The stiffening, then relaxing of their muscles is involuntary and usually occurs when the animal is startled or sometimes when they step over an object.
The condition lasts only a few seconds and produces no pain to the animal. They are fully conscious during the brief episode, so the term fainter or fainting goat is a misnomer.
It is the stiffening and relaxing which builds the muscles to unusual proportions and very tender meat. I’m reminded of the almost ancient commercials of body builder, Charles Atlas. His method of tightening and relaxing muscles in body building was called “dynamic tension”.
With myotonic goats, the exercise is strictly involuntary!