Kinesthesis, literally “feeling of movement,” is the sense that provides the brain with information concerning the contracting and stretching of our muscles. This information enables us to control our movements.Kinesthetic receptors are located in three different places. Cells in the muscles respond to stretching movements; cells in the tendons are sensitive to muscular contraction; and cells in the lining of the joints report changes in the position and movement of our limbs. Studies of abnormal functioning suggest that our basic kinesthetic cues stem from the joints.Many people have never heard of this sense, yet it is indispensable for survival, since kinesthetic impulses provide an automatic system for maintaining posture, walking, talking, gesturing, and performing any motor activity. If this system is seriously disrupted, as in tabes dorsalis, an advanced stage of syphilis, speech is usually slurred, facial movements are unco-ordinated, and the patient walks with a stumbling gait (locomotor ataxia).Kinesthetic cues are also responsible for our ability to distinguish light from heavy objects, to feel that the sidewalk is rough or slippery, and to walk the stairs in total darkness. All active sports and physical work are dependent on our muscle sense since it lets us know how far we are reaching, bending, or stretching. We become so completely adapted to these responses that we realize they exist only when they are absent—for example, when our foot falls asleep and gives no clue to its position. We are equally unaware of the hundreds of muscular reactions that occur every minute during speech. Some speech defects, such as nasality and lisping, are corrected by first analyzing the imperfectly formed sounds and then changing the movements that produce them. A similar technique is sometimes used in overcoming a foreign accent.Many occupations require great kinesthetic sensitivity. Dentists, pianists, surgeons, watchmakers, jugglers, and acrobats must all possess a highly developed muscle sense. Psychologists have therefore constructed a number of tests of co-ordination and control for use in vocational guidance. See APTITUDE TESTS (SPECIAL).