A lower body exercise device for use with a seat. Other embodiments of the seat mountable lower body exercise device include a lower body exercise mechanism (20) for simultaneous use by a user while working, reading or doing other sedentary activities, and a simple installation mechanism (10) for various forms of seat. In addition, simple detachable function (11a), (11c), and multiple adjustment functions (21aa), (23), (30) for various user's circumstances is available, and one or more exercise alteration is also available by adjustment (30), (33a), (27c), (24b). Other embodiments include a magnetic cycle system which may reduce the exercise device body (21'') in size.