Many different types of exercise device have been implemented in the prior art. Such devices operate to simulate various athletic activities such as rowing, cross-country skiing, stair climbing and the like. One particular class of exercise devices which have been found to have significant benefit comprise those devices which simulate a natural combined running and stepping action wherein a user's foot follows a path of resistance having both horizontal and vertical components. One notable class of such devices comprise those known as elliptical devices, as typified by the device disclosed in U.S. Pat. No. 5,383,829.
While exercise devices which simulate a running and stepping foot motion are in very widespread use, many such devices provide a single, fixed, foot path. In some instances, a user of the device may wish to modify the foot action to accommodate a longer or shorter stride length and/or vary the vertical component of the foot motion. Such modifications may be accomplished by changing the geometric configuration of the linkages constituting the device. However, such modifications cannot easily be accomplished when the device is in use; therefore, such systems cannot allow for in-motion modification of the foot path as is desired by many users. The prior art has implemented a great number of systems which attempt to modify the foot action of an elliptical trainer or other such running/stepping exercise device. Some of these prior art approaches are disclosed in U.S. Pat. Nos. 7,244,218; 7,201,705; 7,172,531; 7,316,632; 7,179,201; 7,169,089; and 7,214,168; as well as in pending published applications US 2007/0087907 and US 2007/0087906.
However, to date, there is still a need for a running/stepping type exercise device in which the horizontal and vertical components of the foot motion may be continuously modified while the device is in use. Any such systems should be relatively simple in construction, low in cost and easy to use. As will be explained in detail hereinbelow, the present invention provides a running/stepping exercise device, including elliptical devices, in which a user's foot path may be varied while the device is in use. The system of the present invention is simple, easy to use and easy to implement. These and other advantages will be apparent from the drawings, discussion and description which follow.