Abstract: An inversion exerciser includes a foot retaining device having a beam attached to a base to secure feet of user to the base, and having two fixed foot supports, a housing secured to the beam, a curved rack secured in the housing and having a number of teeth. A lever has one end rotatably attached to the housing and includes two movable foot supports movable toward and away from the fixed foot supports of the beam. A pawl is pivotally secured in the lever, and rotatable to engage with the teeth of the rack, and to selectively lock the lever to the beam, and a controlling device may control the pawl to engage with and to be disengaged from the teeth of the rack. A safety lock device is pivotally secured in the lever, and includes a tongue to selectively engage with the teeth of the rack and to selectively lock the lever to the beam by gravity force.