The objective of this study was to determine the efficacy and the effects of functional electrical stimulated cycling (FES cycling) in patients with spinal cord injury during their rehabilitation in a special acute care unit. Thirty patients [10 with American Spinal Injury Association Impairment Scale (AIS) grade A, three with AIS grade B, 15 with AIS grade C, two with AIS grade D] aged 44±15.5 years and 2 (median) (interquartile range, 1.0-4.25) months after spinal cord injury were included in the study. The patients participated in a 20-min FES-cycling program 2 days per week for 4 weeks during their acute inpatient rehabilitation. The influence on muscle cross-section, muscle and leg circumference, spasticity, and the walking ability parameter (distance, time, aids) was measured. Muscle stimulation intensity and output parameters (pedalling time and distance) were also recorded. Spasticity decreased during hip abduction and adduction (70 and 98.1%, respectively). Spasticity during knee flexion and knee extension decreased by 66.8 and 76.6%, and a decrease was found during dorsal foot extension (67.8%; for all, P<0.05). Presession-postsession comparisons showed that after 4 weeks of FES cycling, an increase in the circumference of the cross-sectional area of 15.3% on the left and of 17% on the right m. rectus femoris could be observed in group AIS A+B. In the AIS C+D group, the circumference of the left m. rectus femoris increased by 25% and that of the right m. rectus femoris by 21% (for all, P<0.05). The results of the study show that FES cycling in combination with function-oriented physiotherapy and occupational therapy can have a positive affect on spasticity, walking ability, and muscular reactivation. It appears to support circulatory processes within the rehabilitation of paraplegics already after a 4-week intervention.