Why does the arm lift automatically and uncontrollably?

This is the Consham phenomenon. Press the back of your hand against the door frame or wall for about 30 seconds, and then let your arm hang down naturally, at which point your arm will "float" uncontrollably, as if an external force is pulling it.

When standing with your arms downward, press the back of your hand against a wall or other fixture for 40-60 seconds, and then let your arm hang down naturally.

Phenomenal causes. If people hold their arms close to their body and inhibit this involuntary movement, the involuntary "lifting" signal is blocked by the brain before reaching the muscle. Although the differences between the two explanations may seem subtle, understanding the mechanisms behind the Konstam phenomenon will help to suppress other involuntary movements.

For example, Parkinson's disease.

or muscle twitching caused by Tourette's syndrome. Similarly, if you walk with a sandbag strapped, your muscles get used to the sensation after walking for dozens of minutes, and then you feel "lighter" after you take off the sandbag.

The Constance phenomenon is an involuntary movement phenomenon in which you press the back of your hand against a door frame or wall for about 30 seconds, and then let your arm hang down naturally, and you will notice that your arm is raised uncontrollably. Similarly, if you walk with a sandbag strapped, your muscles get used to the sensation after walking for dozens of minutes, and then you feel "lighter" after you take off the sandbag.

If people hold their arms close to their body and inhibit this involuntary movement, the involuntary "lifting" signal is blocked by the brain before reaching the muscle. Although the differences between the two explanations may seem subtle, understanding the mechanisms behind the Constance phenomenon will help people suppress other involuntary movements, such as tremors caused by Parkinson's disease or muscle tics caused by Tourette's syndrome.

When completely relaxed, the motor cortex in the brain is in a resting state and does not give active exercise instructions to the muscles. At this point, another string of control signals is externalized and embodied by the movement of the limbs, and the Konstam phenomenon is born. In fact, the signals emitted by the motor cortex of the brain are modulated by the basal ganglia and the lower nerve nuclei before they are transmitted to the target muscle groups.

When our brain's motor cortex sends out movement signals, the content of its signals is not a specific muscle control assembly, but a more advanced and abstract signal, such as controlling the movement of the limbs to a certain direction. When this higher signal is transmitted to the basal ganglia and lower nuclei, it is translated as a muscle group control signal and transmitted to the cerebral cortex through a feedback mechanism for precise control.