Computer-directed functional electrical stimulation that employs closed-loop (feedback) technology has been used for rehabilitation of spinal cord injured (SCI) patients. This paper summarizes the most recent developments in our laboratory. First, the design of an adaptive control system is described, and its resultant controllability is reviewed. Second, our current results with the isokinetic leg trainer are summarized with respect to muscular strength and mass and cardiovascular changes in paraplegics and quadriplegics. Third, our current results with the exercise bicycle ergometer are summarized regarding muscular endurance and cardiovascular changes in control, paraplegic, and quadriplegic subjects. Fourth, impact vibration is reviewed as a potential technique to reverse disuse osteoporosis, and clinical case studies are cited. Fifth and finally, thermoregulatory studies are presented for the first time on control, paraplegic, and quadriplegic subjects. Conclusions are drawn regarding mechanisms and recommendations made for exercise of SCI subjects in hot and humid environments.