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

Abstract

Accumulating evidence shows an exacerbated incidence of cognitive impairment after spinal cord injury (SCI); however, the physiology that underlies this apparent post-SCI cognitive decline is unknown. PURPOSE: To investigate the impact of injury and 6-month full-body exercise training on neurovascular coupling in individuals with SCI. METHODS: In 24 participants with SCI and 16 controls, we investigated hemodynamic (heart rate, blood pressure, CO2) and middle cerebral artery blood flow velocity responses to a working memory task (neurovascular coupling) before and after training. Neurovascular coupling was compared across groups while accounting for injury parameters. Within individuals with SCI, 6-month changes in neurovascular coupling and its relation to changes in aerobic capacity were compared via linear mixed effect model. RESULTS: Reaction time tended to be higher in individuals with SCI, especially those with high-level (≥T4) injuries, possibly due to upper motor impairments. Neurovascular coupling was graded across task difficulty (p<0.01), while injury did not have a significant impact (group effect p=0.99, interaction p=0.70). Individuals with low-level injuries (<T4) had higher aerobic capacity than those with high-level injuries (p<0.01). Aerobic capacity increased significantly with training in both groups (p<0.01). While there was no overall significant improvement in neurovascular coupling with training at the group level, the degree of improvement was closely related to that in aerobic fitness in individuals with high-level (R2=0.19, p=0.03) but not low-level (R2=0.04, p=0.46) injuries, which translated to an increase in reaction time (R2=0.16, p=0.05). CONCLUSIONS: The apparent cognitive impairment after SCI is primarily due to physical deconditioning, rather than injury itself, and can be mitigated by aerobic exercise training. This has significant implications for long-term care and management for individuals with SCI. Supported by AHA Grant 15SDG2329000 (COT), Ellen R. and Melvin J. Gordon Center for the Cure and Treatment of Paralysis (COT). EDO was in part supported by the Harvard College Research Program.