The invention provides a variety of devices for supporting at least a portion of a user's body. In some embodiments, the invention provides a support device which includes a bladder capable of containing a fluid and a post adjacent the bladder. The bladder may form a rolling diaphragm portion with the post such that when a force is applied to the bladder, the rolling diaphragm portion of the bladder rolls along the post decreasing the volume of the bladder. In some embodiments, the invention provides a post which includes a reduced cross-sectional area in comparison to an adjacent region of the post such that the resistance of the rolling diaphragm portion of the bladder to rolling movement along the post due to the applies force decreases as the bladder rolls along the reduced cross-sectional area region. In some embodiments, the support device includes a plurality of bladders and/or a plurality of posts.