What happens to our bodies when we run? Backed by science.

jogging_Whether you’re running to keep fit, training for a marathon or just looking to lose some weight, exercise changes our bodies. And we’re all aware of certain benefits to running; a healthier lifestyle, feeling good about yourself and the perfect excuse to have a treat and eat your favourite dessert.

What isn’t so clear though, is what happens behind the scenes as we run. As such, I decided to set out and do some research to identify what goes on inside our bodies as we run.

What happens when we run?

Our bodies rely on glucose for the energy required to make our muscles expand and contract as movement starts.

As we run our bodies also call on adenosine triphosphate (ATP) as a source of energy, but we keep only small stores of both ATP and glucose in our bodies, so as we run our body starts to create extra supplies.

In order to create added supplies of ATP, we need more oxygen, so we start to breathe heavier and faster. In fact, your body may need up to 15 times as much oxygen when you exercise.

A breakdown of what happens as we start running

As Laura Beil describes at Active.com, exercise puts our body through a transformation, especially in the early stages of a run:

As soon as we start:

  • As soon as we step out into the open and start our run, our body starts using ATP, the energy molecules made up from our food
  • ATP is then converted into adenosine diphosphate (ADP), another high-powered molecule to give us an energy boost

In the first 90 seconds:

  • Our cells start to break down glycogen (a form of glucose stored in our muscles) in order to produce more ATP
  • Our body only holds enough ADP to gives us a 2-3 second boost, so After the initial few seconds of exercise our muscle cells will recycle the ADP back to ATP
  • The process of converting ATP to ADP and back again causes the release of lactic acid

After around 10 minutes:

  • If we are in good shape our body efficiently uses oxygen, burns fat and glucose. At this point we feel strong
  • If we aren’t in our best shape, then it starts to get tough. Our lungs hit maximum capacity or VO2 max (the point at which the muscles surrounding our lungs can’t move any faster), ATP can’t keep up with demand, lactic acid floods our body. We start to feel sluggish and running becomes hard

All of this may go some way in showing why I personally find the first mile tough and then settle into my run after around 9-10 minutes. With the understanding that ATP and glucose are stored in the body from the foods we eat, this also highlights the importance of a good diet for runners.

Are we happier when we run?

On a side note, it’s not just our muscles, lungs and heart that are affected by running. Exercise can have a profound affect on our brain too.

I’ve long associated running with positivity and feeling good, but only last year after reading this great article by Leo Widrich did I start to understand the physical affects running has on our brains.

Research has shown that exercise can directly influence our happiness, as Leo explains in his article:

If you start exercising, your brain recognises this as a moment of stress. As your heart pressure increases, the brain thinks you are either fighting the enemy or fleeing from it. To protect yourself and your brain from stress, you release a protein called BDNF (Brain-Derived Neurotrophic Factor). This BDNF has a protective and also reparative element to your memory neurons and acts as a reset switch. That’s why we often feel so at ease and things are clear after exercising and eventually happy.

The affects of running on our body really are fascinating, especially when paired with the ability we have nowadays to track all of our food intake, calories, sleep and much more.

Have you experimented with this subject? Does running affect your happiness and mood? Do you monitor your diet before exercise? We’d love to hear your thoughts in the comments.

Image Credit: Ed Yourdon


Community Manager at Addapp. I love sports, fitness and tracking. Outside of the office can often be found on a basketball court or football pitch.

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