Spinal cord injury (SCI) leads to muscle atrophy, hyperreflexia and spasticity, symptoms that decrease quality of life and prevent effective rehabilitation. Previous findings from our labs found that a passive cycling exercise program, motorized bicycle exercise training (MBET), in adult spinally transected animals reduced muscle atrophy and normalized hyperreflexia. We found that MBET could prevent the onset of hyperreflexia after spinal transaction, that MBET could also be used to rescue from hyperreflexia once it had set in, and that MBET could induce savings in normalization of reflexes after MBET ceased. We also demonstrated that MBET was effective in rescuing from hyperreflexia in a chronic ASIA B SCI patient, and that short-term MBET could lead to brief savings in normalization of reflexes once MBET ceased. The proposed studies will test the ability to MBET to prevent the onset of hyperreflexia in a group of acute SCI patients trained before hyperreflexia has had a chance to set in. In addition, the proposed research will attempt to confirm the possibility that long-term MBET in chronic SCI patients will rescue from hyperreflexia once it has set in, and also produce significant savings in normalization of reflexes if carried out for long periods of time. We will also test the possibility that MBET in acute and/or chronic SCI patients could reduce or prevent muscle atrophy. The experimental design calls for assessing muscle mass using MRI scans, bone density using Dual-Energy X-ray Absortiometry (DEXA) scans, spasticity measures and electrophysiological measurements to determine low frequency habituation of the H-reflex. Assessments will be carried out before MBET, during a 25 week MBET block of time, and during a 12 week post MBET monitoring period. Changes in muscle mass, bone density, spasticity scales and H-reflex habituation will be compared across these interventions and between treated SCI victims and a group of control acute and chronic SCI victims undergoing standard of care during the same period.