Muscle fatigue is a condition where your muscles lose ability to generate force. It can be a sign that your body needs a break, or a symptom of serious illness. It’s important to be able to recognize muscle fatigue, and to be able to differentiate it from the regular “burn” associated with working out. Doing so will allow you to spot early warning signs of underlying medical issues, understand how to challenge yourself physically without going too far, and avoid injury.
Signs and Symptoms
Sudden and or severe sensations of muscle weakness are a key indicator of muscle fatigue. Your legs may feel like “jelly”–wobbly and unable to support your weight.
Involuntary muscle twitches in the legs is another common sign of muscle fatigue. This is particularly common in people diagnosed with fibromyalgia. The medical term for these twitches is myoclonic jerks.
If you are experiencing muscle fatigue, your grip may be weak. For example, you may find you are unable to hold your water bottle or sports equipment.
Vigorous, sustained exercise is often responsible for muscle fatigue. You may have been doing an activity too long, or doing too much without proper training. Either way, if you know or suspect you are experiencing muscle fatigue remember to take a break. Otherwise, you are at far greater risk for injury–in part because your nerves are already frazzled from sending you signals to quit, and you may not be as able to detect when you are moving in a way that’s especially harmful.
Nervous fatigue and metabolic fatigue may be involved in overexertion related muscle fatigue. Nervous fatigue occurs because the nerve that generates the signal for a given muscle to contract has been holding that signal too long, and at too high a frequency. In other words, though your muscles could potentially do more with training, the nerve isn’t yet able to keep signaling them on.
Metabolic fatigue means your muscles either don’t have enough “fuel” or have too much of the byproducts of that fuel building up and messing with the ability of the muscle to function properly. Eating well, regularly, and enough to support your weight and activity level will help lower your risk of metabolic fatigue.
Sometimes, muscular fatigue may be a symptom of neuromuscular disease. Neuromuscular diseases impact the ability of your muscles to function, and may be pathologies of the muscle or may be pathologies of the nerves and/or tissues surrounding the muscle.
If you’re struggling with muscle fatigue regularly, you should consult a sports medicine professional to identify to cause. They can help diagnose the issue, and use testing to identify an optimal workout for your body type so that your can get stronger the smart way.