Increased blood pressure can reduce fatigue of thenar muscles paralyzed after spinal cord injury.
The aim of this study was to evaluate whether increases in blood pressure, and presumably muscle perfusion pressure, improve the endurance of thenar muscles paralyzed chronically by cervical spinal cord injury (SCI). Resting mean arterial pressure (MAP) was low in all eight subjects (64 +/- 2 mmHg). Muscle fatigue (force decline) was produced on 2 days by intermittent supramaximal electrical stimulation of the median nerve at 20 Hz for 2 min. During one of the fatigue tests, a concurrent sustained voluntary contraction of the contralateral elbow flexors was used to increase resting MAP (by 22%, on average). Although this change in blood pressure resulted in no significant change in mean fatigue for the group, changes in MAP with exercise (median nerve stimulation with and without voluntary contraction) correlated with changes in thenar muscle fatigue in seven subjects. For every 10% increase in MAP, fatigue was reduced by approximately 3%. The data suggest that low blood pressure after chronic cervical SCI and poor blood pressure control during exercise exacerbate the fatigability of paralyzed muscles.
Butler
Jane E
JE
Department of Neurological Surgery, The Miami Project to Cure Paralysis, University of Miami School of Medicine, 1095 NW 14th Terrace, Mail Locator R-48, Miami, Florida, 33136, USA.
Ribot-Ciscar
Edith
E
Zijdewind
Inge
I
Thomas
Christine K
CK
D000328:Adult; D001132:Arm / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D015444:Exercise / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D009126:Muscle Relaxation / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000503:physiopathology*; D010243:Paralysis / Q000503:physiopathology*; D012039:Regional Blood Flow / Q000502:physiology; D013119:Spinal Cord Injuries / Q000503:physiopathology*