Honda Prelude 1990 Online Reference Owner's Manual page 7

Driver's Lumbar Support (Si)
The tower back support can
be adjusted by moving the
lever on the inner side of the
seat-back to give more or
less support.
Driver's Side Supports (Si)
Seat-back side support can be
adjusted wider or narrower by
turning the knob on the inner
side of the seat-back.
Do not try to adjust lumbar or side supports while driving. Make
the adjustment while sitting in your normal driving position before
driving away.
(cont'd)