Abstract: The invention is directed to modules for installation in beds to adjustably support targeted body zones of a user. Modularization renders actively controlled bed technology available to a broad range of beds on the market including upgrading many users' existing beds. Bed actuation modules include one or more lift systems connected to a mechanical support which has bed mounting devices for enabling installation of the module in a broad range of bed frames. An adjustable height platform of each lift system can be raised or lowered without necessarily changing the angle of inclination thereof. Lift systems for variable support of two zones may be actuated by single actuator in a way that provides contra-acting movement of the respective mattress support surfaces. Optionally, inclusion of a sensing and inference system enables automatic control of a bed actuation module according to the inferred orientation of a user's body.