Muscle-building apparatus

A muscle-building apparatus for building the muscles of a user performing a physical exercise, the muscle-building apparatus comprising a treadmill which is displaceable in a longitudinal direction and in opposite senses, a force generator that supplies an adjustable pushing or dragging force, and a swiveling support mechanically coupled to the force generator for the user to perform a pushing or dragging exercise on the swiveling support, wherein the force generator comprises an inner annular cylinder, an outer concentric cylinder, wherein the opposite faces of the inner annular cylinder and the outer concentric cylinder comprise a plurality of first vertical ribs and a plurality of second vertical ribs uniformly distributed on the respective inner and outer surfaces of the inner annular cylinder and the outer concentric cylinder.