['To examine the feasibility and potential benefits of using recumbent cross-training for nonambulatory adults with cerebral palsy (CP).', 'Observational.', 'Clinical center for CP treatment and rehabilitation.', 'Significantly motor-impaired adults with CP (N=11) with a mean age ± SD of 36.3±13.2 years and Gross Motor Function Classification System (GMFCS) levels III and IV.', 'Participants completed a 40-minute session of aerobic exercise using the NuStep Recumbent Cross Trainer, in which resistance was progressively increased at 5-minute intervals.', 'Every 5 minutes during the exercise session, heart rate, blood pressure, oxygen consumption (VO(2)), energy expenditure, and respiratory exchange ratios (RERs) were recorded along with rating of perceived exertion. Immediately after, and 24 hours postexercise, participants received a standard survey to assess levels of pain and discomfort.', 'All participants were able to complete the 40-minute exercise protocol. Five of the 11 participants achieved a heart rate of at least 60% maximum throughout the duration, 10 participants had a significant elevation in VO(2) from baseline, and all participants had elevated RER values. Six participants reported pain during exercise, but only 2 reported pain after exercise was over.'] Is recumbent cross-training a feasible and safe mode of physical activity for significantly motor-impaired adults with cerebral palsy?