NASA: Researchers studied the effects of weightlessness simulation on rat hindlimb muscle arterioles to determine changes in arteriole remodeling and if those changes are reversible. After four weeks of hindlimb suspension, arteriole diameter was examined at immediately after and at 1- and 5-weeks post suspension. Arteriole diameters were significantly reduced immediately after suspension with recovery of arcade and transverse II arterioles by 5 weeks. Transverse V arterioles were not fully recovered at 5 weeks post suspension.