Static exercise-induced increase in blood pressure in individuals with cervical spinal cord injuries

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We evaluated the afferent and reflex pathways involved in the pressor response to static exercise in subjects with cervical spinal cord injuries (SCI) at C6 to C8 level. In these subjects.the descending supraspinal sympathetic neurons and afferent pathways from the contracting muscles to peripheral vessels via the medullary cardiovascular center are damaged. We measured the mean arterial blood pressure (MBP) , heart rate (HR) and plasma concentrations of norepinephrine (NE) , epinephrine (E) , renin activity, vasopressin, aldosterone and human atrial natriuretic peptide during a 2-min period of sustained contraction of biceps brachii muscle in 7 SCI subjects and 7 age-matched ablebodied control subjects. Static exercise resulted in a significant increase in MBP (P<0.05) in both SCI (pre-exercise ; 74.7 (]SY.+-。[) 2.2, static exercise ; 81.9 (]SY.+-。[) 4.1 mmHg) and control (pre-exercise ; 101.0 (]SY.+-。[) 4.2, static exercise ; 117.0 (]SY.+-。[) 4.9 mmHg). There was no change in HR during exercise in SCI,while HR increased (P<0.05) during exercise in control subjects (pre-exercise ; 68.7 (]SY.+-。[) 3.8, static exercise ; 76.0 (]SY.+-。[) 3.1 beats/min). There were no significant changes in the hormones in SCI throughout the experiment. Based on the significant rise in MBP during exercise in SCI,our results indicate the presence of a functional cardiovascular control system in SCI subjects, which regulates the pressor response to static exercise is independent of the cardiovascular medullary control center.