How Quickly Do You Loose Running Fitness?

Vince Sesto
Open Water Magazine
4 min readMar 1, 2022

This is something that plays on the mind of a lot of runners. You may have had a rough week at work, picked up an injury, or been off with the kids and simply had not had any time to get out for your run. But how much time off do you really need to take before you start to loose any running fitness.

With the current climate there has been times where runners have had there training effected. Even if this has not made a complete stop in training, I have noticed that even a change in intensity has then effected my endurance. But what does the research say about taking time off your racing and training.

Effects On Aerobic Fitness

Aerobic fitness refers to how your body uses oxygen to meet its energy demands during a run. If we have built up fitness over the years, when we take a break how quickly do we loose it? Most runners think they will loose a lot of fitness the minute they take a break, and this is not true, especially if you have a long history of run training behind you. If you are an experienced runner with consistent training over years, it will take a long break over months for you to see a big deterioration, so two or three weeks off for an injury or illness will not cause you any major issues.

A Link To The Study From The University Of Texas Can Be Found Here: Effects of detraining on responses to submaximal exercise — PubMed (nih.gov)

A study conducted by the University of Texas followed seven trained endurance athletes who stopped all activity for a long period of time and found there aerobic fitness, measured through there VO2Max only went down by an average of 7% after 21 days. These were trained athletes, so if you are new to running, then your fitness could be more significantly reduced with a break from running.

How Can You Slow Any Reduction In Endurance?

So knowing that our endurance should not drop off too dramatically if we do need to take a break, is there anything we can still do to slow down or prevent any decline? Firstly, strength training, is not only going to help you prevent getting injured, but it will also help if you are taking a break from run training. This could be some easy strength training or stretching, or even adding some yoga into your week. If you can cross train, spin bikes do a great job of getting your legs moving and can also provide some good strength for your running, while swimming can help with core strength and help your endurance.

If you are running less because you are struggling for time, you might want to look at increasing your running intensity, or incorporating some HIIT sessions into your week as you won’t need to be running as long but still getting a benefit from the run. Remember, a 20 minute run is better than no run at all.

How Long Will It Take To Get Endurance Back?

This is a little difficult to know as the research is a little limited and will depend on how long you have been running for. The very broad rule on getting back to your original endurance is that it will usually take twice the time you took off, to get back to where you were. For example, if you took four weeks off running due to an injury or illness, it will probably take you eight weeks to get back to where you were before your injury.

Summing Up

Don’t feel bad if you need to take a break, especially if you’re sick or injured. Even though you will loose some endurance, there is a good chance it is not as bad as you think it will be. There is a pretty good chance there is still something you can do even if you cannot run, and this should hopefully make your transition back to full training easier.

If you’re worried about taking a break after a big race, not resting can actually lead to overtraining and potentially cause further injury or illness, with some evidence suggesting that resting for up to ten days after a long race or marathon, would have very little impact on your fitness.

Check out my new book “Stop Overthinking And Start Running” for more information on how to embrace physical activity and change your life, one run at a time.

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Vince Sesto is a DevOps Engineer, Endurance Athlete, Coach and Author. One of his passion’s in life is endurance sports as both an athlete, coach and author. He is a certified running and triathlon coach with a goal to inspire people through his coaching and competition and to encourage people to live active and healthy lives.

His motto in life is, “I am trying to change the world, one run at a time”.

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Vince Sesto
Open Water Magazine

Vincent Sesto is a DevOps Engineer, Endurance Athlete, Coach and Author. One of his passion’s in life is endurance sports as both an athlete, coach and author.