An instrument for exercising the muscles of the mouth, comprising: a first body and a second body (1, 2), which are mobile with respect to one another so as to pass from a resting position to at least one operating position against the action of a counteracting elastic element (3) a first portion and a second portion of gripping (4,5) means (6) for adjusting the elastic pre-loading of said elastic element (3) means (7) for adjusting the distance at rest of the portions (4, 5).
