Apparatus for exercising the abdominal muscles includes a flexible substrate that substantially conforms to a user's abdomen, with a tacky pressure-sensitive adhesive disposed on one side of the flat or contoured surface, for adhering the exercise apparatus to the user's abdomen, and a system for attaching additional weight to the apparatus for providing increased resistance. The pressure sensitive adhesive (PSA) allows the exercise apparatus to adhere to the user's abdomen, and enables releasable attachment, such that the apparatus can be attached and detached from the abdomen repeatedly, and can be reused. Optional weights are attached to the apparatus to increase resistance, as desired. While on his/her hands and knees, the user contracts the stomach muscles and pulls his/her abdomen with the attached apparatus inward toward the spine, thus exercising the abdominal muscles.