Study design: Determination of differences in the cardiorespiratory responses of tetraplegic subjects with incomplete and complete lesions during treadmill gait and endurance exercise provided by neuromuscular electrical stimulation (NMES). Differences between rest and exercise phases were also examined. Objectives: To compare the cardiorespiratory responses in tetraplegic individuals during endurance exercise in the sitting position and treadmill gait with 30-50% body weight relief, both provided by NMES. Setting: Rehabilitation Ambulatory at University Hospital, Brazil. Methods: A total of 31 tetraplegic subjects were evaluated. Individuals were separated into two groups: gait group and endurance exercise group. In the gait group (n ¼ 17), the exercise protocol consisted of three different phases: 8 min of rest, 10 min of treadmill walking using NMES and 10 min of recovery. In the endurance exercise group (n ¼ 14), the cardiorespiratory test consisted of 8 min of rest, 15 min of quadriceps endurance exercise in the sitting position by NMES and 10 min of recovery. Oxygen uptake (VO 2 ), carbon dioxide production (VCO 2 ), respiratory exchange ratio (RER), pulmonary ventilation (V E ) and heart rate (HR) were measured. Results: All parameters increased considerably in the gait group from rest to the walking phase, although individuals with incomplete lesions presented a more pronounced increase than those with complete lesion. In the gait group, for incomplete tetraplegics, the mean VO 2 peak was 0.81670.314 l/min, corresponding to 11.4173.11 ml/kg/min; the mean value for VCO 2 was 0.66070.24 l/min, mean HR was 124.54728.72 bpm and mean V E was 28.3876.28 l/min. In the endurance exercise group, for incomplete tetraplegics, the mean VO 2 peak was 0.24670.07 l/ min, corresponding to 3.8470.92 ml/kg/min; the mean value for VCO 2 was 0.20570.06 l/min, mean HR was 71.45715.51 bpm and mean V E was 11.8372.72 l/min. In the endurance exercise group, smaller differences were observed in all variables from rest to the exercise phase, compared with the large increases observed in the gait group. Conclusions: These preliminary results have shown that gait training probably improves physical capacity in tetraplegic individuals more than the endurance exercise. www.nature.com/sc injured subjects, increases the ability to perform daily activities and reduces medical complications. Neuromuscular electrical stimulation (NMES) in spinal cord injured subjects allows the activation of paralyzed muscles through electrical stimulation of intact periphery motoneurons. 3 Thus, NMES has been used extensively in order to provide walking function 4 and to study the action of the spinal cord in the control of movement, using the concept of task-oriented training, which suggests that sensory input can produce the basic motor pattern. 5 Gait training on the treadmill provides a constant rate of movement and rhythm, which stimulates the reciprocal coordination of the lower limbs. 6 Moreover, NMES activates the large muscle mass, increases str...