Exercise device with natural gait motion and single synchronous control system

Abstract

An exercise machine with a more natural gait which, in some embodiments, further allows for a variable stride length while in use. In one configuration, each side of the exercise machine has a first crank assembly connected at an upper location on a pedal arm and a second crank connected at a middle location on the pedal arm, and a pedal is attached to a lower location of the pedal arm. The first crank assembly is connected to the pedal arm by a crank arm. The second crank assembly is connected to the pedal arm via a crank arm pivotally attached to a crank link. The path of each pedal is determined by the lengths of crank arms and crank links of the first and second crank assemblies rotating in synchronous motion.

What is claimed is: 
     
         1 . An exercise device comprising:
 a frame;   a first and a second crank system mounted opposing sides of the frame adapted for positioning a user therebetween, each of the first and second crank system comprising a first crank assembly rotatable about a first axis and a second crank assembly rotatable about a second axis with the first and second axes each being displaced from the other, each of the first crank assemblies comprising a first crank arm, and each of the second crank assemblies comprising a second crank arm;   a first drive shaft mechanically attached between the first crank system and the second crank system along the first axis;   a second drive shaft attached between the first crank system and the second crank system along the second axis;   a synchronous control system assembly mechanically coupled to the first crank system in a configuration that allows for 360 degrees of synchronous rotation of the first and second crank assemblies, wherein each first crank arm of each first crank assembly rotates in the same direction as the second crank arm of each second crank assembly by the synchronous control system assembly;   a pair of pedal arms, one coupled to the first crank system and the other coupled to the second crank system, each of the pair of pedal arms being pivotally coupled at a first end to the first crank arm of the first crank assembly and being pivotally coupled at a second end to a pedal;   a pair of movable crank links, one corresponding to each of the first and second crank systems, each of the pair of movable crank links comprising a first attachment point, a second attachment point, and a flexible attachment between the first attachment point and second attachment point, wherein the first attachment point of each movable crank link is pivotally coupled to the pedal arm of its corresponding crank system and the second attachment point of each movable crank is pivotally coupled to the second crank arm of its corresponding second crank assembly.   
     
     
         2 . The system of  claim 1 , wherein each of the movable crank links of the pair of movable crank links comprises a first link and a second link, wherein the first attachment point of the movable crank link is proximal to a first end of the first link and the second attachment point of the movable crank link is proximal to a first end the second link, and the attachment point comprises a pivoting attachment of the first and second links. 
     
     
         3 . The system of  claim 2 , wherein the pivoting attachment of the first and second links is at a medial location of both the first and second links, such that a second end of the first link distal from the first attachment point extends past the attachment point and second end of the second link distal to the second attachment point extends past the attachment point. 
     
     
         4 . The system of  claim 3 , wherein a first force resistance device is attached between the second end of the first link the second end of the second link, and a second force resistance device is attached between the second end of the first link and a medial location of the second link. 
     
     
         5 . The system of  claim 3 , wherein a first force resistance device is attached between the second end of the second link the second end of the first link, and a second force resistance device is attached between the second end of the second link and a medial location of the first link. 
     
     
         6 . The system of  claim 2 , wherein a first force resistance device is attached between the first link and the second link at a point on each link between the attachment points and the pivoting attachment. 
     
     
         7 . The system of  claim 1 , wherein each of the movable crank links of the pair of movable crank links is constructed of a flexible, resilient material or materials between the attachment points, the flexible, resilient material or materials allowing either for compression, expansion, or both, of a distance between the attachment points upon application of a force and return of the movable crank link to its original shape when the force is removed.