My feet are pounding on the pavement, trainers rhythmically thudding against the ground with unforgiving and relentless monotony.

The breath burns in my lungs, each ragged inhalation followed by a far-too-rapid exhale.

Stinging sweat rolls into my eyes, wetting my top which bounces like a chain-mail vest across my shoulders and chest.

Every ache, niggle or pain I've felt in the last month is coming back with a vengeance.

There's still 10 kilometres to go. 

It doesn't sound like a whole heap of fun, does it?

Well, in truth, it isn't.

But in that case, why am I smiling?

Two simple words to make you run better

I, like hundreds of Australians each and every week, recently entered a running event, in my case a 30km run along the paths and trails of the Gold Coast's picturesque spit at Main Beach.

In honesty, the 30km distance was daunting to me.

Even accounting for a healthy amount of preparation, I had never run anything further than a half marathon (21.1km) before.

So, beset by pre-race nerves, I messaged my brothers, asking for tips.

For the record, my youngest brother is a depressingly fast marathon runner who recently finished his fourth London Marathon in a nausea-inducing time of two hours and 24 minutes — that's like running your local parkrun in 17 minutes and four seconds, eight-and-a-half times in a row.

Expecting a disheartening message related to pre-race stretches, nutrition plans or pace guides, what I got back was a disarmingly simple response.

It was tempting to scoff but, instead, I took those two words on board. What did I have to lose?

And incredibly, it worked.

Dr Vanessa Wergin from the School of Psychology at the University of Queensland, was not surprised.

"There is research out there that shows that running with a smiling face does help," Dr Wergin told ABC Sport.

"It helps your perceived effort of the situation and it also helps your performance.

"It's not only true for running but for many other sports as well."

Getting your gurn on

It wasn't just my brother who lives by this advice.

When former marathon world record holder and two-time defending Olympic champion Eliud Kipchoge ran the first ever — albeit unsanctioned — sub-two-hour marathon in October 2019, he did so with this quote ringing in his ears.

Good enough for Eliud, good enough for me.

But here's where I should insert a couple of caveats.

Before doing any form of event like this, it's important to train appropriately, checking in with a trusted medical professional and perhaps a coach to set a plan to get you active and healthy and into a position to achieve your goals.

Because, let's be honest, if you've never laced up a pair of trainers before, whacking a smile on your dial isn't likely to help you thunder through a sub-three-hour marathon at the first time of asking.

Equally, that doesn't mean running with a Joker-esque grin pasted on your face the entire time, or just gurning at innocent bystanders.

It means, in my case at least, that I made a concerted effort to smile to myself throughout the race, trying to remember that I actually paid to enter it and that I should enjoy being outside on a warm autumnal day on the Gold Coast — whether my hips felt like they were about to explode or not.

And, somewhat to my surprise, it made me feel better.

Perhaps it was a reaction to people on the side of the path responding, in turn, to my smile by offering an encouraging clap or cheer.

But even aside from that, every time I plastered a grin over my grimace, things felt a little easier.

And it wasn't just my imagination — there is science to back it up. 

The science behind smiling and running

In 2018, Dr Noel Brick, Dr Megan McElhinney and Dr Richard Metcalfe from the University of Ulster in Northern Ireland published a paper in the journal, Psychology of Sport and Exercise.

The aim of their experiment was to compare the effects of altering facial expressions while running and whether this had an impact on running economy or performance.