Abstract: A bicycle-mounted exercising device includes a mounting assembly attachable to a bicycle frame, an elongated swingarm having an inner end and an outer end for coupling to a flexible elastic strap attachable to a dog's collar, a pivot assembly connecting the inner end of the swingarm to the mounting assembly for pivotal movement of the swingarm relative to the bicycle about a generally vertical axis defined by the pivot assembly, and a mounting attachment connected to the mounting assembly for pivotal movement about the vertical axis and, in turn, supporting the swingarm closer to its inner end than to its outer end for pivotal movement about a generally horizontal axis. The pivot assembly includes a spring which engages and biases the inner end of the swingarm in a downward direction and thereby biases the outer end thereof in an upward direction.