Exercise devices, and in particular weight training machines, typically include one or more mechanical members that the user repeatedly moves along a prescribed path for exercise. Conventionally, movement of the mechanical member is resisted in some fashion (often by weights) to render the movement more difficult and thereby intensify the exercise. The movement of the mechanical member determines what muscle or muscle groups are to be involved in the exercise.
One popular exercise movement for weight training is the “biceps curl” motion, in which an exerciser substantially straightens his arms at the elbow to grasp a handle or other grasping device, and bends (or “curls”) his arms while maintaining the upper arms or elbows in a substantially stationary position. This exercise movement tends to work the biceps brachii, biceps brachialis, and forearm flexors of the user.
Some biceps curl machines include a frame that has a base and vertical uprights that rise from the base, a seat that is mounted to the frame, and a pair of movement arms that are pivotally mounted to and extend inwardly from the vertical uprights. Support pads for the user's elbows extend inwardly from the vertical uprights. The user sits on the seat, rests his elbows on the supports, grasps the movement arms with his arms straight, and curls his arms such that the movement arms pivot relative to the frame. This movement is resisted by weights or other resistance system.
In many biceps extension machines of this general configuration, planes defined by each vertical upright are generally parallel with one another. The axes of rotation of the movement arms tend to be substantially normal to these planes. As a result, the movement arms are positioned in front of a seated user. This configuration may be inconvenient for a user as he enters the machine; often the movement arm must be moved out of the way in order for the user to sit. In addition, the parallel relationship of the axes of rotation may inhibit complete contraction of the biceps muscle.