What Causes Muscle Fatigue?

What Causes Muscle Fatigue?

Your muscles are at their strongest and most resilient when you begin a workout. However, over time and after continued exercise, your muscles may start to weaken. You may experience a dull aching of the muscles or lack the energy to continue exercising or perform everyday tasks. This is known as muscle fatigue. 

Fatigue starts in the central nervous system (CNS). Muscle fatigue is a common symptom of exercise that negatively impacts your muscles’ ability to perform at their maximum ability. This is often the result of heavy or intense workouts, as the force behind your muscle’s movement decreases, causing you to feel increasingly weaker throughout exercise.

Muscle fatigue is normal and commonly indicates that you push your body in a healthy, constructive way. After all, the stress you put on your muscles is what ultimately leads to growth. However, muscle fatigue can also be an indication of overtraining or the result of some health conditions.

Muscle Fatigue Symptoms

Muscle fatigue can occur in any muscle in the body, especially if you overwork muscles. Suppose you are new to working out, trying out a different exercise, lifting with heavier weights, or exercising for longer than normal. In that case, you may be more susceptible to the following symptoms of muscle fatigue:

  • Muscle Weakness
  • Sore muscles
  • Localized pain
  • Viral infections
  • Shortness of breath
  • Poor sleep
  • Lack of energy
  • Muscle twitching
  • Trembling
  • A weak grip
  • Muscle cramps

Muscle fatigue is a good indication that you should decrease the intensity of your exercise, lift lighter weights, or cease exercise altogether. If your muscles fatigue quickly or without exercise at all, you should seek medical attention.

Common Causes of Muscle Fatigue

In most cases, muscle fatigue is nothing to worry about. The purpose of the exercise is to put your body under stress to catalyze results. It is natural for the body to weaken throughout a workout in response to its stress. As long as you are not overtraining, muscle fatigue is normal and healthy.

That being said, there are other common and mendable, possible causes of muscle fatigue to consider:


Throughout a workout, your body loses water via sweat. Dehydration can cause energy levels to drop and muscles to cramp or weaken. It is important to replenish those fluids throughout exercise to prevent excessive dehydration.

Sweat also causes the body to lose important minerals such as potassium, magnesium, and sodium. Deficiencies in these minerals can lead to further dehydration and decreased energy production and muscle efficiency.

It is important to hydrate before, during, and after workouts. In addition to water, replenish your fluids and minerals with an electrolytes-rich drink such as coconut water or a sports drink. Follow this easy guide to keep your body hydrated at all times:

  • Drink 17 to 20 ounces of water two to three hours before you start exercising.
  • Drink eight ounces of water 20 to 30 minutes before you start exercising or during your warm-up.
  • Drink 7 to 10 ounces of water every 10 to 20 minutes during exercise.
  • Drink eight ounces of water no more than 30 minutes after you exercise.

Lactic Acid Buildup

Lactic acid is produced in your red blood cells and muscles when your oxygen levels are low. This is often the case during intense exercise. As your body breaks down carbohydrates, lactic acid is created as a byproduct. 

Lactic acid buildup in the muscles can create soreness, tension, and reduced mobility. This makes it a common culprit for muscle fatigue.

As previously discussed, dehydration and a magnesium deficiency can contribute to lactic acid buildup. In order to replenish your fluids before, during, and after workouts, you can restore magnesium levels via Epsom salt baths.

Here are some other methods you can use to prevent lactic acid buildup:

  • Incorporate active recovery into your rest days
  • Practice breathing techniques
  • Warm-up and stretch before and after workouts
  • Drink orange juice

Physical Condition

The most common cause of muscle fatigue is a lack of physical conditioning. If they are not used regularly, muscles will become weaker over time as muscle fibers are partially replaced with fat. This can make it further difficult to finish workouts and maintain your physical condition. 

Both obesity and malnourishment can contribute to rapid and frequent muscle fatigue. In malnourished individuals, the body will extract energy from the muscles when the glycogen levels are depleted. This can also result in muscle weakness.

To prevent this, make an effort to maintain your diet and exercise. Be sure to eat complete meals of protein, carbs, and fat before and after working out. Also, incorporate both resistance training and cardio into your workouts.

For a quick and convenient workout that combines resistance training with high-intensity cardio, check out the Ski-Row Air or the Ski-Row Air + PWR by EnergyFit.

Medical Conditions that Cause Muscle Fatigue Symptoms

If your muscles fatigue quickly during exercise, or with little to no exercise at all, you may have a health condition. Consult your doctor if you are experiencing frequent muscle fatigue, as you may have one of the following conditions:

  • Addison’s disease
  • Anaerobic infections
  • Anemia
  • Anxiety
  • Botulism
  • Cerebral palsy
  • Chemotherapy
  • Chronic fatigue syndrome (CFS)
  • Depression
  • Diabetes
  • Fibromyalgia
  • Hepatitis C
  • Heart disease (specifically heart failure)
  • HIV
  • Hypothyroidism
  • Influenza (the flu)
  • Kidney disease
  • Liver disease
  • Mineral deficiency
  • Muscular dystrophy
  • Myasthenia gravis
  • Myositis (muscle inflammation)
  • Poor muscle tone due to a medical condition
  • Pregnancy
  • Sleep deprivation
  • Stroke
  • Tuberculosis

How to Prevent Muscle Fatigue

Besides remaining stretched and hydrated, there are several ways that you can prevent your muscles from quickly fatiguing during workouts.


Caffeine is a popular ingredient in many pre-workout supplements as it increases energy and stimulates fat burning. High amounts of caffeine doses have been shown to enhance performance during extended periods of exercise involving aerobics and resistance. On top of that, the effects of caffeine on short periods of intense aerobic activity have been reported to be significantly beneficial.

Natural Products

While caffeine is a synthetic product that some people might want to avoid, some natural products can also alleviate or prevent the symptoms of muscle fatigue.

Ginseng is an herb with several possible health benefits, including muscle fatigue relief. Research has shown that red ginseng can improve muscle performance in people during weight training.

Garlic is another natural product with the potential to prevent muscle fatigue. In that same study, it was shown that garlic could increase the endurance of mice when running on treadmills and how fast they recover.

Nutritional Supplements

Several well-researched nutritional supplements can also prevent muscle fatigue. Always consult your doctor before taking any dietary supplements.

  • Multivitamins are an efficient and holistic way to address dietary deficiencies. Many multivitamins provide your complete daily value of key vitamins and minerals. 
    Depending on your deficiencies, you may want to take a more specific vitamin supplement. Vitamin D is a common deficiency and can be taken as a daily supplement.
  • Fish oil supplements contain omega-3 fatty acids. In addition to improving muscle performance, these healthy polyunsaturated fats may benefit brain function, cardiovascular health, immune function, and bone health.
  • Creatine is one of the most popular and well-researched supplements on the market. It has been shown to increase muscle mass and strength while reducing fatigue.

Breaking it All Down

Working out puts stress on your muscles, and that stress can lead to fatigue. This is a good thing, though, as fatigued muscles mean muscle fibers are breaking down and growing stronger. However, to maximize the intensity of your workouts, you may want to prevent muscle fatigue as much as possible.

It is important to remain well hydrated before, during, and after workouts. Sports drinks and coconut water can help replenish electrolytes. Well-balanced meals throughout the day will also keep your muscles energized for a workout.

Supplements, such as caffeine and creatine, can keep your body pushing to the max. Many people may also find benefits in vitamin supplements, as vitamin deficiencies are common and treatable.

If you are experiencing muscle fatigue with little to no exercise, it may indicate a medical condition. Consult your doctor as soon as possible.

While muscle fatigue may be hard to push past, it is generally a sign that you’re getting healthy, meaningful exercise. Keep pushing to get the results you want!



Muscle fatigue: general understanding and treatment | NCBI

Lactic acid test | Medline Plus 

Orange juice improved lipid profile and blood lactate of overweight middle-aged women subjected to aerobic training | Maturitas 

Muscle fatigue: general understanding and treatment | NCBI 

Comparison of effects of yoga & physical exercise in athletes | NCBI 

American College of Sports Medicine position stand. Exercise and fluid replacement | NCBI

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