More than 20,000 runners from over 60 countries will take to the streets of the capital on Sunday for the 2023 Dublin Marathon.
The Dublin Marathon is now the fourth largest in Europe.
It starts at Fitzwilliam Street Upper at 8.45am on Sunday and will see participants travel through and across the capital to end up at Merrion Square North.
The Dublin Marathon 2023 routeProfessor of Clinical Exercise Physiology Niall Moyna told Lunchtime Live your body goes through a lot.
"Obviously it's hugely demanding on the body," he said.
"The two big things are when we burn calories, humans are very poor at that, we produce an enormous amount of heat.
"Heat production is one of the biggest problems that we have, and we don't want the body to overheat.
"So, then what we do is we sweat a lot to dissipate that heat, and when we sweat then we lose volume.
"When we lose a lot of fluid we could become dehydrated and that can affect our performance."
'Two fuel tanks'
Prof Moyna said the human body has two big fuel tanks - fat and carbohydrate.
"During a marathon we sort of use both tanks," he said.
"The problem is you've 100,000 calories of fat, on average, and you've only 2,000 calories of carbohydrates.
"We use roughly around 100 calories per mile; so it means at around 20 miles we run out of our carbohydrates.
"That's that famous hitting the wall because then you're relying on fat."
Hydration and food
Prof Moyna said preparations are also important.
"Ideally you want to make sure you arrive to the marathon well-hydrated and secondly make sure, every time you see a water station, you stop and take a little sip," he said.
"You don't have to overdo it but that will certainly help.
"Make sure that you take a really good meal, high carbohydrate meal, maybe a night or two before it.
"The other thing [is] that if you train for the marathon, it teaches your body to use fat rather than carbohydrates when you're actually running.
"So, hopefully you can maybe get to 23/24 miles before that tank runs dry."
Impact on your body
Prof Moyna said physical stress can also impact on the body.
"The first one is our heart; when you're pumping out this enormous amount of blood... that can cause short-term damage to your heart," he said.
"So you need to be very, very careful.
"The second one is every time your foot strikes the ground, you're going to take around 40,000 steps, and every one of them are high impact steps.
"That can cause small micro-tears and trauma to your muscle.
"Believe it or not you need to be very careful running down the hill - because it's running down the hill that actually causes the muscle trauma, not running up the hill.
"What you're doing is your muscle is lengthening while it's actually contracting, and that causes damage to the actual muscle fibres themselves," he added.
Those attending on Sunday should also remember one important detail: Summer Time ends on Sunday October 29th at 2am, meaning the clocks go back by one hour.
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