Embodiments of a user-adjustable resistance mechanism, and embodiments of an exercise apparatus employing such a user-adjustable resistance mechanism, are provided. In one embodiment, the exercise apparatus includes a support structure, a user-manipulated element movably coupled to the support structure and configured to be moved by a user during the performance of an exercise in opposition to an output resistance, and a user-adjustable resistance mechanism. The user-adjustable resistance mechanism includes, in turn, an input resistance assembly and a lever assembly comprising a first plurality of levers rotatably coupled in series between the user-manipulated element and the support structure. The input resistance assembly is configured to be selectively coupled by a user to the lever assembly at any one of a plurality of locations to determine the cumulative load arm length of the first plurality of levers and the output resistance opposing movement of the user-manipulated element.