Feeling tired after running a hard workout, long run, or race is expected. Running is a physically demanding form of exercise, so nearly every runner feels fatigued after running at one point or another during their training plan.
But what happens when fatigue from running lingers after the finish line? What if you’re chronically exhausted and cannot perform your day-to-day tasks, let alone think about a hard running workout?
Numerous factors, such as nutrition, sleep, or overtraining syndrome, can contribute to feeling tired all the time and put a damper on your running and general wellness.
Finding out the specific cause of your fatigue is the first step in helping you return to your normal level of physical activity and feeling like yourself.
In this guide geared towards exhausted runners, we discuss why you might be tired all the time, the common causes of running fatigue, and when it may be time to take a break from running or any fitness training regimen.

Why Do I Feel Fatigued After Running?
Tiredness after running can simply be a sign that you pushed your body on the running track and had a good workout.
Still, if the fatigue does not resolve within a few hours after your workout—or worse, if it snowballs or accumulates from one workout to the next—it’s a sign that you need to troubleshoot your training, nutrition, and health to identify the cause of your exhaustion.
What Is Running Fatigue?
If you aren’t just tired after running but feel exhausted during your runs or throughout the day, it’s time to consider running fatigue.
Running fatigue essentially refers to physical exhaustion, sluggishness, low energy, and/or sleepiness during or after running, as opposed to just some muscle fatigue or tired legs after a tough session.
Exhausted runners typically recount that their running fatigue began as feeling tired after intense workouts or longer runs.
While initially, this fatigue resolved after refueling and a good night’s rest, eventually, they began to feel chronically sluggish and fatigued without an appreciable resolution between workouts.
Some other common symptoms of chronic running fatigue can be persistent muscle soreness, an elevated resting heart rate, a performance dip or plateau, frequent illness, or a loss of motivation to run.
Running fatigue can adversely affect running performance because when you are running tired, exhaustion can impact your energy, strength, speed, power, and stamina.
It can also permeate into other aspects of your life, impacting work, activities of daily living, appetite, sleep, and mood.

What Are The Most Common Causes of Running Fatigue?
Most of the time, with just a little bit of detective work and introspection, you can identify the cause of your running fatigue and why you feel like a tired runner.
Keep reading for some of the most common causes of running fatigue:
#1: Overtraining
Whether you are half marathon or marathon training as an experienced runner or just starting out with some easy runs, overtraining can be a possible cause of your fatigue.
Your training load is often to blame when it comes to feeling exhausted after running or sluggish while running.
Overtraining is one of the most common causes of running fatigue and can occur in beginners to elites. Overtraining can occur when you do too much too soon, increase your mileage or intensity too quickly, or don’t focus enough on the recovery process after your runs.
Overtraining syndrome refers to a condition marked by the presence of cruising physical and mental symptoms, such as sluggishness, low energy, appetite changes, hormonal imbalances, difficulty sleeping, irritability or other mood changes, compromised immunity, reduced athletic performance, and ultimately, burnout.

Interestingly, overtraining syndrome isn’t necessarily brought on solely by running high mileage or running too hard and fast.
Rather, overtraining syndrome occurs when the volume and intensity of training exceed what the body can handle in the context of all the other stressors and factors in one’s life.
For example, you might be able to handle higher peak mileage and more intense speed workouts without suffering overtraining syndrome when you prioritize recovery, get plenty of sleep, and have your nutrition and hydration dialed in.
In contrast, you could deal with running fatigue and overtraining at lower training volumes when your life is very hectic and exhausting, such as while moving, starting a new job, or taking care of an ailing family member.
Your body only has a certain stress tolerance, and running is only one of the factors that contributes to your overall stress.
Ensure your training plan is appropriate for your physical fitness, experience, and stress level.

#2: Anemia and Low Iron
Another common cause of running fatigue or low energy in long-distance running is anemia or low iron levels.
Iron deficiency is particularly common among vegan and vegetarian runners as well as female runners who menstruate. Plant-based diets are devoid of heme iron, the more absorbable and bioavailable form of dietary iron, which is found in animal proteins.
Vegans and vegetarians who eat plant-based foods such as spinach and lentils get iron in their diet, but this iron is non-heme iron, which is more poorly absorbed by the body. As a result, runners who don’t eat meat are at an increased risk of iron-deficiency anemia.
It’s important to note that plant-based diets can be completely healthy for runners and don’t necessarily lead to iron deficiency, so long as the diet is balanced and provides all of the essential nutrients in adequate amounts to support running and overall health.
Studies show1Nebl, J., Haufe, S., Eigendorf, J., Wasserfurth, P., Tegtbur, U., & Hahn, A. (2019). Exercise capacity of vegan, lacto-ovo-vegetarian and omnivorous recreational runners. Journal of the International Society of Sports Nutrition, 16(1). https://doi.org/10.1186/s12970-019-0289-4 that exercise capacity is not adversely affected by a vegan diet or other plant-based diet so long as total caloric intake is sufficient.
Female runners who menstruate are also at an increased risk of anemia due to the monthly bleeding and depletion and loss of red blood cells.

Long-distance runners and endurance athletes are already prone to low iron because running is associated with 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.
Anemia and low iron in runners can cause sluggishness, shortness of breath, general fatigue, pallor, and dizziness, among other symptoms.
Runners with anemia will have low hemoglobin and hematocrit, indices of your red blood cell count.
Runners with iron deficiency will have low ferritin and higher total iron binding capacity levels. Ferritin is a measure of your stored iron, so low ferritin means your iron reserves are lacking.
When your total iron binding capacity is high, you have extra availability to bind more iron, again meaning you don’t have a lot of iron trying to bind to hemoglobin molecules.
Ferritin should be greater than 30ng/ml for female runners and over 40ng/ml for male runners.

#3: Dietary or Nutritional Deficiencies
The foods you eat provide the calories and nutrients your body needs to perform optimally, both in terms of when you run and during everyday life.
Running fatigue can be brought on by a diet deficient in total energy or certain nutrients.
If you’re not consuming enough calories, your body won’t have the energy it needs to run well, recover from your workouts, and maintain your health and vigor.
Runners who don’t eat enough carbohydrates or protein can also deal with chronic fatigue, as carbs provide energy for vigorous exercise and protein is necessary to rebuild and repair cells and tissues after exercise.
Longer distances deplete glycogen stores, so if you consume enough carbohydrates during your run and replace glycogen stores by refueling with carbohydrates after your run, your body will not have adequate fuel for energy production during your next workout.
According to the American College of Sports Medicine (ACSM), it is ideal to ingest 30-60 grams of carbohydrates per hour during endurance exercise2.American College of Sports Medicine. (2009). Nutrition and Athletic Performance. Medicine & Science in Sports & Exercise, 41(3), 709-731. https://doi.org/10.1249/mss.0b013e31890eb86
This equates to 120-240 calories of carbohydrates per hour. These carbohydrates can come from sports beverages, energy gels or chews, or foods such as dried fruit, pretzels, bananas, or honey packets.
The standard recommendation3ACSM Certification Blog and Articles. (n.d.). ACSM_CMS. https://www.acsm.org/all-blog-posts/certification-blog/acsm-certified-blog/2021/01/25/nutrient-ratios-for-strength-training for carbohydrate refueling post-run is to consume 0.6-1.0 g/kg of carbohydrates within 30 min and again every 2 hours for the next 4-6 hours.
In terms of protein, the American College of Sports Medicine recommends that athletes consume at least 1.2-2.0 grams of protein per kilogram of body weight per day. For example, a runner weighing 154 pounds (70 kg) should consume at least 84-140 grams of protein daily to meet their physiological needs.
Additionally, micronutrients like vitamin B12, vitamin B6, vitamin C, and iron are needed for energy metabolism, cell turnover, oxygen transport, and nerve function.

#4: Dehydration
Failing to ingest enough water or other fluids with electrolytes can cause both acute and chronic fatigue in runners.
You should aim to consume around 64 ounces of water per day, or enough fluid so that your urine is pale yellow. Drinking water consistently throughout the day will help keep you well-hydrated.
#5: Inadequate Sleep
Runners usually need between 7-9 hours of quality sleep per night.
If you’re not getting enough sleep regularly, your recovery from workouts will be hampered, and you’ll deal with sluggishness while running, fatigue after running, and general exhaustion during the day.
#6: Certain Medications
Some medications used to treat common medical conditions can cause fatigue. For example, antidepressants, such as Prozac and Zoloft, may cause low energy, and many anti-anxiety medications, such as Klonopin, Xanax, and Ativan, can cause drowsiness.
Antihistamines like Benadryl can cause sleepiness, and beta blockers used to treat hypertension can make you feel tired while running.

#7: Medical Conditions
There are several medical conditions that can cause chronic fatigue while running or exhaustion after running, such as chronic fatigue syndrome, Lyme disease, diabetes or insulin resistance, the Epstein-Barr virus, the herpes virus, and other infectious diseases.
Consult your physician if you have concerns about any of these conditions.
What Can You Do To Lessen The Impact Of Fatigue On Performance And Running Injury Risk?
When you have acute fatigue after a speed workout, long run, or intense workout, optimizing your recovery is important to help shake that exhausted runner feeling.
Tips to support recovery from hard runs include:
- Cool down and stretch after the workout.
- Refuel within 30 minutes after the run with several hundred calories in a carbohydrate-to-protein ratio of 3:1 or 4:1.
- Get at least 7-9 hours of sleep at night and/or take a nap in the afternoon following your workout.
- Ensure the overall quality, composition, and energy intake of your diet is adequate to support your training.

When Should I Take a Break from Running?
If you’re doing all the right things to promote recovery from your workouts but you still feel tired 24 hours after running, take a rest day.
Exhausted runners dealing with more chronic running fatigue are advised to hang up their running shoes for a full two weeks to allow their bodies time to recover and reduce further injury risk.
If the running fatigue persists after this time off, it’s a good idea to consult your healthcare provider for further testing and investigation into the cause of your unresolved exhaustion.
If you think nutrition may be the culprit that makes you feel exhausted, check out our nutrition guide for runners:
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