Impact Of 6-month Exercise Training On Cerebrovascular Function In Persons With Spinal Cord Injury

Abstract

Persons with spinal cord injury (SCI) have a four-fold greater risk for cerebrovascular disease, suggesting that they cannot maintain steady cerebral perfusion. While disruption in autonomic control after SCI may impact cerebral vascular function, chronic physical deconditioning may also play a substantial role. If so, full-body aerobic exercise may improve cerebrovascular function in persons with SCI. PURPOSE: To assess the impact of injury and habitual, whole-body functional electric stimulation (FES)-assisted aerobic exercise training on cerebrovascular function in persons with SCI. METHODS: Baseline hemodynamic (heart rate, blood pressure, CO2) and cerebral blood flow (CBF) responses to oscillations in arterial blood pressure via low-resistance breathing (i.e. autoregulation) and progressive increases in arterial CO2 via rebreathing (i.e. vasoreactivity) were measured in 16 able-bodied controls and 30 participants with SCI (n= 15 cervical and n = 15 thoracic). Nineteen participants with SCI (n= 9 cervical and n = 10 thoracic) completed 6-months of a FES-assisted rowing exercise training program. Changes in autoregulatory function, vasoreactivity, and VO2max were compared before and after aerobic exercise training via linear mixed effect model. RESULTS: Individuals with higher level SCI had slightly lower hemodynamic variables in comparison to able-bodied and those with lower level SCI and able-bodied. Greater VO2max was related to increased vasoreactivity (R2=0.45, p<0.01) at baseline. Overall, VO2max increased significantly after training (p<0.01). Vasoreactivity also tended to increase with training, but the change was not statistically significant due to high variability. Given this, we assessed the relation between the change in VO2max and vasoreactivity in exercise “responders,” defined as those with >10% change in VO2max; n=8. In responders, an increase in VO2max was strongly associated with an increase in vasoreactivity (R2=0.72, p<.01) regardless of the level of SCI. CONCLUSION: Cerebral vasoreactivity is impaired in individuals with SCI. This impairment is primarily due to physical deconditioning, and can be improved by habitual aerobic exercise.