From your muscles to your mood, this is everything that happens to your body when you run 5km – and how you can help your body recover when the run is over.
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💪 YOUR MUSCLES START WORKING
You should begin with a warm up before your run, including some mobility exercises and drills, as these will help to get your body and mind ready to move.
When you start running, lots of different muscles will be activated, and each one has a different role to help you move forward. As you speed up, more blood is pumped to the muscles. The blood carries oxygen we breathe in to give energy to your muscles.
Your leg muscles do most of the work when you’re running, from your feet, calves, quads, hamstrings, glutes, hip flexors, plus the abs and even some in the upper body (plus the heart of course, but we’ll look at that separately).
Having strong muscles can really help improve your 5k run.
♥️ YOUR LUNGS AND HEART WORK HARDER
Your lungs bring oxygen into the body for energy. When you run a 5k, or do any exercise where your muscles work hard, your body needs more oxygen. As that exercise gets more challenging, we breathe quicker and deeper to ensure we’re bringing in enough oxygen.
If you want to know more about breathing when running, then check out this video!
Oxygen moves into the bloodstream and is pumped around the body by the heart, which is another very important muscle that starts to work harder when we run.
As the blood moves around our body, red blood cells carry the oxygen to the muscles. To deliver oxygen quicker, your heart contracts faster to increase blood circulation, which gives you a higher heart rate. The harder you run, the faster your heart beats to ensure the muscles get the oxygen they need.
Your heart also pumps other important things around your body like water which we eventually sweat out (more on this later!).
The fitter you get, the more efficient your body gets at utilising oxygen (learn more about VO2 Max here) and that makes harder efforts feel easier – basically our maximum heart rate remains the same, but we’re able to work harder and run faster below that maximum.
🍌 YOUR BODY USES FUEL
To be able to run in the first place your body needs energy.
When you’re running fast, your muscles use carbohydrates as fuel the primary fuel. Carbs are broken down into glucose which is then stored in the muscles (and some in the liver) as glycogen, which creates energy for the cells inside the muscle to use.
The rate at which glycogen is depleted depends on the intensity and duration of your run, but you won’t use all your glycogen on a 5k run (unlike the potential to ‘hit the wall’ in a marathon).
You shouldn’t need to fuel mid-run for a 5k, but it’s a really good idea to have an easily digestible carb-based snack before you run.
💦 YOU START TO SWEAT
As your breathing increases along with heart rate, your body warms up. It doesn’t want to overheat, so to stop that happening we begin to sweat. Water is carried in the blood and the body pumps more of it towards the skin, where sweat ducts pull the water out of the blood and onto the skin where it evaporates, which helps cool us down.
The longer you run, or the hotter the weather is, the more you’ll sweat. If it’s particularly hot, or you’re on long run, then you might want to take water and electrolytes with you on your 5k, but if not then ensure you begin the run well hydrated and rehydrate properly after the run. Here’s a guide to why runners need electrolytes and how to carry water when you run.
🥳 YOU FEEL GOOD (HOPEFULLY!)
As you’re running your 5k, your body will start to release natural chemicals called endocannabinoids, which give you that ‘runner’s high’ feeling that you may have heard about, and which until fairly recently was attributed to endorphins. It’s a short burst of exercise euphoria that helps you feel good and relaxed.
This release of chemicals in the body can also stop you from feeling muscle pain and general discomfort while you run, which helps you to keep going to the end (and hopefully encourages you to run again sometime).
Watch Sarah and Mo’s look into the ‘runner’s high’.
🫸 AND WHAT HAPPENS WHEN YOU STOP RUNNING?
You’re done! You feel good for finishing your 5k and within about 10 minutes you’ll notice your breathing return to normal and your heart rate go back down to a regular rate, and you’ll also stop sweating.
Now is a good time to rehydrate, especially if it’s hot (and don’t forget to add electrolytes) and eat something to refuel after your run – focus on a balance of protein and carbohydrates after a run.
Then, thanks to those ‘feel good’ endocannabinoids released by your body during your run, you’ll feel more energised and be in a better mood, which is always a good thing, and you’ll experience neurological perks such as improved memory and focus, and a better ability to switch between tasks, which is especially useful during the working day!
Later in the day, or over the coming days, you may feel soreness and aches in the muscles, which is because exercise causes micro-tears in the muscle. Your body will start to repair these after your run, and they’ll grow back stronger, helping you feel fitter – but listen to those aches and take it easy to help your body recover.
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