High versus moderate intensity arm-crank exercise for improving oxygen uptake and cardiovascular risk factors in spinal cord injured
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Background/Aim: Spinal cord injury (SCI) is a debilitating condition which leads to loss of sensory and/or motor function of varying degrees below the level of injury. Physical inactivity is a major risk factor for developing cardiovascular disease and early death. Physical inactivity is highly prevalent in SCI population. Maximal oxygen uptake is a predictor for cardiovascular health. In studies with able-bodied, aerobic high intensity training has been found superior compared to moderate intensity, in terms of increasing oxygen uptake and reducing risk factors for CVD. Only a limited amount of studies have investigated the role of intensity of training during arm-crank exercise (ACE) in terms of effect on aerobic capacity and prevention of cardiovascular risk factors in individuals with a SCI. Therefore the primary aim of this study was to compare the effect from high-intensity ACE (i.e. 85-95% of peak heart rate) in 4 x 4 minute intervals, with isocaloric moderate intensity ACE (i.e.70% of peak heart rate) on peak oxygen uptake for individuals with chronic traumatic SCI. Secondary aims were to compare the effect from high- versus moderate intensity ACE on lipid profile, fasting glucose, hypertension and resting heart rate. Methods: 10 traumatic SCI participants volunteered for 8 weeks of ACE with 3 exercise bouts per week. The participants were randomized into two groups, high intensity ACE (85-95%HRpeak ), (N=5), and moderate intensity ACE (70 %HRpeak ), (N=5). A pre-test posttest design was used, and the participants were tested for VO2peak , lipid profile, insulin resistance, blood pressure and resting heart rate at pre- and posttest. Results: No significant difference between the high- and moderate intensity ACE in terms of VO2peak was found. Although not significant there was a favorable trend towards a higher increase in mean VO2peak in the high intensity group compared to the moderate intensity (high intensity group mean increase 8. 9% (l/min), while the moderate intensity group had a minor mean decrease of 2. 1% (l/min)) No significant difference in the blood glucose levels, blood pressure, lipid profile and resting heart rate was found between the two groups after 8 weeks of ACE. Conclusions: No significant differences were found between the high and moderate intensity groups after 8 weeks of ACE. Individual differences affect our results. Our findings indicates that eight weeks of high intensity ACE may improve the aerobic capacity for chronic SCI individuals more than moderate intensity ACE. The cardiovascular risk factors such as the lipid profile seem to be improved by exercise for SCI people, but we cannot say if the intensity is the dependent factor.