Cardiorespiratory fitness is a broadly encompassing term used as a measure of aerobic fitness and provides an overall indication of how well the lungs, heart, and muscles are able to work together to uptake oxygen from the environment and utilize it to perform work. The most common indicator of cardiorespiratory fitness is VO2peak, which represents the peak capacity to uptake and utilize oxygen during a given form of exercise. In able-bodied individuals, VO2peak is negatively related to the risk for all-cause mortality (i.e., the higher the VO2peak the less mortality) and the onset of CMD. Although there is no long-term data yet available for the field of SCI, it is likely that the same relationship between VO2peak and risk for CMD exists, especially in those with lower-level and/or incomplete injuries. Changes in cardiorespiratory fitness have been examined in response to various forms of exercise including body-weight supported treadmill training, arm cycle exercise, functional electrical stimulation exercise, and hybrid exercise (i.e., stimulation of the lower limbs and active arm exercise). Each of these will now be reviewed.