A reinforcing assembly for air ducts includes a helical reinforcement with an outer circumference and at least one connecting element for fixing a pitch of a helix formed by the helical reinforcement. The at least one connecting element may be fixed to the helical reinforcement by a plurality of j joints with mutually arranged spacing. The reinforcing assembly may be combined with an air duct to form a duct system for transmitting and distributing air that retains its shape regardless of the system's internal air pressure.