Harvard Mental Health Letter

In Brief: The mystery of muscle relaxation

In Brief

The mystery of muscle relaxation

Muscle relaxation, sometimes enhanced by biofeedback, is often used in the treatment of anxiety and insomnia on the assumption that patients can calm their minds by learning how to relax their bodies. A 2007 article challenges this assumption and raises questions about how this therapy actually works.

The standard theory is that muscle relaxation relieves anxiety by bringing about a physical state that opposes the emergency fight-or-flight response. When muscles are relaxed, heart rate, blood pressure, and stress hormone levels are lowered, and changes in emotions and thinking follow.

Muscle tension is measured with electromyography (EMG), which involves either placing electrodes on the skin (convenient but not highly accurate) or inserting a needle into muscle tissue (more accurate, but uncomfortable). Electrical activity in a muscle is higher when it is contracted, or tense, and lower when it is relaxed or inactive. In biofeedback therapy, patients use EMG recordings as a guide in training themselves to relax.

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