Device with reciprocating upper extremity support assemblies

A treadmill assembly comprising:

• a treadmill surface;
• first and second rails located on opposite sides of the treadmill surface;
• first and second upper extremity support assemblies each configured for sliding movement on the first and second rails, respectively, wherein the sliding movement of the first upper extremity support assembly upon the first rail does not impact the sliding movement of the second upper extremity support assembly upon the second rail, the upper extremity support assemblies including at least one of:
• (i) first and second forearm supports operatively associated with the first and second rails, respectively, (ii) first and second sliding grips or grip handles operatively associated with the first and second rails, respectively, or (iii) a first forearm support operatively associated with the first rail and a first hand grip operatively associated with the second rail;
• and further comprising an interconnecting reverse motion linkage operatively associated with the first and second upper extremity support assemblies configured for sliding movement, the reverse motion linkage including a first engaged state configured to enable interrelated, equal movement in opposite directions of the first and second upper extremity support assemblies and a second disengaged state configured to enable independent movement of the first and second upper extremity support assemblies along the first and second rails.