A device for governing strap length in a suspension trainer, the device comprising: a strap having proximal end and a distal end; a housing having an anchor means arranged to be attached to a support at an anchor point, the housing forming a cavity arranged to receive a proximal portion of the strap, the strap extending through an aperture in the housing exposing the distal end of the strap; a reel rotatably mounted in the housing and having the proximal end of the strap attached thereto, the reel being arranged to rotate about an axis; an engaging means formed in the reel or fixed to the reel, and corotating about the axis of rotation of the reel, the engaging means having a plurality of radially extending, axially spaced apart teeth; a return mechanism mounted on the housing to bias the reel in a first rotational direction about the axis to wind the strap onto the reel; and a locking means (204, 206) movable between a locked position preventing the reel from rotation and an unlocked position allowing the reel to rotate in the first rotational direction or a second rotational direction opposite to the first rotational direction depending upon a longitudinal force applied to the distal end of the strap; wherein the locking means comprises a rocker button arranged to pivot between the locked position and the unlocked position, the rocker button having: i) a lobe arranged to engage at least one of the teeth in the locked position; and ii) a lobe wall arranged to support the lobe without interfering with the rotation of the engaging means characterized in that the housing further comprises a tension pin and the distal portion of strap extending from the device passes over the tension pin before meeting the proximal portion of the strap remaining wound about the drum means such that the tension pin absorbs the force of the extended strap when under tension, preventing that force from being applied directly to the reel unit by the strap. a strap having proximal end and a distal end; a housing having an anchor means arranged to be attached to a support at an anchor point, the housing forming a cavity arranged to receive a proximal portion of the strap, the strap extending through an aperture in the housing exposing the distal end of the strap; a reel rotatably mounted in the housing and having the proximal end of the strap attached thereto, the reel being arranged to rotate about an axis; an engaging means formed in the reel or fixed to the reel, and corotating about the axis of rotation of the reel, the engaging means having a plurality of radially extending, axially spaced apart teeth; a return mechanism mounted on the housing to bias the reel in a first rotational direction about the axis to wind the strap onto the reel; and a locking means (204, 206) movable between a locked position preventing the reel from rotation and an unlocked position allowing the reel to rotate in the first rotational direction or a second rotational direction opposite to the first rotational direction depending upon a longitudinal force applied to the distal end of the strap; wherein the locking means comprises a rocker button arranged to pivot between the locked position and the unlocked position, the rocker button having: i) a lobe arranged to engage at least one of the teeth in the locked position; and ii) a lobe wall arranged to support the lobe without interfering with the rotation of the engaging means characterized in that the housing further comprises a tension pin and the distal portion of strap extending from the device passes over the tension pin before meeting the proximal portion of the strap remaining wound about the drum means such that the tension pin absorbs the force of the extended strap when under tension, preventing that force from being applied directly to the reel unit by the strap. i) a lobe arranged to engage at least one of the teeth in the locked position; and ii) a lobe wall arranged to support the lobe without interfering with the rotation of the engaging means characterized in that the housing further comprises a tension pin and the distal portion of strap extending from the device passes over the tension pin before meeting the proximal portion of the strap remaining wound about the drum means such that the tension pin absorbs the force of the extended strap when under tension, preventing that force from being applied directly to the reel unit by the strap.