Abstract: A foot restraining device for use during sit-up exercises. A rectangular platform which is tilted downward at a predetermined angle from its rear edge to its front edge is provided at its front edge with upwardly projecting, spaced apart jaws designed to straddle the bottom edge of a room door. A strap is used to bind the user's foot to the platform so that as he performs a sit-up, his foot is prevented from rising upwardly.