How Long Does It Take To Lose Your Running Fitness?

How To Run Properly

One of the biggest frustrations for any runner is forced “time-out”.

There are times in your training schedule when you take time out to take a scheduled break from an intense period of training. But then there are times when you are forced to take a break because of an illness or injury.

Two weeks prior to the writing of this post, I ran the Two Oceans Marathon on the 4th of April, 2015. I ran the 56km Ultra-marathon in a time of 5 hours 24 minutes. I ran a lovely, hazard free race.

Three days after the race, I started experiencing pain in my left toe from a freak accident I had suffered at a wedding in November the previous year.

That pain, after Two Oceans, lasted over two weeks.

During this period my brain began to race through all sorts of questions and permutations. I began wondering how long my injury would take to heal.

I started calculating the amount of days and weeks until my next big race, Comrades Marathon, and wondering if I would get back to full fitness after my injury.

As an athlete, when you suffer an illness or injury, it is natural to have your brain go off on a tangent.

But why does this happen?

In my humble opinion, it happens for two reasons.

The first is that being out of action, as a person who runs for a hobby or a serious athlete, is incredibly frustrating.

The second is that you don’t want to lose the fitness that you’ve built over the many weeks or months of training.

In this post, I want to focus on the second reason because I think many people panic when injury or illness strikes. In the process, they make stupid mistakes that make matters worse.

I believe one of the best ways to stay calm through an injury or illness is by having a good understanding of how long it takes you to lose your fitness.

To address this, I ‘m going to cover the following:

  1. The two different types of fitness
  2. The “Life-long training fitness” in you
  3. Resuming your training after a lay-off
  4. The rate of fitness decline

The Two Different Types Of Fitness

Your fitness consists of Aerobic and Structural Fitness.

In essence, your Aerobic fitness refers to your ability to transport and use oxygen. This is measured by VO2 max, the maximum amount of oxygen you can use during intense exercise.

In terms of long distance running, the above definition can be reduced to one word: endurance.

Then you have what we call Structural fitness. defines it as functional fitness with medical considerations.

It goes on to say that the main things to evaluate are: medical history, posture, functional ability, range of movement through all joints, static and dynamic strength, and connective tissue health.

In essence, for you as an athlete, your structural fitness is the ability of your muscles, bones, tendons and ligaments to withstand the impact of running.

When you refer to long distance running, most people automatically assume endurance. Whilst that assumption is correct, it is a horribly incomplete one.

The “Life-long training fitness” In You

Personally, I think it’s important for you to assess how long you’ve been training as soon as you suffer an injury or illness.

When I suffered my first set-back in November 2014, I had five years of regular structural and aerobic fitness.

My structural fitness included a combination of gym-work and Kettle Bells classes. I did a lot of swimming as well. My aerobic fitness included a number of marathons, ultra-marathons and three Comrades Marathons.

In addition, from a medical history perspective, I had never suffered any major injuries.

The above is vital and I’ll highlight why later on in the article.

The Rate of Fitness Decline

Having described the two types of fitness, it is important to note that it takes longer to get structurally fit than it does for you to get fit aerobically. Equally so, your structural fitness declines much quicker than your aerobic fitness.

So how quickly does your fitness decline when your fitness and life training in you is taken into consideration?

Knowing the time-frame of your fitness decline is important. However, equally important, you need to understand the amount of fitness you lose over those respective time-frames.

1 – 13 Days

You don’t lose any fitness within the first 12 days. Any minimal losses can be re-gained quickly.

14 – 20 Days

Your initial fitness drops pretty rapidly from day 14 to 20 In this period, you lose fitness that you would have gained in the past two to three months.

The rate of aerobic loss is approximately 7%.

To regain your fitness will take a little bit of effort.

21 – 84 Days

From the 21 to 84 day-mark (12 weeks), you lose approximately 9% of your aerobic fitness.

From the 21 day mark onwards, what remains is your “life-long training fitness”. Whilst a runner with less running experience than you will lose the same amount of fitness as you in the first 21 days (supposing the two of you were equally fit), you will lose less fitness from the third week onwards because you have a higher “life-long training fitness” fitness.

Let me go back the injury I suffered on the 29th of November 2014. This was after I had run the Soweto Marathon on the 4th of November in a time of 3hrs 57mins.

I was totally inactive in December. To make matters worse, I went on holiday and the less said about my eating habits during that period, the better.

On 17th January, 48 days (7 weeks) following total inaction, I returned to training and I was incredibly unfit. On 1st March, 41 (6 weeks) days into my training, I ran a 3hours 52minutes marathon and on 20th March, I ran a 4 hours 57 minutes 50km ultra-marathon. On 4th April, I ran the Two Oceans 56km Ultra-marathon in a time of 5 hours 24 minutes.

Resuming your training after a lay-off

I mentioned above that your “life-long training fitness” assessment is vital.

When you return to training, you become prone to common running injuries because your aerobic fitness is higher than your structural fitness. As a result, your chances of running faster than the impact your body is able to handle is quite high, especially if your “life-long training fitness” is low.

Therefore, it is incredibly important to resume your training gradually, even though you feel good.

Start with shorter mileage. Run at a much slower place. Then build both your mileage and pace gradually.

If, for any reason, you are pressured by your next big race (as I am with the Comrades Marathon coming up in 6 weeks), build your mileage quickly but run it at a considerably slower pace than your usual training pace.


Suffering an injury or falling ill should not induce too much panic, unless you injury or illness is severe.

Secondly, your rest period should be driven by the date of your next major race. If your injury or illness takes place early on in your training programme, I highly recommend you take enough of a break and make sure that you heal completely.

Too many runners are under the impression that allowing full recovery will result in a complete loss of fitness. As a result of this, they often don’t wait for complete healing. They heal partially and are back at full training, often aggravating the situation and making it worse than it originally was. This is the reason why many runners have re-occurring injuries.

When you get injured and get ill, relax and take a chill pill. You’ve worked hard to get fit.

Your body and brains are much smarter than you think. Start giving them more credit.

I hope you have found value in the post. If you have, I would highly appreciate it if you shared it.

God Bless!

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