Upper-body Rowing Increases Cardiorespiratory Fitness But Not Flow-mediated Dilation In Individuals With Spinal Cord Injury

Abstract

Spinal cord injury (SCI) is often associated with low cardiorespiratory fitness (VO2peak). Traditional upper-body exercise training for individuals with SCI (e.g. arm crank exercise and wheelchair propulsion) elicits positive effects on VO2peak, while the effects on vascular health are less clear. Upper-body rowing may prove to be an effective exercise modality for improving VO2peak and vascular health, as it involves repeated contractions of a relatively large muscle mass. PURPOSE: To determine the effects of exercise training performed on a rowing ergometer modified for wheelchair users on VO2peak, resting diameter of brachial artery and flow-mediated dilation (FMD). METHODS: Fifteen participants with SCI (8 males, 7 females; level of injury: C4-L3; ASIA Impairment Scale (AIS): A-C) were randomized to a control (CON, n = 7) or exercise (EXR, n = 8) group. VO2peak, resting brachial artery lumen diameter (mm) and FMD (%) were assessed before, and after six (6 W) and 12 weeks (12 W) of three weekly sessions of moderate-to-vigorous intensity exercise. VO2peak (ml/kg/min) was determined using an incremental arm crank test until exhaustion. FMD (%) was calculated as the relative increase in brachial artery diameter (determined by high-resolution ultrasound) after five minutes of cuff occlusion. Changes in diameter were analyzed off-line using semi-automated edge-detecting software. Main effects of group and time and group-by-time interactions were examined using linear-mixed models. RESULTS: There was an interaction effect for VO2peak and resting brachial artery diameter (p < .001 and p = .016, respectively). VO2peak increased from baseline (15.1 ± 5.0 ml/kg/min) to 6 W (16.6 ± 5.3 ml/kg/min, p = .007) and 12 W (17.8 ± 6.1 ml/kg/min, p < .001) in EXR, but not in CON. Resting brachial artery diameter increased from baseline (4.8 ± 0.7 mm) to 12 W (5.1 ± 0.9 mm, p = .005) in EXR, with no changes at 6 W (5.0 ± 0.9 mm), and no changes in CON. There were no main effects or interaction effect observed for FMD. CONCLUSION: These data indicate that rowing is efficient for improving VO2peak in individuals with SCI. While resting lumen diameter increases with training, 12 weeks of rowing does not increase brachial artery endothelial function.