Which piece is NOT part of the equipment safety for a Universal Reformer?

The arc is not considered a standard safety feature of the Universal Reformer equipment. Safety elements on a Reformer are designed to protect the user from injury and enhance stability during exercises.

Shoulder stops serve as crucial safety features by ensuring that the individual's shoulders are securely positioned and that they do not slide off the reformer during movement. The footbar is also an essential component for safety, as it provides a stable anchor point for the feet during exercises, helping to prevent slipping and maintaining proper alignment. Wheels facilitate easy movement and adjustment of the reformer, but they are not classified under safety aspects directly tied to the user's experience during exercise.

In contrast, the arc is typically a versatile accessory used to modify or enhance certain exercises but does not serve a specific safety purpose in the same way as the other components. Hence, understanding the distinct roles of each part is crucial in recognizing which aspects contribute directly to equipment safety on the Universal Reformer.