Why do my legs feel heavy and tired when running? (2024)

Have you ever felt like your legs are made from lead weights? Or like you’ve got bricks attached to them, weighing you down with every step? You’re not alone.

We’ve all experienced heavy legs when running. It’s frustrating and can be demotivating – but it’s usually only temporary. So, if you find that you’re asking yourself “why do my legs get tired so quickly when running?”, then keep reading to find out the possible causes – and what to do about it.

Do you have rest days scheduled into your plan? Recovery from a run is just as important as the run itself. Both your body and your brain need a break – and without proper rest, you could risk injury, fatigue (both mental and physical), or even burnout. Every training plan should have at least one rest day per week, depending on what you’re training for and how much running experience you have.

As well as rest days, it’s important not to run all of your runs super hard. It might make your Strava stats look good, but you’ll be hurting your progress. Your easy runs should be easy, allowing you to recover from harder runs while maintaining your aerobic fitness. If you keep the pace easy, it’ll help to prevent your legs feeling like lead after running and allow you to put your effort into your long runs and speed sessions.

Let’s face it, sometimes we’re all guilty of skipping the warmup and heading straight out the door… But the truth is that both pre- and post-run stretches can really help to reduce runners heavy leg syndrome. Both can help to decrease muscle stiffness, making you feel sprightlier and less like you’ve got dead weights attached to your legs.

You don’t need to devote hours and hours to stretching, but your legs will thank you for taking 5-10 minutes before and after your runs. Your pre-run warm up should be focused on dynamic stretching – think walking lunges, leg swings, walking on your tip toes, bum kicks and high knees. Post-run, you should do dynamic stretches, focusing on all the muscles that have just worked so hard during your run, like your quads, hamstrings, hips, glutes, calves and back.

Another reason for tired legs could be related to your running form.

Poor running form may cause some muscles to work harder than they should. Overstriding (when your foot lands too far ahead of your body), for example, can put excessive strain on your calves and quads. That means they may tire faster than they otherwise would, which can make them feel tired and heavy. Or, if you heel strike (where you hit the ground with your heel first rather than your forefoot), it can send more impact through your leg which can, again, lead your joints and muscles to fatigue faster. If one leg feels heavy when running but the other is fine, it may mean that one of your legs isn’t as strong as the other, or it could highlight biomechanical differences which are leading to poor form.

Improving your running form will help you to work more efficiently and decrease the risk of tired legs. You may want to get your form checked by a specialist who can check for any issues and advise you on ways to improve.

Alternatively, keep these tips in mind:

If you eat a low carb diet, it could cause heavy legs. But how can a lack of carbs cause dead legs? Well, carbohydrates are stored in our muscles as glycogen, and when we run, our bodies use these glycogen stores to fuel our muscles. If your glycogen stores are low, your muscles may not have enough energy to perform meaning they’ll feel heavy and fatigued. So, if you’re not eating enough carbohydrates to provide plenty of energy, it’ll be harder for you – and your muscles – to get through a run. Try to eat a healthy, well-balanced diet that includes healthy sources of carbohydrates like fruit, vegetables and whole grains and you should find yourself with plenty of energy – and legs that are less fatigued!

Another dietary deficiency that can lead to tired legs is a lack of iron. Iron plays an important role in transporting oxygen to your muscles – so if you’re deficient in iron, it’s harder for your muscles to get the oxygen they need. That means they can feel tired and heavy, and since you mostly use your legs when you run, this will translate to the dead leg feeling. Iron is also important for muscle repair and recovery after exercise. If you’re not getting enough iron, it can delay the recovery process, meaning your muscles feel sore for longer. Some great dietary sources of iron include red meat, beans, poultry, and dark leafy greens like spinach and kale. You can also take iron supplements – but if you suspect you’re iron deficient, it’s always a good idea to check in with your doctor for proper evaluation and guidance.

Are you drinking enough? If you’re dehydrated, it can cause all sorts of problems, from headaches to muscle fatigue. The importance of staying hydrated can’t be overstated, and if you’re not drinking enough – whether before your runs, during your runs, or afterwards – it can cause heavy legs.

Dehydration can decrease blood volume, meaning there’s less blood circulating around your body. That means your muscles may not get enough oxygen and nutrients when you’re running, causing them to feel tired. Being dehydrated can also disrupt the balance of electrolytes in your system, including calcium, magnesium, potassium and sodium – all of which are important for muscle contraction and nerve function. If you don’t get the right mixture of electrolytes, it can cause cramps and tired legs.

Try drinking to thirst throughout the day – but if you need a little extra help, you could set a reminder on your phone telling you to drink every so often. And remember that you’ll need to drink more in warmer weather! You may also want to start using electrolyte drinks to ensure that you’re getting everything you need. If you’re running for an hour or less, plain water should be fine – but for longer runs, electrolyte drinks can be beneficial.

If you’re not getting enough sleep, your body will let you know about it. When you’re tired, your muscles can feel heavy – and you might also find it more challenging to maintain proper running form, which can further contribute to your heavy legs. What’s more, when you sleep, your body releases hormones that support muscle recovery. So, if you’re not getting enough shut eye, you’re doing your recovery a disservice. And inevitably, if your muscles aren’t getting a chance to repair themselves, they’re going to feel heavy and fatigued.

Everyone needs a different amount of sleep. It’s often said that adults need 7-8 hours of sleep a night, but some people function fine on 6 hours and others need 10 hours. Find out what works for you – and then make sleep a priority. You should also try to maintain a consistent sleep schedule, aiming to go to bed and get up at roughly the same time each day, and improve your sleep hygiene by reducing the amount of screen time you have before bed, ensuring your room is at the right temperature and is dark enough for sleep.

When you get into a groove with your sleep, those 6am runs should feel much less painful!

Some people have poor blood circulation which can lead to fatigue and – you guessed it – legs that are tired when running.

Blood carries oxygen to your muscles, which is necessary for energy production during exercise. When you have poor circulation, it means that less of this oxygen reaches your muscles, and you get tired more quickly than if you had better circulation. If you think you have poor circulation, it’s best to speak to your healthcare provider for a full assessment, diagnosis and treatment options.

Heavy shoes, heavy legs. If you’re wearing the wrong shoes, you might be forcing your legs into doing more work than they need to! And it’s not just about how much your shoes weigh. If you’re wearing the wrong size, your shoes fit badly, or you don’t have the right support, it can cause bad form – which can, again, lead to tired legs or even injury.

There are loads of different running shoes out there, from lightweight shoes designed for speed, to soft, cushioned shoes that will support your feet over long distances. You can also get neutral options and shoes with built-in support to keep your body moving in its natural motion path. It’s just a case of finding the right shoes for you. Take our quiz to determine which shoes best suit your running needs, and you’ll be off to a flying start!