A marathon is an incredible challenge for your body and your mind, and a lot of things happen during the course of 26.2 miles, or 42.2km.
Here’s everything you need to know about what happens when you run a marathon, and here’s Sarah and Mo to tell you more.
A Bad Night’s Sleep
Yep, we’re starting before the marathon even begins, and because of the nerves and excitement of race day, and an early alarm, you probably won’t get much sleep the night before the race.
Do your best to sleep well in the week leading up to your marathon, and don’t panic about the night before. It’s unlikely to have a significant effect on your marathon because the adrenaline of race day will get you through (and some caffeine could help).
Get Psychologically Ready
You’re physically ready to run, but is your mind ready?
The day before the race you want to be prepared for what’s coming, and that means eating and drinking well, packing your kit (this pre-race checklist will help), and making plans for your race. Minimise the things you need to think about on race day because you need your brain to be focused on the run and not worrying about anything else.
Here’s some advice on working on mental resilience for runners. This can be really helpful ahead of a race, and also when the run starts to get tough.
Your Muscles Start Working & Your Heart Rate Increases
It’s race day, you’re at the start area, and hopefully you’ve done a warmup. For you that could be a jog and some strides, or just some dynamic movements. Do whatever you need to feel like your body is ready to run.
As your race begins, your muscles start to work harder to move you forward. The primary running muscles are in the legs, but we also use a lot of muscles in the core and upper body, especially to stabilise us, which is why our lower back and abs can ache late into a long run.
Your heart rate and breathing will increase as you run and this is because you now have a greater need for oxygen.
When you inhale air, your body absorbs oxygen into your bloodstream. Your heart pumps blood around your body to your muscles, delivering the oxygen which you need to create energy. Blood also carries other important things like energy in the form of glucose (more on that later).
The harder you run, the more oxygen you need to breathe in, and your heart rate and breathing rate both increase. And the harder you work, the more you sweat…
You Start To Sweat
Exercise creates heat in the body, and we cool ourselves down by sweating (see more about the science of sweat here). As blood is sent to the muscles to give them oxygen and fuel, it’s also pumped towards the surface of the skin, where it passes sweat glands which remove water from the blood and send it to the skin. As sweat evaporates, we feel cooler.
An average person will lose 3-6 litres of sweat during a marathon. Some people naturally sweat more than others, while hot weather will have us sweating more heavily than cold weather. Because we sweat, we need to rehydrate to avoid dehydration…
We Need To Hydrate
Don’t drink to thirst in a marathon, and instead focus on sipping little and often during the run. Aim for 500ml per hour, and more if you can tolerate it, to reduce the risk of dehydration (this is something you need to practise in training).
Most road races have water stations every 1-3 miles/2-5km (they may be further apart in trail races), or you could carry your own water in a soft flask, bottle or hydration vest if you prefer.
Avoiding dehydration is very important. When we’re dehydrated, we have less blood volume so the heart has to work harder to pump enough blood around the body, which makes running feel so much harder. Other symptoms of dehydration include feeling nauseous, dizzy, weak and confused, and it could lead to more serious problems which may stop you from finishing your race.
But be careful: it’s possible to drink too much water, and a condition called hyponatremia can be extremely dangerous. This happens when we dilute our body’s electrolyte balance, so you should take electrolytes with water before and during a marathon.
You Might Need To Use The Toilet
You’ve drunk a lot of water leading to the start line, and even though you used the toilet a few times before the gun went off, there’s a chance you’ll need to go again.
No matter how fast you hope to run, if you have to go, then it’s best to just stop. Taking one minute to use a portaloo on the course will save you from a lot more discomfort later in the race.
We Use A Lot Of Energy, And We Need To Take On More
The body’s primary fuel source is glucose, which we get from carbohydrates. We carb-load in the days before a marathon, meaning eating extra carbohydrates, and our body stores as energy. It’s like starting a long drive with a full tank of petrol.
But like a car, we can only store a finite amount of fuel before our tank gets empty – and our body can’t physically store enough to last for a full marathon. When we run out of energy, we hit The Wall.
‘Hitting The Wall’ is when we no longer have enough glucose left for fuel, so our body has to resort to using fat as the fuel, which is much harder to utilise (basically it takes lots of oxygen to turn fat into energy, meaning most of the oxygen we breathe in has to be used for that, and our body is forced to slow down).
To help avoid The Wall, we need to be taking on energy while we run. And we should start doing it early and often.
Most people choose energy gels, energy chews and energy drinks as they are the most efficient fuels and the easiest to digest. You’ll want to aim to take in 30-60g carbs per hour as a minimum (faster runners will want 60-100g). Try to take a gel every 4 miles or 7km (this is something that it’s essential you practise during long training runs).
Here are some alternatives to energy gels and a carb calculator for your race and training.
The Middle Miles
There’s an old saying that ‘A marathon begins at mile 20’ (or 32km for metric folk). It means that if you’ve trained right, then getting to 20 miles should be ok, but the final six miles (10km) are going to be tough as your body is tired, you risk Hitting The Wall, and everything just generally hurts.
That saying is pretty accurate, but you still need to actually run those first 20 miles.
You should aim to maintain a steady pace. You don’t want to be speeding up and slowing down, as that can add extra strain on your body. If you can be consistent then your body can settle into the pace, and your heart rate and breathing can remain constant, which is going to help in a marathon.
The run should feel ‘easy’ in the first half. You can always choose to speed up later, whereas slowing down is never something you choose to do – it’s something you have to do because your body can’t carry on at the same pace.
In these middle miles it’s important to not get overwhelmed…
Don’t Focus On The Whole Distance, And Break It Down
While it’s natural to count down the distance that’s left in the race, that can come to feel overwhelming and extra challenging as the run gets harder. You might immediately feel happy to see mile marker 16, but knowing you’ve still got 10 miles to go can feel like a long way.
Break the race down into 1km or 1 mile chunks, and focus on maintaining a good pace for just that one block of distance. ‘Run the mile you’re in’ is another well-known marathon saying and it can be really helpful to make you focus on how you’re feeling right now, not on what’s coming later in the race.
You May Feel Sick
This one sucks. When we run, our body prioritises getting blood to our muscles to keep us going, and that means it deprioritises other parts of the body, including the stomach. So when we try to consume liquid and energy gels, our stomach can struggle to deal with it, which can make us feel ill.
Starting a race well hydrated, including having electrolytes, can help. As can practising fueling during training to work out what is best for you.
If you do feel ill then slowing down is probably the only way to help you feel better. Sometimes nausea can pass quickly and all it takes is to ease off your pace for a few minutes.
Blisters and Chafing
Hopefully you’ll have practised wearing all of your kit in long runs so you know before a race whether anything might cause you any problems or discomfort, or you know to use tape, plasters or anti-chafe on particular parts of your body.
But different weather conditions – more heat, rain, humidity – or just the extra time it takes to run a marathon can cause issues you didn’t foresee.
Sometimes you may be able to stop at a medical tent to get some help – a plaster or anti-chafe – or you might just need to carry on and finish the run and worry about it later.
But if a blister or chafing (or something annoying like a stone in your shoe) changes the way you run then be careful as it could lead to injury somewhere else in your body. Deal quickly with anything that bothers you, especially if it changes your stride.
Muscles Get Tired, So Focus On Your Form
You’ve got to mile 20 or 30km and you’re still maintaining the same pace you’ve been running for the whole marathon so far, but it feels so much harder now.
You’re having to put in more effort to maintain the same speed, you’re breathing more heavily, your heart rate is going up. Fighting through fatigue is one of the hardest challenges in a marathon
Every step puts strain through your leg muscles. Over the duration of a marathon you’ll take something like 40,000 steps, and that damages and weakens the muscles, making it harder to run.
As you get tired and weaker, you may start to run with poor form. You’ll slump over, your stride gets shorter, cadence gets slower. Focus on running with the best form you can. If it helps, then imagine a piece of string coming out of the top of your head and think about that being pulled and making you run really tall and upright.
And it’s not just our legs which get tired…
We Can’t Think Straight, Or Start Having Negative Thoughts
As we get more tired, our thought processes become more limited, and can get more negative or confused, which makes it harder to make good decisions. Our brain uses around 20% of all the energy in our body, so we aren’t just taking on gels to fuel our legs, it’s for our head as well.
You have to fight against the negative mindset, because while you can’t do much about aching legs, you can use your mind to help you. Work on having a race mantra, or sayings which can help get you through if you start to feel negative thoughts. Be positive. Smile to yourself. Find ways to distract yourself.
Here Come The Cramps
You may start to feel cramping. It could be a deep ache that makes it hard to run properly, or it could be the dramatic type of sudden cramping where the muscle feels like it’s seized up.
Most cramping comes from general fatigue and it’s impossible to stop a cramp if it’s going to get you, but racing at a sensible pace can help you avoid (or at least delay) them. If you feel a cramp coming, then sometimes the best (or only) thing to do is stop and stretch. Being well-fueled and hydrated can help here, as can doing your long training runs which conditions your body to the distance.
The Final Mile
Whether you’re chasing a PB or just trying to finish, the final mile always hurts. It feels further than any mile you’ve run before. Your heart rate might be nearing its maximum. The pains are at their worst. You just want this to be over.
But the crowd support is also some of the best. Take in those cheers. Make sure you soak up the support as it can be a big boost in those final few minutes.
As you cross the finish line, something magical happens and all the discomfort disappears for a few wonderful seconds.
It won’t last long, so enjoy it while you can…
After The Race
The finish line feeling is an enormous mix of emotions. Many people start crying as soon as they cross the finish line. There’s joy and relief. Pride. Sometimes there’s sadness or disappointment at not achieving a goal.
As you stop running and start walking, your legs will feel unstable and weak. Your lungs ache from the effort. Your heart rate will remain high, but will gradually come down.
If you sit down, you might feel muscle cramps come on (and it’s hard to get back up again!).
You’ll be thirsty and will need to drink, but you may also struggle to eat for an hour or two after a marathon as your stomach settles (or you may be ravenous immediately!). Try your best to drink and take on some protein and carbs – even a protein shake or chocolate milk can be good.
For the rest of the day, try to keep moving to help stop your muscles seizing up. Eat and drink. Most of all, celebrate that you’ve done something amazing and you’ve run a marathon!
In the next few days, focus on prioritising your recovery. You’ll have aches, stairs will become your enemy, you may be extra tired or extra hungry, you may feel ill as your immune system is weakened, and you may feel sad that the marathon is over. Just look after yourself – here’s more on how to recover after a marathon.
Want to know something we haven’t covered? Here are the answers to more than 50 questions all about the marathon!
