Top 6 Reasons Your Legs Feel Heavy During Running

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Wondering why do your legs feel heavy when you run? Then you have come to the right place.

The aching, tired, and painful legs while running are not just incredibly frustrating but may also discourage you from running.

There’s a number of reasons why your legs might feel heavy during running. These reasons vary from one runner to the next.

That’s why it’s not always easy to determine the exact cause without knowing more about your symptoms as well as your training approach and history.

Worry no more.

In today’s article, I’ll dig into the causes of heavy legs when running as well as offer some easy fixes and prevention guidelines.

Sounds great?

Let’s lace up and dig in.

A Beginner Runner

The reason your legs feel heavy during running may boil down to the fact that you just took up running.

A common mistake many beginners make is starting too fast and training at an above-average pace.

If you do this way before your body is ready for the intense exercise, you’ll, sooner or later, feel defeated and frustrated as your high expectations won’t match the reality on the ground.

The Solution

If you’re a beginner runner, do the following to ease the leg heaviness.

Start Slow

Pushing your body too far (or too hard) early only will bring you nothing but pain.

Instead, focus on starting slow then increase intensity (distance and speed) gradually. Don’t know how to get started? Check my beginner’s guide.

Schedule Recovery

Rest days are as important as your training days. Space out your runs with at least 24 to 48 hours of rest. The harder the session, the more recovery you’ll need. Your legs will thank you for this, believe me!


Another reason your legs might feel heavy during training is that you’re overtraining. This is a fact even if you’ve been training regularly for the past 12 months and are no longer in the beginner runner camp.

Overtraining typically stems from either pushing too hard on a certain workout and/or lack of recovery between sessions (usually, it’s a mix of both).

If you love to train hard, you’re not alone. But doing too much can be counterproductive in the long haul.

Other than heavy legs, other red flags of overtraining include:

  • Headaches
  • Decreased performance
  • Chronic fatigue
  • Mood swings
  • Illness, especially the common cold.
  • Appetite loss
  • Motivation loss

Take the following measure to keep overtraining risk at bay.

More Recovery Days

If your workout routine is consistently leaving you with dead legs, and you’re not properly recovering, consider adding in some extra off days.

Sure, recovery days may not add up to weekly mileage totals, but they’re equally important.

You should also repeat the same training pattern the week before moving to the next level.

You don’t have to sit on the couch and do nothing during a recovery day. Try active recovery. Go for a walk, a swim, an easy cycle ride, or lift weights at the gym. Yoga is also a wonderful recovery tool for runners.

Leg Day

Another reason you might be experiencing fatigue and heavy legs is that you’re doing too much strength training.

Strength training is a key aspect of efficient and pain-free running. You need total body strength to run—and perform—at your best. I cannot emphasize this enough.

However, strength training can take a toll on your muscles, especially when you target your lower body muscles—some of the largest muscles in the body. The larger the muscle, the more recovery time it will need.


Instead of doing ten sets of 8 to 12 reps of lower body exercise, try doing no more than five sets within the same range.

By doing less, you’ll allow your body to adapt and get stronger. Also, by reducing the overall demands, you’ll make it easier for your body to bounce back and recover.

Choose The Right Weights

You’re aiming to build strength while lifting weights but make sure to also account for your running. This is especially the case when running (endurance), and not resistance training (strength), is your priority.

Diet Deficiency

If you’re not a beginner runner, aren’t overtraining, or didn’t lift any weights, then low iron levels might be the reason behind the heaviness.

An iron deficiency—and diet imbalances in general—could drastically contribute to the condition. Therefore, try to fix any diet gaps you have by consuming more nutritious, whole, and natural foods and see if that helps.

More specifically, research has shown that low iron levels may cause restless leg syndrome. This is a neurological disorder that can cause leg heaviness, therefore, will limit your running performance.

Take the following measures.

Get Screened

Experiencing heavy legs during running as well as overall fatigue?

Then it might be time to check with your doctor. A simple blood screening may help you rule out any underlying imbalance, especially iron deficiency. Next, your doctor will set you on the right treatment course.

Eat Right

The treatment might be as simple as consuming more iron-rich foods or taking iron supplements until your levels are back to normal.

Some of the best iron-rich foods include red meat and beans

Wrong Shoes

Are your shoes too tight and/or worn out? They might blame

Your footwear choice can also affect how comfortable—or uncomfortable—you feel during training.

A pair of ill-fitting shoes may impact your technique, increase muscle and joint load, and contribute—even cause—pain and injuries in your legs.

Get The Right Shoes

Head to the nearest running specialty store and ask the staff to help you pick a pair of shoes that fits your foot type, running style, and training goals.

The 400-500 Miles Rule

All running shoes have a definite lifespan, which is roughly 400 to 500 miles of road work. Keep track of your shoes and start looking for a new pair once your current kicks reach that mileage range.

Wiggle Room

Leave at least a half-inch of space between your longest toe and the end of the shoe. You should be able to wiggle your toes inside of the toe box without feeling contracted.

Hot Weather

Running in the heat? The scorching temperature could be the reason.

Here’s the truth.

As you log in the miles, you’ll naturally sweat more, which makes you more and more hydrated the farther you run.

Dehydration makes your blood thicker, which makes it harder to pump. Thus, you feel leg heaviness during (and after) running.

Drink Plenty

Whether you train in the cold or hot weather, remember to stay well hydrated and to replenish your electrolytes.

Drink enough water during the day and replace lost body fluids. Check my full guide here.

Consult your Doctor

If you’ve taken all of the above measures but still experience chronic leg heaviness when training, it could be time to consult your doctor. They should be able to help you rule out any deficiencies or underlying conditions that could explain your condition.

The rest is just details