This Is What Running A Marathon Does To Your Body

We hit the ground running -- figuratively speaking, of course -- with these experts to find out what running 42 or so kms does to someones body.

"In the months or years leading up to a marathon many changes occur -- some are positive and some negative,” Drew Harrisberg, an exercise physiologist, told 10 daily.

Physically, marathon runners experience muscle atrophy -- which is a technical term for losing muscle mass.

While this is beneficial for running (and running, and running …), the pay-off is a loss of strength.

Compare a long-distance runner’s body to that of a sprinter -- they’re both runners, Harrisberg explained, but the former is lean and light while the latter is muscly and heavier. Their bodies are honed for a specific purpose.

The muscles that marathon runners do have see an increase in something called mitochondrial biogenesis -- that basically means their muscles cells are firing on all cylinders to keep them going.

Their bones might become denser too due to the sheer force of pounding that pavement.

Here's another science-y term coming at you -- increased aerobic threshold.

Marathon runner'’ aerobic threshold lifts its game in a big way to help the body use up slow-burning fuel sources at a cool, calm and consistent rate.

"This means you don’t hit the wall," Harrisberg said.

READ MORE: Expert Tips To Stop Hating Running And Actually Start Enjoying It

On the flip side stress hormones like cortisol also kick off because well… running over 40 kms tends to stress the body out.

Skip past if you’re squeamish -- Harrisberg told 10 daily that some people get blisters, chafing and their toenails fall off. Yuck.

Long-distance runner and Jaybird ambassador Andrew Papadopoulos says that he’s even finished a run shorter than when he started.

Say what?

"I've lost a few centimetres in height … due to temporally losing fluid between the intervertebral discs," he said.

And that’s not all you can look forward to.

"I think the most bizarre by-product is waking up the next day and finding it hurts to breathe.

Nothing is wrong with your respiratory system however all the muscles that support your breathing have worked to their extreme and you certainly feel it," he said.

On the run

Muscle wastage? Missing toenails? Getting shorter? Sounds like maybe running just isn’t for us humans -- it’s more a cheetah thing right?

Not according to Harrisberg -- "Are we built for running long distances? Absolutely!" he said.

Humans literally evolved running -- we are bipedal hominids. During our hunter-gatherer days, we would catch our prey by out-running them to the point of exhaustion, and there are tribes in Africa who still catch food this way.

It’s also no surprise that African marathon runners are the best in the world.

Before we all lace up our Nikes and hit the road, there is a 'but.'

"Just because we can run long distances doesn't mean we should be running every day,” Harrisberg said.

"Sure, some running has been shown to improve lifespan, health span and overall wellness, but just because 'some' is good doesn’t mean 'more' is better," he explained.

Running out of steam

So how much is too much?

"A few marathons a year is perfectly fine," Harrisberg told 10 daily, "but we are not designed to run the number of hours and kilometres that addicted marathon runners complete every single day of their lives. We just aren’t."

Even running for two hours every day and not recovering properly is a recipe for disaster in his opinion.

In extreme cases, Harrisberg told 10 daily that pushing the heart to its limit can result in ‘cardiac adaptations’ such atrial fibrillation and atrial flutter -- an abnormal heartbeat -- and ventricular hypertrophy which is a thickening of the heart’s wall.

On top of muscle and bone wear-and-tear your stress hormones can remain high, even after you finish running, and your adrenal system can become seriously worn out which can mean tiredness, mood swings and anxiety.

This is where proper, safe training comes in. Papadopoulos told 10 daily that his pre-race prep has meant that he's avoided injury and long-term issues.

"The key is to begin training well before the event so you don’t overexpose yourself to high volumes of running in a short period which can lead to injury or niggles," he said.

READ MORE: If A Woman In A Run Club Falls In The Forest, Does Anybody Hear?

As unbelievable as it sounds some marathon newbies rock up to their first race having done no training at all -- according to Papadopoulos "they soon realise how harsh the reality is of this difficult sport."

Harrisberg told 10 daily that a coach is key -- they can help ease first-timers into long distances by tackling shorter distances first. This is called ‘interval training’.

"It’s very effective," he said.

Crossing the finish line

So, do the benefits of running marathons outweigh the risks?

It’s a “touchy topic”, said Harrisberg.

If you can strike a balance between running and recovery, "I think it definitely does more good than bad," he said.

Feature image: Getty.