Metabolic Cost Of Underwater Treadmill Exercise Among Individuals With Incomplete Spinal Cord Injury

PURPOSE: This study compared the VO2 associated with walking on an underwater treadmill (UT) at 0.50 and 0.75 mph as well as self-selected speeds using ratings of perceived exertion (RPE) for those with incomplete spinal cord injury (iSCI). Secondly, cardiorespiratory responses of those with iSCI were compared to non-iSCI individuals of similar sex and age to determine if HR and VO2 differed. METHODS: Healthy adult males with iSCI (n = 4) and age-matched males without (n = 4) volunteered. Each participant reported for two sessions. Water was set to 92 °F and height set to the xiphoid process. When ready, treadmill speed was set to 0.5 mph. After 3 minutes speed increased to 0.75 mph for another 3 minutes. Next, treadmill speed was adjusted, if needed, until the participant felt overall effort was at an RPE of 3. This speed was maintained for 3 minutes. This process was repeated two more times, for RPE’s of 5 and 7, consecutively. Independent samples t tests were used to compare iSCI and non-iSCI HR and VO2 at speeds of 0.5 and 0.75 mph as well as at RPE 3, 5, and 7. One-way RM ANOVAs compared HR and VO2 among speed conditions and RPE conditions (3, 5, 7) for the iSCI group and separately for the non-iSCI group. RESULTS: HR was similar between groups at each walking speed and at each RPE condition. VO2 was similar at each RPE except 7 (p = 0.04). iSCI only had similar HR and VO2 responses among RPE conditions (p > .05). Those without iSCI had differences in HR and VO2 among RPE conditions, p < .001. Each group had a significant difference between self-selected speed and RPE level. CONCLUSIONS: This is the first study to show that those with iSCI can regulate UT exercise using RPE to elicit linearly increasing HR. Thus, those with iSCI are capable of safely selecting intensities via RPE that satisfy recommendations for cardiorespiratory activity. A major limitation of this study was a low sample size. More participants may have allowed differences in statistical analyses. - Physiological Data and Speed by RPE Measure RPE Group Mean SD HR 3 iSCI 101.88 15.32 HR 3 non-iSCI 96.25 17.28 HR 5 iSCI 107.63 20.01 HR 5 non-iSCI 115.63 12.55 HR 7 iSCI 120.00 31.54 HR 7 non-iSCI 145.00 5.29 VO2 (mL/kg/min) 3 iSCI 9.06 6.19 VO2 (mL/kg/min) 3 non-iSCI 12.81 1.65 VO2 (mL/kg/min) 5 iSCI 11.31 8.15 VO2 (mL/kg/min) 5 non-iSCI 20.45 3.00 VO2 (mL/kg/min) 7 iSCI 12.99 10.58 VO2 (mL/kg/min) 7 non-iSCI 28.40* 4.34 * indicates significant between group difference (p < .05)