Abstract: A chair, infinitely or incrementally adjustable between an upright seating mode and a full-recline mode, includes a concave seating portion continuous with a convex doubly-extensible leg support portion which combine to form an ergonomicly preferred seating attitude when the chair is in a full recline mode. A synchronous belt drive system extends and retracts the legrest and footrest portions and a passive/active height adjust mechanism is provided. The legrest and footrest portions are retained in a tuck position beneath the seating area of the chair when the chair is in an upright mode. A double extension leg support mechanism is provided for extending the legrest and footrest portions relative to the degree of recline.