Stapedius muscle excess movement of the stapes, helping to control the amplitude of sound waves from the general external environment to the inner ear Paralysis of the stapedius allows wider oscillation of the stapes, resulting in heightened reaction of the auditory ossicles to sound vibration. This condition, known as hyperacusis, causes normal sounds to be perceived as very loud. Paralysis of the stapedius muscle may result when the nerve to the stapedius, a branch of the facial nerve, is damaged, or when the facial nerve itself is damaged before the nerve to stapedius branches. In cases of Bell's palsy, a unilateral paralysis
In vitro muscle testing the level which ensures maximal motor unit recruitment. The servomotor can be programmed to maintain a given force while allowing the muscle to change length, vice versa, or the muscle may be subject to more complex testing, such as in work loops. When pennate muscles are used, sonomicrometry is often used to accurately determine fiber length during the test. "In vitro" muscle testing can be done on any scale of muscle organization - entire groups of muscles (provided they share a common insertion or origin, as in the human quadriceps), a single muscle, a "bundle" of muscle fibers, a single