US 6371892 B1 abstract exercising is made more comfortable and effective by providing a foot rest that has a front end which holds the ball of the user 39 s foot fixed and a back end that both cradles the user 39 s heel and allows the user to pivot his heel around the ball of his foot in a natural manner the frame of the machine can be easily and repeatedly taken apart and put back together because it has two arms which mate at a connector that can be mated and unmated by simple pivoting of the two arms application_number US 97679297 A description fig2 a 2 b 2 c and 2 d are side views of stages of a rowing cycle fig4 a and 4b are plan and side elevational views respectively of a heel strap fig5 b is a sectional view at 5 b u2014 5 b in fig5 a fig5 c is an enlarged sectional side view of a portion of the toe block indicated by a circle in fig5 b fig6 a and 6b are side elevational and top views respectively of left and right foot rests attached to an extension arm fig7 a 7 b and 7 c are diagrammatic side views of a joint.