How quickly do you lose running fitness?

Author: Women's Running Magazine

Read Time:   |  November 17, 2017

Group of women runners walking in a forest, close up

When a planned rest day turns into a rest week, a nagging injury keeps you from running or you’re off on holiday, you can expect to feel a bit guilty over a dropped exercise habit. Then there’s the fear of how much fitness you will lose.

“If you’re only taking a few days off, it allows your body to recover, replenish glycogen stores, adapt to the training and get stronger, not to mention refresh you mentally so that you’re keen to run again,” explains exercise physiologist, John Feeney ( “Take longer and it will affect your fitness, but the good news is it’s all reversible.”

Blood pressure

In the short term, your blood pressure is affected immediately, because running increases blood flow to the heart and this, in turn, prompts your arteries to widen to enable greater circulation. The arteries remain like this for up to 24 hours before returning to normal if you don’t exercise. But these effects are only temporary and it’s only after 12 weeks that your arteries can begin to narrow and harden if you remain inactive.

What to do: Even if you can’t run, other forms of aerobic exercise, such as walking for 60 minutes, will help to keep your blood pressure low. Studies have shown women who walked briskly for at least three hours a week had the same protection against heart disease as women who ran for 90 minutes a week.


As women, it’s difficult to create dramatic changes in muscle by running alone, because we have lower levels of testosterone, which helps men to build muscles. But it does improve tone, strength and elasticity in the muscle fibres, particularly with added hill training and pace work. So, does that mean when we stop running all our muscles will turn to fat?

“No, because muscle tissue is different from fat, so you can’t change one thing into another,” explains women’s running coach Tara Shanahan ( But if you take time off for over six weeks, you will start to lose muscular endurance, strength and tone.

What to do: How quickly you regain muscle strength and endurance depends on how often you train, but the best news for those who end up having to take a lot of time out? You will see bigger improvements more quickly than someone who was fitter.

Body Fat

When we run, our muscles process insulin and absorb the resulting glucose, which is released to power our movement as we run. Stop running and your muscles quickly become less sensitive to insulin, according to research published in the Journal of Applied Physiology. As well as increasing the risk of Type-2 diabetes, this also means calories from food are no longer converted to energy for the muscles and are instead stored as fat.

What to do: Don’t fear, it’s not as dire as it sounds. Studies show your body can adapt quickly to increased insulin with other forms of exercise and healthier eating. High-volume exercise, such as an hour-long walk or high-intensity exercise of just ten minutes a few times per week is just as effective at ensuring your body continues to process insulin.

How quickly lose fitness 2

The body will adapt quickly to increased insulin with other forms of exercise

Aerobic fitness

Remember how out of breath you felt when you first started running? While research shows you won’t be starting from scratch after taking time out, your VO2 max or aerobic capacity is affected within two weeks.  “This is primarily due to a reduction in the heart’s efficiency and the number of capillaries in the muscles, which affects their ability to absorb and utilise oxygen to help you run,” explains Feeney.

What to do: If you were already super fit before you took time out, regaining aerobic fitness won’t be as hard. For anyone else, it will feel harder, which could be more discouraging. The best thing to do is start back from scratch, even if this means returning to a walk-run training plan until you rebuild your aerobic fitness. This way you won’t tax your body too much and be left feeling discouraged. If you’re out due to injury, try sport-specific training like aqua running to prevent reductions in aerobic capacity.

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Aqua jogging is a great way to maintain aerobic capacity

Mental health

Ever finished a run and found yourself in a bad mood? Unlikely. This is because exercise releases the feel-good hormone serotonin and, the more frequently we run, the more we get used to running as a mood booster. Stop and you can expect to hit the wall pretty quickly.

Not only that, but studies suggest that our ability to handle the anxiety of training and races may also be affected. When we feel challenged, such as at the beginning of a race, our fight or flight response is triggered, causing a rush of adrenaline. The more we run, the better we become at handling this anxiety and harnessing the positive effects.

What to do: “Think of your mind as a muscle that can be trained just like leg strength,” explains Katherine O’Hara, a holistic performance coach ( “Coming back from time out and regaining your focus is just a question of training. Ultimately, your mind can talk you into feeling more relaxed. If you tell yourself you’re anxious, you will be. But if you tell yourself it’s a great opportunity, you’ll be excited and are more likely to feel in control.”

Women's Running Magazine

NMA’s 2020 Lifestyle Magazine of the Year, Women’s Running provides expert advice on gear and training, motivation from your favourite runners and the latest running news.

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