Research indicates that adaptation to a microgravity environment includes physiological changes to the cardiovascular-respiratory, musculoskeletal, and neurosensory systems. Many of these alterations emerge even during space flights of short duration. Therefore, the advancement of manned space flight from Shuttle to Space Station Freedom (SSF) requires development of effective methods for augmenting the ability of humans to maintain functional performance. Thus, it is the goal of NASA to minimize the consequences of microgravity-induced deconditioning to provide optimal in-flight performance (intra- and extra-vehicular activities), suitable return to a pedestrian environment, and nominal physiological postflight recovery for an expeditious return-to-flight physical status. As space missions lengthen, the Shuttle programs provide vehicles for further investigation of the space-flight associated systemic decrements, development of countermeasure technology, and initiation of countermeasure treatments (pre-, in, and postflight). The SSF Exercise Countermeasures Facility will provide the on-orbit operational capability to retard some of the effects of space adaptation through the use of appropriate countermeasure modalities and prescriptions.