What happens to your body during a marathon?

We get asked all the time what to wear for a marathon. While there’s no one-size-fits-all answer, in general, our advice is to invest in comfort. Buy the best base layers you can afford, and find budget for a pair of really good running shoes. Both make you more comfortable, which will help elevate your marathon pace. But what happens to your body during a marathon, and can what you wear really make any difference? 

Hundreds of pairs of feet pound the streets during the Freiburg marathon


The intense level of exercise required for long-distance running can drive your body temperature up significantly: your body produces 30 to 40 times the amount of heat during a marathon. The body’s reaction is simple: sweat glands produce moisture, which then provides you with a cooling sensation as it evaporates. To help keep cool, drink plenty of water and think about investing in some sportswear with good moisture-wicking properties. At AG Sports, we stock some of the best base layers in the world. Carbon Energized garments are designed to keep your body temperature up to three times lower than polyester base layers. And even better, they are so lightweight, you’ll hardly know you’re wearing them.


Did you know that marathon runners lose up to six litres of sweat over the course of the race? Dehydration can easily occur under these circumstances, so it is important to drink plenty of water. If race day arrives and it is warmer or more humid than expected, think about additional ways of keeping cool, such as adjusting your planned attire. When you plan what to wear for a marathon, try and account for all weather conditions. You don’t want your marathon pace to be thrown off by dehydrating.

40,000 steps

It takes about 40,000 steps to run the 26.2 miles in a marathon. Every step impacts on your joints, making you feel sore, especially in your calves and thighs. Couple this with lactic acid build-up and you can start to feel the burn intensely, affecting your performance and marathon pace. It’s worth knowing that the technology now exists for some garments to reduce lactic acid levels, helping you to feel more comfortable. And if you’re unsure where to prioritize your budget for what to wear during a marathon, we’d always recommend a great pair of running shoes, to help mitigate the impact of 40,000 steps.


Your body responds to the pressures of a marathon by producing adrenaline, which elevates your heart rate and increases your breathing. Adrenaline is a powerful hormone and can help you to feel like you’re keeping to your marathon pace in the early stages of the race. But it can push your heart rate and breathing up, and so you need to stay cool, practice your breathing techniques, and keep hydrated. Our products can help too: Carbon Energized garments can reduce your heart rate by up to four beats per minute and improve your lung function. It’s one of the many reasons they’re considered some of the best base layers in the world.

Blood sugar levels

Your body will burn more than 2,600 calories during a marathon - more than humans can actually store. This means that towards the end of the race, your body will resort to burning fat instead of glucose, which is a much less efficient fuel. Low blood sugar levels at this point lead to many runners slowing down, hitting ‘the wall’, or worse still, developing hypoglycaemia. Prepare ahead by stocking up on sports drinks or sugary gels to give your glucose levels a boost when you feel your marathon pace is flagging.


No matter what you go through during your marathon experience, it’s one of the biggest accomplishments you can achieve. What are your top tips for what to wear for a marathon? What has helped keep your marathon pace on track? We’d love to hear from you!