Key result
Trained spinal cord-injured individuals maintained stroke volume and mean arterial pressure during an 80-degree head-up tilt, exhibiting significantly less peripheral blood pooling compared to trained able-bodied individuals.
Why the study?
Does an orthostatic challenge alter cardiovascular and peripheral vascular responses in trained spinal cord-injured individuals compared to able-bodied individuals?
Cross-Sectional (n=23)
No
Does an orthostatic challenge alter cardiovascular and peripheral vascular responses in trained spinal cord-injured individuals compared to able-bodied individuals?
Trained spinal cord-injured individuals maintain blood pressure during orthostatic challenge through specific mechanisms involving peripheral vasoconstriction and vascular atrophy, resulting in less stroke volume change compared to able-bodied individuals.
Answers are grounded in this paper and cite their sources.
Supports training benefits for orthostatic tolerance in SCI; leaves open generalizability to untrained patients and mechanisms.
We investigated cardiovascular responses to an orthostatic challenge in trained spinal cord-injured (SCI) individuals compared to able-bodied (AB) individuals. A total of 23 subjects participated, divided into three groups: seven were trained as spinal cord-injured (Tr-SCI) individuals, seven were able-bodied individuals trained as runners (Tr-AB), and nine were untrained able-bodied individuals (UnTr-AB). We measured the cardiovascular autonomic responses in all three groups during each 5-min head-up tilt (HUT) of 0°, 40°, and 80°. Stroke volume (SV), heart rate (HR), and cardiac output (Qc) as cardiovascular responses were measured by impedance cardiography. Changes in deoxyhemoglobin (∆[HHb]) and total hemoglobin (∆[Hb tot ]) concentrations of the right medial gastrocnemius muscle were measured using near-infrared spectroscopy (NIRS). As the HUT increased from 0° to 80°, Tr-SCI group showed less change in SV at all HUT levels even if HR increased significantly. Mean arterial pressure (MAP) also did not significantly increase as tilting increased from 0° to 80°. Regarding peripheral vascular responses, the alterations of ∆[Hb tot ] from 0° to 80° were less in Tr-SCI group compared to AB individuals. There is a specific mechanism whereby blood pressure is maintained during a HUT in Tr-SCI group with the elicitation of peripheral vasoconstriction and the atrophy of the vascular vessels in paraplegic lower limbs, which would be associated with less change in SV in response to an orthostatic challenge.
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Itoh et al. (2018) conducted a cross-sectional in Spinal Cord Injury (n=23). Spinal cord injury with athletic training vs. Able-bodied individuals (trained and untrained) was evaluated on Change in total hemoglobin concentration (Δ[Hbtot]) at 80° head-up tilt (μmol/dL) (p=<0.01). Trained spinal cord-injured individuals maintained stroke volume and mean arterial pressure during an 80-degree head-up tilt, exhibiting significantly less peripheral blood pooling compared to trained able-bodied individuals.
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