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What Happens to Your Body During a Marathon?

What happens to your body during a marathon? Quite a lot it turns out! Check out the infographic below to find out more.

Infographic showing what happens to your body during a marathon

The Burn (0-1km)

Your cells begin to break down glycogen to provide your muscles with glucose (fuel). Your muscles pull glucose directly from the blood, causing a drop in blood sugar levels. As your body uses up glucose it releases lactic acid causing your brain to alert you that you’re under physical stress.

Breathing increases from 12 litres per minute to 100 litres per minute.

Runners High (2-10km)

Endorphins are released from the pituitary gland in the brain, giving the runner pain relief and euphoric feeling known as the ‘runner’s high‘.

Shrinking (5-10km)

Water leaks from invertebrate disks in your spine, resulting in you shrinking in height by roughly 1-1.5cm.

Endocannabinoids Released (10-15km)

A naturally synthesised version of THC (the chemical found in cannabis) is pumped into the brain. This gives a sense of wellbeing and feeling of calmness, however it also temporarily impairs working memory and makes time estimation difficult.

Half Way (21km)

By this point you’ve already lost 1.5-3 litres of sweat, burnt roughly 1300 calories (in other words you’ve spent enough energy to charge an iPhone for 6 months).

Psychological Effects (25-30km)

As you deplete your glucose supply you can also experience confusion and disorientation. On top of this lactic acid build up causes cramp and soreness in the muscles.

Hitting the Wall (28-32km)

For every 1km ran, your body burns around 62 calories of glucose therefore you’ll have completely used up your body’s glucose supply by around the 32km mark. From this point your body begins to rely exclusively on fat for fuel. Because fat provides less energy per unit than glucose, you’ll have to slow down and may be in danger of ‘hitting the wall‘.

The End (42km)

Your feet have hit the ground roughly 50,000 times and you’ll have sweated out 2-5kg of water weight. Moreover, the energy you’ve burnt (around 2600 calories) is equivalent to 10 Big Macs.

Insomnia (0-24 Hours After)

High levels of cortisol (a stress hormone) in the blood can make it difficult to sleep up to 24 hours after your marathon.

Growing Taller (24 Hours After)

Over the 24 hours after your marathon you’ll regain the 1-1.5cm of height you lost in the first 10km.

Compromised Immune System (72+ Hours After)

Huge levels of stress on the body leaves you susceptible to colds and infections for several months afterwards.


Can you think of any other effects on the body and mind during a marathon? Let us know in the comments below!

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