Is EMS Fitness So Magical

"The muscles are constantly exerting strength, but the muscle length has not changed. The muscles are constantly contracting, but they have not further shortened or become longer, just like the state in which Captain America has been pulling the plane.".
The continuous electrical signal causes the isometric contraction of most of the muscles under the electrode piece, which is continuously contracting, and may be a muscle that you do not often recruit on your own, leading to muscle fatigue and subsequent soreness.
Perspectively, sweating is due to the constant activity of muscles that generate a large amount of heat, resulting in a continuous increase in skin temperature, which is related to the equipment worn (non heat dissipation of the electrode sheet and thicker and heavier equipment).
If the current is too large, it can cause the muscles under the electrode to stiffen instantaneously, just like a full body electric shock.
In fact, everyone has experienced muscle "cramps" (muscle spasms), where neurons in the muscle tissue spontaneously discharge, and the muscle after the spasm is also relatively sore and tired.
If you have some medical knowledge, it is known that a patient with epilepsy (epilepsy) who has a single onset can lead to general weakness and weakness.
Epilepsy occurs because of irregular electrical discharges in the brain, leading to loss of control throughout the body, limb twitches, and muscle stiffness.