An exercise device is provided to couple a user's limb to a resistance mechanism and to tighten on the user's limb by a force applied in opposition to the resistance mechanism. The device may include a strap including a first portion, a second portion, and a third portion. The strap may define an adjustable opening configured to receive the user's limb. The first portion and the third portion of the strap may be attached to a closed loop shape configured for coupling to the resistance mechanism. A fixed opening may be coupled to the strap, and the adjustable opening of the strap may be formed by passing the second portion of the strap through the fixed opening. The device may also include a flexible material coupled to the strap and defining a tube providing the fixed opening.