Langer Name Meaning. German, Dutch, Danish, and Jewish (Ashkenazic): nickname for a tall man, from an inflected form of Lang. According to Gottschald, in the Franconian dialect of German this was also a term for an unskilled laborer (more fully, Handlanger).
Muscle does not weigh more than fat, any more than lead weighs more than feathers. A pound is a pound is a pound. Where the misunderstanding often comes in is that muscle is much more dense than fat, so that, by volume, it seems to weigh more. That is, a pound of muscle occupies less space than a pound of fat. In addition, because a pound of muscle burns more fat than a pound of fat, even at rest, by increasing your lean muscle tissue mass, you're helping your body burn more calories. But back to your question.
Where the lumbar spine, hips and tops of the legs come together is a very important articulation in the body that enables us to stand, walk, run and play. If there is a weakness or dysfunction in this area, then other muscles (like those of the lower back) work harder to splint the area and keep it stable. This is why so many people experience a tight lower back; the lumbar erector muscles have to work twice as hard to make up for weaknesses elsewhere in the body (e.g., the glutes). By simultaneously strengthening muscles surrounding the lower back and stretching others, the lumbar spine muscles can be taught to release and thereby reduce excessive lumbar lordosis. The dome shape of the BT makes it perfect for performing exercises for the lumbar spine while lying in a prone position.