actual fitness you lost by not running for X days, I would encourage you to buy a heart rate monitor chest strap to help you get a better feel of your heart rate at certain paces. Heart rate training is an incredibly effective way to gauge your overall fitness and to ensure you’re training at the appropriate intensities.

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