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Why Is Running So Hard? 5 Reasons It’s Tough + Why You Should Push On

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Beginner runners often have two main questions:

Why is running so hard for me, and when will running get easier? If running feels hard, don’t worry, you’re not alone. Running is hard.

In this article, we will answer the questions why is running so hard, why is it so hard for me to run, and explore why running feels difficult.

More specifically, we will cover: 

  • Why Is Running So Hard for Me?
  • Why Is Running So Hard? 6 Reasons It’s Tough
  • Why Is Running Suddenly Difficult?
  • Is Running Worth It?

Let’s get started!

An exhausted runner with their hands on their knees.

Why Is Running So Hard for Me?

If you are a beginner runner who is asking the question, why is running so hard, the first thing you should know is that it’s totally normal to feel like running is hard and that every time you go running, you feel like you have to keep stopping to walk.

Running is hard. It is very demanding on your heart and lungs to take in and circulate enough oxygen and nutrients to your working muscles to keep up with the demand of your workout. 

When you’re a beginner runner, your heart hasn’t yet adapted to the aerobic challenges of exercise, so your heart rate often spikes very high, even when you’re jogging relatively slowly

Over time, your heart muscle will become stronger, and your blood plasma volume will increase. These adaptations make each heartbeat much stronger, ejecting more oxygenated blood to your body. This refers to an increased stroke rate.

When your heart pumps more blood per contraction, it can beat more slowly while still supplying the oxygen your muscles need.

This will help your heart rate stay lower, making it easier to keep running without stopping.

Similar adaptations happen in the lungs. As they get stronger, your tidal volume increases (the amount of air you inspire), which will help you breathe slower and more relaxed as you run.

Running is also challenging for your muscles and joints, especially in your lower body. It takes time to build up the muscular strength and endurance in your legs, so your legs might hurt or feel completely fatigued when you first start running.

A tired runner leaning against a wall.

Why Is Running So Hard? 6 Reasons It’s Tough

We all inherently know that running is difficult. That’s why beginner runners can’t just go out and run 10 miles on day one, and experienced runners have to spend months training for a marathon.

But why is running so hard on the body? Let’s take a look at the main reasons why running is so tough:

  • Your body is subjected to 2-3 times your body weight in force every time you land.
  • It’s a tough cardiovascular workout, so you breathe hard, and your heart beats quickly.
  • Running is a high-impact activity.
  • Running utilizes almost all the major muscles of your body.
  • Running uphill requires even more work.
  • Running can be mentally challenging and exhausting to stay focused, motivated, and positive.
A runner stopped on the trail in the snow, eyes closed thinking, why is running so hard?

Why Is Running Suddenly Difficult?

Once you’ve been running consistently for several months, you should find that running feels much easier.

You’ll be able to run longer without stopping to walk, and you might even be able to run faster, but more notably, running will feel less hard.

As the months go on and you keep up with your running routine, you’ll get into a groove where your runs may even start to feel invigorating, and you’ll feel strong for most of your run.

However, sometimes runners find running suddenly feels difficult even if they’ve been running consistently. But why is running so hard after all those years of training?

There are a few potential reasons why running may suddenly feel difficult even if you’re not a beginner, including the following:

A sweaty tired runner with a hand on their face.

#1: You’ve Increased the Intensity

Running is certainly going to feel difficult if you’ve ramped up your intensity, especially if the changes to your training were not gradual.

Have you started doing any hard running, like speed workouts? Hills? Longer runs?

Have you started running faster during your training runs every day?

The workouts you do are cumulative, such that your body needs time to recover between one run and the next. When you start adding hard running like speed and intensity to your training program, the stress on your body increases significantly even if you are not increasing your mileage significantly.

Speed workouts and long runs are much more taxing on the body than easy distance runs, so if you have added a bunch of interval workouts or are generally running faster for nearly every run, your body will be exhausted.

A tired runner, hunched over, hands on knees.

A general rule of thumb is that you should not increase your mileage from one week to the next by more than 10%

For example, if you run 20 miles one week, you should not run more than 22 miles the next week. The following week, you should not exceed 24.2 miles.

Abiding by these recommendations can help reduce the risk of injury by giving your body time to adapt to the gradual progression rather than shocking your tissues with jumps in volume.

It is more difficult to quantify the intensity of your workouts, so there isn’t such a clear-cut recommendation for how to progress while mitigating the risk of injury.

For instance, how would you increase the overall intensity of your weekly runs by 10%? Most likely, different workouts were performed at different paces.

If you can easily adjust your paces unilaterally by no more than 10%—say, if you run on a treadmill or are only doing distance runs with a GPS watch and always run at a steady pace—then this approach can definitely work.

However, most runners will find that their training paces for every workout in a week don’t fall neatly into one clear box that’s simple to adjust gradually.

Therefore, it can be hard to know how much you’re increasing the intensity of your overall training from week to week.

This is especially true when you first start adding speed workouts and intervals to your runs.

The best advice is to be mindful of increases in intensity and avoid increasing intensity and volume from one week to the next.

If you’re going to run more distance, keep the intensity the same. If you’re going to run faster or add hard workouts, don’t increase the distance as well.

Two beat runners lying on a court.

#2: You’re Not Fueling Properly

If you are asking yourself, why is running so hard, one of the primary reasons running can suddenly feel difficult is under-fueling

Your 24-hour nutrition is important. Not only do you need to fuel your body with enough calories and plenty of carbohydrates before your run, but you also need to ensure you’re eating well after your workout to facilitate recovery.

Aim to eat a post-run snack or meal within 30 minutes of finishing a run.

This can be difficult from a practical perspective for some runners, and many runners don’t feel hungry right after running.

Sports drinks, protein shakes, protein bars, or smoothies can be decent options in these cases.

A 3:1 or 4:1 ratio of carbohydrates to protein is ideal for your post-run snack. 

Your overall diet also needs to support your training. You need to take in an adequate number of calories for your body size and activity level and a good mix of foods from all the major food groups.

A tired runner, hands on hips, eyes closed.

#3: You’re Getting Sick

One reason running suddenly feels hard can be that you’re getting sick.

When your immune system is trying to fight off an infection or virus, a lot of resources and energy are going towards defending your body, so you’ll feel less robust and energized when you run.

If you’re feeling tired and run down in general, and not just when you’re running—especially if you have other symptoms—there’s a decent chance you may be getting sick.

#4: You’re Overtraining

Overtraining can occur when you increase your mileage or intensity too quickly or don’t take enough rest and recovery during and after your workouts.

Chronic overtraining can lead to overtraining syndrome, a condition marked by the presence of various physical and mental symptoms, such as sluggishness, low energy, appetite changes, hormonal imbalances, difficulty sleeping, irritability or other mood changes, poor immunity, and impaired athletic performance.

It’s important to note that your training volume and intensity must be considered in the overall context of your life when assessing whether you’re overtraining.

Rather than definitively being brought on solely by running high mileage or running too hard and fast, overtraining syndrome occurs when the volume and intensity of your training exceed what your body can handle in the context of all the other stressors and factors going on in your life.

If you have other stressors, such as work, moving, a new baby, a sick parent, etc., your body won’t be able to tolerate as much training while still recovering as quickly.

Our bodies only have a certain stress tolerance, and running is only one factor contributing to the overall stress. 

A tired runner, hands on knees, hunched over.

#5: Your Iron Is Low

If running suddenly feels difficult, it’s worth checking your iron levels.

Anemia and iron deficiency lead to fatigue, dizziness, breathlessness, poor endurance, pallor, and other symptoms in exhausted runners.

Iron deficiency is particularly common among vegan and vegetarian runners as well as female runners who menstruate. 

Plus, runners are prone to low iron because running is associated with something called foot-strike hemolysis, which refers to damage to red blood cells (which carry iron) from the impact of landing on your feet with each running step.

#6: You’re Not Sleeping Enough

It’s a simple fact that your body needs sleep to recover from your workouts and to give you the vitality and energy you need to run well and feel well.

According to the American Academy of Sleep Medicine and Sleep Research Society, adults need a minimum of 7-9 hours of sleep tonight. The needs of runners are usually somewhat higher.

Practice good sleep hygiene and set a routine to get enough sleep for your recovery and overall energy levels.

A tired runner leaning against a wall, hand on head.

#7: You’re Mentally Burned Out

Mental burnout with running is a real thing. You might be bored with your routine, stressed by your workouts, or just mentally exhausted.

Try mixing things up, running with a friend, changing your routes, or swapping in some cross-training workouts instead of running for more variety.

Is Running Worth It?

Even though running is difficult, most runners find that it’s totally worth it.

Running can change you: body, mind, and heart.

Physically, running helps you build muscle, strengthen your heart and lungs, improve your health, manage your weight, reduce your risk of disease, and become fit.

Mentally, running boosts confidence and self-esteem, reduces stress and anxiety, elevates your mood, improves memory and focus, and protects against cognitive decline.

In terms of your heart and spirit, running can make you a better person. You can set and achieve goals you never thought possible. 

You can make new friends, raise money for charities, spend time outside, and learn about yourself and the world.

If that’s not enough motivation to push through when running gets tough, try to think about what YOU love about the sport.

We are all on our own unique journeys. Let running take on whatever role in your life you’d like it to. Enjoy the run.

If you are feeling a bit low on motivation, we have a great list of inspirational quotes for you read through.

A runner hunched over on the ground.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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