I could run for 25 min straight…It’s only 15 min today…

I ran 5 miles last Wednesday…today only 2 miles and I’m so tired?

Why is my running endurance getting worse?

Are you finding yourself asking this question of late? Here are the common 5 reasons why your endurance is getting worse.


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Why is your running endurance getting worse

5 Reasons why your running endurance is getting worse

1. You are skipping slow long runs

I can tell this from my experience. After I finished my first 5K I was too happy.

I thought 21 mins of running time was great. However, I wanted to improve on that.

I followed the same 5K routine with only minor improvements.


I got stuck in the same plateau of around 28 mins.

The reason was beyond me and it was really getting frustrating. I not only couldn’t improve. I actually was getting worse.

I wanted to run a fast 5K but was going nowhere. And like you, I started Googling for reasons…

Too proud to ask for help you may say…

Most of the forums that I frequented, mentioned that skipping long runs or suddenly increasing pace can be a reason.

So I thought let’s try to go slow and long…and see what happens…

I picked up a half marathon training plan and started to train myself…

Little by little I saw progress and finally could run my best 5K with a sub 18 min PR.

If you are dealing with a plateau or a decreased endurance, try to go slow and for a longer duration of time.

You will be able to improve your endurance significantly…I promise.


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2. You are suffering from iron deficiency

This is also a frequent reason for a sudden decrease in endurance levels.

Many times, the symptoms are not very apparent. You may want to get your hemoglobin levels checked.

A simple blood test will be able to tell whether you are suffering from iron deficiency.

Another cause of sudden loss of endurance may be due to overtraining.

Your body will remain fatigued and you will be more prone to injuries.

However, there will not be very clear signs of fatigue.

Here also some blood tests may help you out.

Check for your Creatine Kinase or other inflammatory markers.

These will tell you if you have overworked your body or not.

3. The weather is hot

You may not realize it, but the weather may be hotter than last week or day.

This will increase your temperature way more during running and will also make you lose a lot of extra sweat during your run.


You will be more tired and you may not be able to run for the same duration of time that you did earlier.

Related: How does heat impact the running pace?

 In other words, you may think that your endurance has decreased.

In truth, it may not even be related to your endurance…

What should you do then?

Well, ask the Sun to be less hot… 😛


Just change the time of your run. Running early in the morning or later in the evening may be better.

Once you do that, check if your endurance is still reduced or not.

If not, then the weather was the culprit, otherwise check the above points to pinpoint the problem.

4. You did not meet your nutritional needs last week

If there is no apparent reason for your endurance slowdown, check whether you ate properly last week.

If we are not taking proper food and still try to run, your body will not show signs immediately.

However, give it a week or two, it will start to rebel and a common way of manifestation is the loss of stamina.

Related: How To Increase Running Stamina By Food? 

You may also find that you are getting more injured. Shin splints, knee pain, etc. will become common.

If this is the case, load up on calorie-dense foods like nuts. Also, take 48-72 hours of complete rest.

This will help you to recover from the injuries that you may have sustained and overtraining.

Why did I say overtraining?

Because most of the time overtraining is more to do with food or lack thereof.

Another common cause may be that you are not taking sufficient water.

Lack of water makes you tired more easily. So, aim to take at least 3 liters of water throughout the day to avoid endurance loss due to dehydration.

5. Your life is taking a toll on you

Many times the problem of sudden endurance loss may be more complex and has nothing to do with the above points.

Your life may be interfering with your performance. If you are unsure of what it is, try to take a look at the followings:

Sleep – Check if you are getting enough sleep or not. Sleep is the time when your body actively recovers.

If you are not sleeping enough, then your body will not recover properly. Then when you run or do any kind of intense workout, you are overstretching your body’s limits.

This will also make you lose your endurance.

Stress – This I consider to be the mother of most of our health problems. Couple of years back I was detected with a higher resting pulse rate than average.

It was somewhere in the range of 110 bpm when I was doing nothing. WHOA! My doctor warned me that, I’ll be facing higher blood pressure if I’m not serious about my fitness or my overall health and eating habits.

But what could I do? My work pressure was too much and my mother became very sick at that time.

I’m too attached to my mom and having to stay away from my family took a toll on me. And enter my higher heart rate.

As you know, if your body is not functioning properly you will not be able to perform at your fullest. Hence the lower endurance level.

Adrenaline fatigue – This is a byproduct of your stress. However, this may also happen if you over train. Your Adrenaline gland will have overdrive and you will be too tired to deal with anything, let alone workout. And suddenly you are slow.

Since the above issues are more complex for a quick fix, you will have to take a hard look at your life. Sleep deprivation may be relatively easier to fix, however, stress may not be. If you cannot immediately reduce your stress, please start doing meditation. 

You may perform meditation while running as well. And meditation doesn’t always have to be when you are seated. You can lie down and perform Savasana. A good 20 min of Savasana is said to be equivalent to 4 hours of sound sleep. It will also relatively reduce your level of stress.

Here is an effective practice that you may perform:

Maintaining your running endurance may be a challenge. There are many factors that contribute to them. Some are easily rectifiable and some are not. If you want to keep maintaining your running stamina and get better here are some running tips for you.

Maintaining your running endurance may be a challenge. There are many factors that contribute to them. Some are easily rectifiable and some are not. If you want to keep maintaining your running stamina and get better here are some running tips for you.

Madhusree Basu

Madhusree Basu

Author, Admin

Blogger and a fitness enthusiast. She loves running and Yoga and everything in between. She started running to manage her weight and to eat to her heart’s content. A true foodie at heart she shares whatever knowledge she has gained throughout the years about weight management and fitness.

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