What they are actually for

Under footwork load, the spring pulls the carriage toward the footbar and your body wants to slide with it. Shoulder rests provide the anchor point that lets you press without moving up the carriage.

They are not headrests and they are not meant to bear weight through the neck. Contact should be at the shoulder girdle, with the cervical spine free.

Why adjustability matters

A fixed spacing set for average shoulders is too wide for a small client — who then slides between the rests — and too narrow for a broad one, who gets pressure on the neck. Both are uncomfortable and both change the exercise.

Adjustable or repositionable rests solve this in a studio setting. For a single-user home machine, fixed rests that happen to fit you are perfectly fine.

Removable rests open up repertoire

Several exercises need the rests out of the way — long-box work, some prone repertoire and much of the standing vocabulary. Machines with quick-release rests handle these; machines with bolted rests do not.

If you expect to progress beyond the base repertoire, removability is worth prioritizing.