Illness or overworking the body during exercise can sometimes leave us feeling weak in the knees — or more specifically, weak in our muscles. Simultaneous weakness and muscle tension can also occur in response to certain psychological states, including anxiety, according to updated 2024 research published in StatPearls. Anxiety is one way in which being in fight-or-flight mode manifests in the body. Impacting our physiological, cognitive, and behavioral functioning, anxiety is characterized by excessive worry about what is yet to come.
Anxiety-related muscle weakness may be isolated to one area of the body or may be felt all over (via anxietycentre.com). Larger areas of the body may be affected, such as the extremities, or areas as small as the toes or fingers. People often describe the experience differently. For some, it may feel as if their muscles have become heavy, rubbery, numb, shaky, or tense. Others describe their muscles as frail, limp, or unable to support their weight or physical movements. Muscle weakness associated with anxiety may be short-lived, lasting only a few seconds, or may linger for hours. Some individuals, however, experience chronic muscle weakness related to anxiety.
The body’s stress response has been triggered
If your anxiety prompts bouts of muscle weakness, it means the body’s stress response has been activated. This can cause weak muscles in a variety of different ways. For example, when in fight-or-flight mode, our blood pressure spikes, our muscles contract, and blood gets rerouted to the organs most essential for responding to danger (via AnxietyCentre.com). As a result, this can cause feelings of muscle weakness.
If you’re someone who starts to hyperventilate when anxious, this could also be the reason your muscles feel heavy due to the drop of CO2 in your blood that occurs when your breathing accelerates. Our blood sugar can also drop if anxiety is experienced on an ongoing basis. In the long run, lightheadedness, fatigue, and muscle weakness may set in. Alternatively, because anxiety can put us in a heightened state of worry and awareness, we may be more likely to think we’re experiencing muscle weakness even in the absence of a clear cause.
Muscle weakness may increase our risk of anxiety
Studies have shown that an opposite relationship between anxiety and muscle weakness may also exist. While anxiety may stimulate symptoms of muscle weakness, having weaker muscles may also increase one’s risk for anxiety, according to findings of a 2024 study published in the Journal of Cachexia, Sarcopenia and Muscle. Researchers tracked the handgrip strength and incident rates of anxiety and depression among 162,167 U.K. adults over an average 10-year follow-up period. The researchers found a connection between lower handgrip strength and a greater likelihood of developing depression and anxiety. Specifically, participants were at a 12% higher risk of developing anxiety per every 5-kilogram reduction in handgrip strength. Muscle weakness was also associated with a greater chance of depression and anxiety.
Managing muscle weakness related to anxiety will depend on the cause. Generally speaking, however, self-soothing practices can be helpful. This may include steadying your breathing, implementing grounding exercises, and eating some food to help regulate blood sugar levels. If anxiety is affecting your day-to-day functioning, reach out to your doctor or a mental health specialist for support.
