Muscle fatigue is a common sensation to experience after a hard workout or resistance training session, but when it persists, this may indicate a sign of an underlying condition or issue with your training regimen. Whether you’re a hardcore athlete or just starting off on your fitness journey, it’s important to understand elements of exercise science, both to enhance your performance and to prevent unwanted injuries. 

At QuickHIT Fitness Labs, we understand the science behind exercise and how your training method factors into common conditions like muscle fatigue. In this article, we’ll take a look at the different causes of muscle fatigue, how to identify them, and how to treat them effectively. For more information on resistance training, nutrition, and more fitness topics, please contact one of our locations in Wisconsin today!


Simply put, muscle fatigue is a phenomenon in which the muscles of the body can no longer continue to work or carry out a given physical activity. It may be caused by intense exertion during a workout, but it can also be related to underlying physiological conditions. Symptoms of muscle fatigue may include one or more of the following:

  • Pain in a specific area or muscle group
  • Soreness
  • Dizziness 
  • Difficulty catching your breath
  • Muscle twitching or trembling
  • Shakiness 
  • “Knots” or cramps

Most often, muscle fatigue is a temporary sensation caused by the buildup of acids in muscle fibers, which produces a feeling of soreness. However, muscle fatigue can become a chronic condition that either seems to persist or rarely goes away for long periods of time. It can also be caused by inherited diseases or autoimmune conditions. Regardless of the duration of muscle fatigue, knowing and understanding its potential causes can help you identify whether your soreness and weakness is due to a workout well done or a factor that warrants closer inspection.


DOMS is one of the most common causes of muscle fatigue, and it generally goes away within a matter of days. When you’re exercising or using considerable amounts of muscular energy, as one might during a long run or a resistance workout, your muscles produce a chemical called lactic acid. This is a byproduct that the body naturally makes whenever a muscle repeatedly contracts and consumes the energy stored in its fibers. Lactic acid produces a burning sensation that we commonly associate with intense physical exertion. It is this discomfort that tells us to give our body a break from the current activity or exercise we’re performing. In the hours and days after this secretion of lactic acid, the affected muscles begin to feel tight, tender, and weakened. This is the form of muscle fatigue known as delayed onset muscle soreness, or DOMS.

To treat DOMS, the most effective things you can do are to give your body adequate recovery time and to replenish its glycogen (energy) reserves with nutrients from a balanced diet. Most of the time, DOMS is nothing to be concerned about and will go away within a few days. The only thing that can cause this kind of muscle fatigue to persist is a failure to give your body adequate rest before jumping into another strenuous activity.


There are a wide variety of chronic conditions and diseases that may produce muscle fatigue or share overlapping symptoms with it. Some of these related conditions may include autoimmune diseases like hypothyroidism or fibromyalgia, as well as cancer, diabetes, anemia, and disorders of the central nervous system. While there is not enough time to exhaustively cover all of these persistent diseases, there is a lot to be learned from even a cursory glance at their relationship to muscle fatigue.

Chronic conditions usually impact the body in ways that compromise its natural functions, many of which can reduce one’s ability to recover from muscular exertion and fatigue. Heart failure, for instance, reduces cardiovascular function and circulation, so it can take more time to recover from exercise or physical strain. In a similar way, diabetes can slow the flow of blood to one’s muscles and joints, thereby intensifying the experience of pain and lactic acid buildup. Many autoimmune conditions can resemble the aforementioned symptoms of muscle fatigue. On the more extreme end, persistent conditions like kidney disease and liver disease actually lessen the body’s ability to remove waste products and toxins, including lactic acid. 

In the vast majority of instances, muscle soreness after a workout is no reason to panic or fear that the discomfort is permanent. That being said, every individual should consult their doctor about chronic muscle fatigue if it is not clearly connected to DOMS or a previously diagnosed condition. If left unaddressed or undiagnosed, muscle fatigue and soreness can be extremely harmful and even fatal, so be sure to have regular medical checkups and listen to your body when it tries to communicate with you!


The way we live on a day-to-day basis can have considerable influence on muscle fatigue. People with a sedentary desk job or high stress levels may be less active and feel fatigued more easily, just as athletes with a demanding workout regimen may experience muscle weakness from overtraining. A healthy diet plays a major role in nutrient absorption and healing, so take note of your eating habits. Elevated stress levels or inadequate sleep cycles can delay recovery processes for even longer periods of time. To determine potential causes of muscle fatigue, one of the first steps you can take is assessing your lifestyle habits. 


No two individuals are alike, and everyone will experience muscle fatigue in different forms and to varying degrees of intensity. If you suspect that you are enduring persistent or unwanted soreness, weakness, or other signs of exhaustion, it’s important to determine the cause as soon as possible. The best way to prevent muscle fatigue, which is a natural process, from developing into something more serious is by establishing healthy, proactive habits in advance. 

At QuickHIT Fitness Labs, we help our clients develop resistance exercise and nutrition regimens that suit their lifestyle and prevent the worsening of existing or potential health problems. To learn more about how resistance training and our scientifically backed programs can enhance your wellness, please contact one of our fitness labs in Wisconsin today!