This is a training study in healthy volunteers to characterize gains in lower-body resistive strength and cardiovascular capacity with exercise on a Combined Countermeasure Device (CCD) we have developed for the National Space Biomedical Research Institute. The CCD is a single platform which contains interchangeable modules for cardiovascular stepping exercises and lower body resistive exercises including squats, heel raises, abductor and adductor exercises and knee extension and flexion. The platform has the capability to tilt, yaw and pitch, and to translate in three dimensions in order to challenge the neurovestibular system. The underlying goal of the project is to provide a compact and efficient exercise modality that will prevent deterioration of the cardiovascular and musculoskeletal systems, and the neurovestibular system, in long-duration spaceflights. The goal of the current study is simply to test the hypothesis that in healthy volunteers, the exercise prescription proposed for the device will improve strength and VO2 max. Subjects are tested for lower body resistive strength and V02max at baseline, then are trained for 12 weeks, and tested again at followup to test for a change. 36 subjects, allowing for a 20% attrition rate, allows sufficient power to detect 95% percent confidence intervals in the changes in the strength and V02max measures of roughly 10-20%. If we observe gains in these indices which are similar to those reported in the literature for simultaneous cardiovascular and resistive strength protocols, then we believe that there is sufficient evidence to test CCD in a bedrest model of long-duration spaceflight.