A regulating device for gymnastic machines and the like, includes at least a lever (2) for manual selective lock and release, associated with a first member (3), at least a toothed rod (4), associated with a second member (5) slidable relative to said first member (3), and a pawl (6) mechanically interlocked with the lever (2) and selectively engageable in one of the teeth (7) of the toothed rod (4) to block rigidly the second member (5) with respect to the first member (3) in any position by a user the lever (2) being selectively movable from at least a first position of sliding of the second member (5) relative to the first member (3), wherein said pawl (6) can be released from said toothed rod (4), to at least a second position of blocking said second member (5) relative to said first member (3), wherein the pawl (6) is rigidly engaged in one of the teeth (7) of the toothed rod (4), to at least a third position of substantial clearing of the mechanical backlashes between the second member (5) and the first member (3).