Many people struggle with muscle fatigue. Sometimes muscle fatigue is caused by an illness, such as chronic fatigue syndrome or fibromyalgia. Often, muscle fatigue is the result of “deconditioning” (also known as couch potato syndrome), which involves diminished muscle strength due to inactivity. In rare cases, muscle fatigue results from exposure to toxins or certain medications.
The most common cause of muscle fatigue, where no injury exists, is anemia.
Anemia and muscle fatigue
Anemia is an illness which results in fewer red blood cells. Because you require substantial reserves of hemoglobin in order to circulate oxygen throughout your body, anemia causes a shortage of oxygen, resulting in muscle fatigue, cognitive problems, and severe exhaustion.
When your muscles don’t get enough oxygen, they can’t perform to their full potential and are more susceptible to injuries and achiness associated with muscle fatigue.
Anaerobic metabolism
Another reason for muscle fatigue with anemia involves anaerobic metabolism, or energy produced without utilizing oxygen. Whenever you require maximum energy for high-intensity sports, such as sprinting, your lungs depend on ample supplies of oxygen. Once you reach your anaerobic threshold, where your lungs are unable to produce sufficient oxygen, your body instantly starts converting energy from non-aerobic sources, such as stored carbohydrates. The result is muscle fatigue.
Let’s say you’re walking slowly to a bus stop, and you suddenly notice your bus starting to pull away from the curb. You spring into action, running hard to catch the bus. By the time you catch your breath, you may feel tired, flushed, sweaty, and a little bit shaky. That’s the result of healthy anaerobic metabolism, your body trying to get more oxygen-carrying red blood cells to your muscles, but instead having to dip into your stores of adenosine triphosphate (ATP) for energy. An unfortunate side effect is muscle fatigue caused by production of lactic acid.
With anemia, a severe shortage of oxygen interferes with anaerobic metabolism, creating a constant “oxygen debt.” This results in a buildup of lactic acid, which in turn causes chronic muscle fatigue pain.
And while healthy individuals may experience muscle fatigue after swimming a few qui k laps around the pool, anemia sufferers feel long-lasting muscle pain from minimal physical exertion.
Diagnosing anemia with muscle fatigue
Your doctor may run a few blood tests to determine if anemia is the cause of muscle fatigue. The most common form of anemia is pernicious anemia, a cause of vitamin B12 deficiency. Iron deficiency is also a common cause of muscle fatigue, as well.
To treat muscle fatigue from pernicious anemia, your doctor may prescribe non-edible vitamin B12 as an injection or sublingual supplement. Other forms of over-the-counter (OTC) vitamin B12 are also available to get your vitamin levels back to normal.