Recently, using public sport equipment has been propagated in my country. A novel outdoor exercise equipment was designed and developed in order to use in parks. It is a link segment structure that trains abdominal muscles. To find the optimal length of the links and avoid injuries, a detailed musculoskeletal model of human was developed combined with the equipment model. The simplest design, modeling a close chain dynamic system and create spine contact with the device in model were some of the challenges facing the project. This Video shows a prototype of the device.