METABOLIC COST OF UNDERWATER TREADMILL WALKING IN INDIVIDUALS WITH INCOMPLETE SPINAL CORD INJURY

Abstract

Research on the metabolic demand associated with training modalities is needed for those with an incomplete spinal cord injury (iSCI) to improve rehabilitation and exercise prescription approaches. The underwater treadmill (UT) is a method of training and rehabilitation becoming more popular due to the buoyancy related weight reduction and the drag resistance to limb movement. To investigate the metabolic demand of UT exercise, those with and without iSCI (N = 8) of similar age were recruited. In the first study, oxygen uptake (VO2) and heart rate (HR) were measured when exercising at 0.5 and 0.75 mph along with self-selected speeds at ratings of perceived exertion (RPE) of 3, 5, and 7. The self-selected speeds at each respective RPE were also compared. In the second study, cardiorespiratory fitness was assessed using an RPE-regulated graded exercise test in the UT. There were no significant differences between groups in VO2 when walking at 0.5 mph, t(6) = 0.66, p = .53 and 0.75 mph, t(6) = 0.39, p = .71. The HR was similar between groups when walking at 0.5 mph, t(6) = 0.93, p = .39 and 0.75 mph, t(6) = 0.82, p = .44. The VO2 was significantly different between groups at RPE 7, t(6) = 2.70, p = .04. The HR between groups was not significantly at RPE 3, 5, or 7 (p > .05). For those without iSCI, HR and VO2 were significantly different between each RPE condition (p < .05). Self-selected speeds at each RPE were not significantly different between groups. Self-selected speeds for those without iSCI, were significantly different for each RPE condition. In the second study, mean test duration was similar between groups, t(6) = 0.59, p = .11. Peak VO2 was significantly lower for those with iSCI, t(6) = 3.81, p = .03. Peak HR and RER were similar between those with and without iSCI. Overall, UT exercise that satisfies the recommendations for aerobic activity level, as prescribed by a 1-10 RPE scale, can be safely performed by those with iSCI. The UT reduces the need for assistive devices such as harnesses, electrodes, and robotics. Further, an RPE-regulated graded exercise test in the UT can safely and effectively be used to test peak cardiorespiratory fitness among those with and without iSCI. Variability does exists between the severity of iSCI and the highest achievable VO2 during ambulatory exercise, and those with a less severe iSCI may be more suitable for testing maximal VO2. Further research is needed to develop a protocol to assess maximal VO2 in the UT, for those with and without iSCI.