Spring position, not just spring count

On most chairs, springs attach at several heights on the frame. A higher attachment point increases resistance and changes the assistance curve through the pedal’s travel.

This gives a chair a surprisingly wide resistance range from a small number of springs, and it is why chair settings are usually written as a spring plus a position rather than a spring alone.

Split versus solid pedals

A solid pedal moves as one unit; a split pedal has two halves that move independently. The split version allows genuine unilateral loading, which is the main tool for identifying and correcting side-to-side asymmetry.

For a studio or a clinical setting this is close to essential. For a home user with no particular asymmetry, a solid pedal is perfectly workable and slightly cheaper.

Chair pedal types
Solid pedalSplit pedal
Unilateral loadingNot possibleYes
Asymmetry workLimitedCentral capability
Clinical useRestrictedPreferred
CostLowerModest premium

Why the chair is so demanding

The chair offers a small base of support and, on classical designs, nothing to hold. Every exercise therefore has a significant stability component on top of the strength requirement.

That is the appeal and the limitation. Handled designs reduce the stability demand and make the apparatus accessible to far more clients.