What Happens to Your Body During a Marathon? | Unveiled

VOICE OVER: Noah Baum WRITTEN BY: Caitlin Johnson
The marathon is one of the most popular tests of human endurance. Globally, there are over 800 marathons held every year, for professional athletes and amateur runners alike. But exactly what are you willingly putting yourself through when you sign up to a race? In this video, Unveiled discovers exactly what happens to your body when you run a marathon!

What Happens to Your Body During a Marathon?

One of the most popular tests of human endurance is the marathon. Globally, over 800 marathons are held every year, all of them over 26 miles long, attracting professional athletes and amateur runners alike. But exactly what are you willingly putting yourself through when you sign up to a race?

This is Unveiled, and today we’re answering the extraordinary question; what happens to your body during a marathon?

The modern marathon dates back to 1896 when the first modern Olympic Games were held in Athens, Greece. The event was inspired by the myth of Pheidippides, a messenger who ran all the way from Marathon Beach back to Athens to bring news of the Greek victory against the Persians in around 490 BC, over 2,500 years ago. The distance between Athens and Marathon was actually around 25 miles, and the earliest Olympic marathons differed slightly in length… but from the 1924 Games onward, the marathon has always been 26.2 miles (that’s just over 42 kilometers). Initially conceived as a big, flagship event for the rebranded Olympics, marathons have appeared at every iteration of the Modern Games. They’re also annually held at hundreds of locations all around the world. Some of the biggest include those at New York, Paris, Tokyo and London, which all attract tens of thousands of participants and just as many spectators. Away from the major cities, you might opt to run slightly more obscure races like the Great Wall Marathon in China, the ET Full Moon Marathon close to Area 51 or the North Pole Marathon across, well, the North Pole!

But just because lots of people do them doesn’t mean they’re easy – far from it. Marathons are incredibly taxing and almost all advice says that if you don’t train properly for weeks and months beforehand, you could be putting yourself at serious physical risk just by taking part. That’s because of all the remarkable things your body has to do to get you through the race. One of the first things to happen, which continues for the duration of the run, is that your heart rate and body temperature increases. Your heart rate can jump to as high as 140 beats per minute (or more), much higher than the average BPM of an adult at rest, which is between 60 and 100. Professional athletes train to have a slower heart rate, but even theirs is also going to get a big boost as their heart works overtime on race day. Meanwhile, body temperatures also, inevitably rise, sometimes to as high as 103 degrees Fahrenheit - the same as you might experience during a severe fever. This is one reason why runners use Mylar blankets (those shiny, foil sheets) at the end of the run; if they don’t, they run the risk of developing hypothermia as their bodies drastically cool.

The condition you’re perhaps most at risk of while running a marathon, however, is dehydration, simply because of the sheer exertion you’re putting yourself through. Luckily this is also one of the easiest things to avoid as long as you make sure you’re drinking enough water throughout the race, but even so it is relatively common for runners to suffer kidney problems. Kidney injuries will likely clear up eventually, but it’s important that runners are aware of the issues that can happen - and hydrate themselves appropriately. Equally, though, your sodium levels can also drop during an hours-long race, and sometimes severely… This is called hyponatremia and can be caused by drinking too much. It’s important to maintain a balance.

Another thing you could well run low on is sugar. Sugar is so vital to runners as an energy source that you can buy special, soluble sugar products just for exercise like this. To make sure they have enough energy to start with, runners stock up on carbohydrates for two to three days before the race and then use sugar - often in the form of energy gels - to get them through the day. If you don’t do this you’re at risk of hypoglycaemia - or “low blood sugar” - which can cause you to faint or throw up, and leaves you much more likely to hit the infamous “runner’s wall” – which happens when your body runs out of fuel and starts burning fat for energy. Tactically speaking, you can also avoid “the wall” by saving most of your energy for the final push. With the excitement and adrenaline of the start line, it can be difficult not to go off too quickly, but most coaches and experts agree that it pays to start steady.

We will get to the benefits of marathon-running shortly (there are plenty!) but, finally, there’s the risk of plain and simple injury. One of the most common and well-known injuries that runners experience is that their toenails can fall off. But, just in general, running this distance means putting your feet through a lot. Something as simple as a blister could ruin your entire race, which is why most runners take a lot of time choosing their footwear - getting the right shoes, soles and socks for them. Running 26 miles on a blood blister is no-one’s idea of fun! Then, even the best athletes are at some risk of a break or sprain; your bones, muscles, tendons and ligaments are, after all, being made to work very hard. Some pro-runners, after years of developing minor injuries to their skeletons and soft tissues, suffer aches and pains in later life. Meanwhile, because your body gets so busy trying to heal and cope with the exertion of what you’re doing, almost anyone who runs a marathon could be briefly compromising their immune system - meaning you’re slightly more likely to catch a cold after the race (another reason for those Mylar blankets).

But, of course, marathons – like all exercise – are generally hugely beneficial to people who run them. The long training period helps many runners get in the best shape they’ve ever been in, and some studies report that running a marathon can even add years to your life by “reversing the aging” of blood vessels. If you’re careful and well-prepared, running a marathon could be one of the best decisions you ever make, and few people who do it will ever come to regret it. Marathons can increase the health of your heart and cardiovascular system, they can strengthen your bones and muscles, they can help you lose weight if that’s one of your goals, and if nothing else they’ll give you a big boost of endorphins and a sense of achievement like no other. The “runner’s high” is a very real thing, and while scientists disagree on exactly what causes this post-workout (or sometimes mid-workout) euphoria, it basically amounts to chemicals and hormones in your brain and body that make you feel good. Some runners even report that any pain involved in completing a race feels like “good pain” - like something that isn’t detrimental to themselves. It’s feelings like this which keep runners going for all 26 miles and which motivate amateur runners to do marathons for fun. In general, if you complete the marathon, you’ll likely end it healthier and happier than when you started.

Although, that’s not to say that the recovery period is enjoyable... More often than not, it isn’t. First, there’s the issue of sleep. You might think that in your post-marathon exhaustion you’d be able to sleep for days, but that’s not always the case. Throughout the race, your adrenaline is pumping, and the stress hormone cortisol races through your system all day, even hours after you crossed the finish line… which is why so many marathoners report a sleepless night straight afterwards. Despite being more fatigued than you’ve probably ever been, it’s expected for you to be tossing and turning as your hormone levels return to normal; so, don’t beat yourself up if you’re not able to pass out as soon as your head hits the pillow.

Once you do get to sleep, though, and awake the next morning, don’t expect to spring out of bed ready to do it all again. If the marathon itself was painful, the next few days might be even worse. Now you have DOMS to contend with - that’s Delayed Onset Muscle Soreness. DOMS happens to more or less everybody after a strenuous workout; it’s the stiffening of joints, the achiness of muscles and the general difficulty to move with any speed, all while your body sets about repairing and re-energising itself. DOMS can take up to a week to go away, but it doesn’t mean you’ve done anything wrong; it’s a completely normal part of the post-marathon process and just means you should take extra care (you might even want to schedule a day or two off work!). Even veteran runners need to take it easy after a big race, so there’s really no over-exaggerating the importance of letting yourself rest. Drink lots of water, eat well and closely monitor how you feel, and you’ll be talking yourself into signing up for another race before you know it!

It’s estimated that just 0.5% of the US population will run a marathon at some point in their lives. It’s a similar statistic for most of the rest of the world. Marathon runners are a rare breed, and whether you’re healthy now but need a challenge, or want to use it as a way to get in shape, running 26.2 miles at least once in your life is almost always going to be a beneficial experience – even if it does take a lot of work and pain. And that’s what happens to your body during a marathon.