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Hypokinetic circulation in persons with paraplegia.
Patrick L Jacobs1, Edward T Mahoney, Allison Robbins
1Department of Neurological Surgery, University of Miami School of Medicine, Miami, FL 33101, USA. pjacobs@miamiproject.med.miami.edu
Medicine and Science in Sports and Exercise
|September 10, 2002
Summary
Individuals with spinal cord injury (SCI) exhibit lower cardiac output during arm-crank exercise compared to non-disabled individuals. This difference, despite higher heart rates, is linked to resting cardiovascular function in SCI.
Area of Science:
- Cardiovascular Physiology
- Exercise Science
- Spinal Cord Injury Research
Background:
- Spinal cord injury (SCI) impairs upper-extremity work capacity due to hemodynamic dysfunction.
- While higher heart rates (HR) and lower stroke volumes (SV) are noted in paraplegia during exercise, it's unclear if cardiac output (.Q) is adequately compensated compared to non-disabled (ND) individuals.
Purpose of the Study:
- To compare central cardiovascular responses (HR, SV, .Q) during arm-crank (AC) exercise in individuals with thoracic SCI and sedentary ND individuals.
- To investigate if cardiovascular compensation mechanisms maintain similar .Q levels between SCI and ND groups during AC exercise.
Main Methods:
- Twenty individuals with complete thoracic SCI (T4-T11) and 20 sedentary ND individuals underwent incremental peak AC testing.
- Metabolic analysis, HR measurement (electrocardiography), and SV assessment (transthoracic impedance) were performed during exercise.
Main Results:
- At rest, SCI subjects showed significantly lower SV and .Q (approx. 25%) compared to ND subjects, with higher HR.
- During submaximal AC exercise at matched workloads, SCI subjects had higher HR but significantly lower SV and .Q.
- Peak exercise responses revealed significantly lower SV and .Q in SCI subjects compared to ND subjects, with the exception of HR.
Conclusions:
- Cardiac output (.Q) during arm-crank exercise is significantly lower in individuals with SCI compared to non-disabled individuals, even with elevated heart rates.
- The reduced exercise .Q in SCI appears to be influenced by the cardiovascular differences observed at rest.