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Heavy legs when running: 8 common causes + 4 simple fixes


Tired, achy and heavy legs when running is a discomfort that discourages many runners from going for a run.

If you’ve ever felt like your legs are tonne weights, then you’re not alone.

The truth is many runners suffer from heavy leg syndrome at one time or another. The secret is not to let it put you off running for good!

If your legs regularly feel heavy when running or if your legs feel heavy and weak after running, then this could be a sign that you need to re-evaluate your training routine and how you approach your runs.

The good news is with a few simple fixes, you can regain your running mojo and energy during training.

In this guide we’ll explore:

  • 8 reasons why your legs feel heavy when running
  • 4 simple fixes to prevent heavy legs when running


Let’s get started!

heavy legs when running

8 reasons why your legs feel heavy when running

You may be wondering:

  • “Why do my legs feel heavy when running?”
  • ”Why do my legs feel heavy and tired when running?”

Poor running form, dehydration, iron deficiency and overtraining have all been attributed to sore and heavy legs.

Here is a list of potential causes of heavy legs when running:

  1. Overtraining
  2. Not allocating enough time for recovery
  3. Poor running form
  4. Lack of sleep
  5. Poor nutrition
  6. Poor circulation
  7. Dehydration
  8. Iron deficiency

#1 Overtraining

For the majority of runners, heavy legs when running is normally associated with their training.

If you’re training for a long distance event, for example, the number of miles you’re running each week can sometimes contribute to that ‘heavy legs’ feeling.

If you’re overtraining (e.g. running too many miles each week or not giving yourself enough time to recover in between runs) your legs may feel heavy as a result.

Overtraining, however, is not always linked to a high volume of mileage in your training plan. It can also be linked to training plans that progress too rapidly or take large jumps in training plans.

Trying to do too much too soon after an injury or break in running is also a common cause of overtraining. 

More often than not, overtraining can lead to illness and injury, so don’t be tempted to power through it! Instead, take a step back for a few days and reduce your overall training until you start to feel better again.

Listen to your body and really tune into how you are feeling on your runs.

Related: 11 symptoms of overtraining: How to overcome running fatigue

#2 Not allocating enough time for recovery

Another common cause of heavy legs when running is not allocating enough time to recovery in between runs.

If you’re someone that skips the post-run cool down, ignores active recovery in between runs, or worse doesn’t take rest days seriously, then this could be the reason why your legs feel so heavy.

Related: How to recover after a long run

#3 Poor running form

Improper running form is a major contributing factor to heavy legs when running.

Running form is all about running in the most efficient way possible. It looks at everything from your posture to your footstrike.

The truth is, poor running form, especially when it comes to your posture, footstrike and cadence, can put extra stress on your body which in turn can cause tired and heavy legs when running.

You can read my guide on proper running form and technique, but here is a brief summary of each area:

  • Posture. Good posture when running is important to ensure you don’t create imbalances in your muscles and joints when running, which can often lead to injuries.
  • Footstrike. Your footstrike is basically how your foot hits the ground when you run. There are three main types of footstrike: heel strike, mid-foot strike and forefoot strike. All three footstrikes can be used in different ways and on different terrains, and whilst there isn’t a clear favourite in the running community, the mid-foot strike is seen as the ‘happy medium’.
  • Cadence. Cadence is essentially how many steps you take per minute (SPM) during a run. The optimal running cadence is around 170 steps per minute. If you have a low cadence, you will likely have a long stride which means you overstride when you run. Overstriding is when your foot lands in front of your body when running, which is something you want to try and avoid as a runner as it can cause stress and pressure in your legs.

Related: The essential guide to head to toe running form and technique

heavy legs when running

#4 Lack of sleep

Lack of sleep is linked to many conditions that can impact your running performance, including tired and heavy legs when running.

A 2014 study on the relationship between sleep and exercise concluded that sufficient sleep is essential for the restoration of nervous, immune, skeletal and muscular systems.

Adding that virtually all bodily systems are impacted by poor or inadequate sleep.

Most athletes need between seven to nine hours of sleep each night. Trying to power through a run with just a few hours of sleep is probably not a good idea!

Make a good night’s sleep your priority. If your lifestyle means you can’t get at least seven hours of sleep at night, short afternoon naps may help training feel easier and improve performance.

#5 Poor nutrition

Nutrition is really important when it comes to being able to run consistently, week in week out.

Carbohydrates are a runner’s best friend when it comes to running long distances, particularly complex carbohydrates.

When you consume carbs, your body converts these into energy (also known as glycogen) which your muscles then use as an energy source.

If you do not eat enough carbs before a long run or distance event, your body won’t have enough fuel to sustain the required energy levels during the run, which causes tiredness, fatigue and that familiar heavy legs feeling.

Related: Carb loading for runners: Foods to eat and mistakes to avoid

#6 Poor circulation

Poor circulation can be a cause of heavy and tired legs when running.

When there isn’t enough blood circulating to your muscles, there isn’t enough oxygen to convert into energy.

This normally happens when you’re overexerting yourself and trying to run longer distances when you may not be ready.

heavy legs when running

#7 Dehydration

Hydration is critical to any form of exercise, whether it be a long run or a quick HIIT workout in your living room.

Of course, the levels of hydration required differ with each form of exercise, but the end goal is always the same: to replace fluids lost through sweat.

Dehydration, or not drinking enough water, is associated with muscle cramps, fatigue and a dry mouth. If you’re dehydrated, you might feel like your legs are more tired than usual or the run just feels harder. 

To combat this, tune into your body and drink enough fluids throughout the day so you don’t feel thirsty. 

If you’re exercising more than normal, then it’s important you adjust hydration according to your activity levels. The weather may also mean you need more fluids on those hot runs. 

Related: Hydration and running performance: 4 key hydration tips for runners

#8 Iron deficiency

If you regularly experience tiredness, fatigue and heavy legs when running, then it’s worth checking your iron levels.

Iron deficiency means your body has a more difficult time supplying oxygen to your muscles on a run, which can result in a heavy leg feeling.

Most runners get enough iron in their diet, however there are times when your eating habits may mean it’s more challenging to get the recommended intake. 

With a vegetarian or vegan diet, it’s important you eat a variety of iron-rich foods such as dark leafy vegetables, pulses and wholemeal bread to maintain your iron levels. 

Iron supplements in the form of a daily tablet are also an option but shouldn’t be your only source of iron. 

If you’re a female runner, then your period may mean you’re at a greater risk of iron deficiency, especially if you suffer from heavy menstrual bleeding. 

A quick blood test with your GP will help you identify if you’re suffering from iron deficiency. 

heavy legs when running

4 simple fixes to prevent heavy legs when running

#1 Warm up before each run

The warm up is important to prepare yourself mentally and physically for the run.

A proper warm up consists of two main parts:

  • Jogging
  • Dynamic stretches

Both of these will help you mobilise your muscles and joints before a run.

Related: 9 quick and easy dynamic stretches to do before a run

#2 Cool down after each run

If you suffer from tight or stiff muscles or muscle soreness, then a cool down after a run will help to bring your heart rate down and stretch parts of your body involved in running.

Cool down stretching (also known as static stretching) is when you hold the stretch to the end of its range of motion for roughly 20 to 45 seconds.

Try and give yourself 10 minutes at the end of each run to bring your heart rate down and stretch parts of your body involved in running. 

Your quadriceps, hamstrings, glutes, hips, back and arms are all utilised when running. Make sure you target each muscle group to help alleviate any soreness or pain. 

Here are some sample stretches that you can do as part of a cool down. Hold the stretch for at least 20 seconds before moving onto the next stretch:

  • Deep lunge stretch
  • Standing quad stretch
  • Standing adductor stretch
  • Standing TFL stretch
  • Lying gluteal stretch
  • Standing calf stretch

Related: The best cool down stretches to do after a run

#3 Foam roll

Foam rolling is another great way to alleviate muscle stiffness and soreness after a run.

One of the foremost benefits of foam rolling is that it improves circulation and increases blood flow to your muscles.

The other benefit to foam rolling is that it loosens up your muscles. If you have stiff muscles, it makes it harder to perform on long runs and shorter, speedier runs.

Consider including foam rolling as part of your warm up before a run and cool down after a run.

Related: Foam rolling benefits for runners

#4 Wear the right running shoes

A good pair of running shoes that support your feet are essential when running longer distances.

You can find more information in my guide on how to choose the right pair of running shoes, but you’ll want a pair of running shoes that support your feet when you run and provide flexibility and durability.

More tips on recovery and performance: