Cardiac autonomic modulation in response to postural transition during a virtual reality task in individuals with spinal cord injury: A cross-sectional study

Figures

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  Fig 1. Illustrative drawing of the Easy Stand®. Representative design of the accomplishment of the Virtual Cognitive Task using the Touch Screen interface, wearing the Polar V800 chest strap heart rate receiver device. [A] sitting at rest at 0°, [B] in elevation at 45° while performing the task, [C] orthostatism at 90° while performing the task. All degrees refer to the angle between the seat and the floor.

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  Fig 2. Flowchart. SCI: Spinal Cord Injury; VR: Virtual Reality.

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  Fig 3. Representation of the mean and standard error of the time domain indices for SCI and able-bodied controls, at the three moments (Sitting rest 0°, elevation 45°, and orthostatism 90°), with and without virtual reality. SCI: spinal cord injury; VR: Virtual Reality activity; bpm: beats per minute; ms: millisecond; HR: heart rate; RR intervals: intervals between heartbeats; RMSSD: square of the root mean difference of successive RR intervals; pNN50: percentage of adjacent RR intervals with a difference in duration greater than 50 milliseconds; SDNN: standard deviation of the mean of all RR intervals over a period.

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  Fig 4. Representation of the mean and standard error of the indices of the frequency domain for SCI and able-bodied controls, at the three moments (Sitting rest 0°, elevation 45°, and orthostatism 90°), with and without virtual reality. SCI: spinal cord injury; VR: Virtual Reality activity; bpm: beats per minute; ms²: millisecond squared; HF: high frequency; LF: low frequency; LF / HF: ratio of low frequency and high frequency.

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  Fig 5. Representation of the mean and standard error of the sympathetic (SNSi), parasympathetic (PNSi), and stress (Stress index) indices for SCI and able-bodied controls, at the three moments (Sitting rest 0°, elevation 45°, and orthostatism 90°), with and without virtual reality. SCI: spinal cord injury; VR: Virtual Reality activity; PNSi: index of parasympathetic nervous system; SNSi: index of sympathetic nervous system; Stress index: geometric measure of HRV that reflects the stress of the cardiovascular system; SD1: the standard deviation of instantaneous beat-to-beat RR interval variability in ms; SD2: standard deviation of continuous long-term RR interval variability in ms; SD2/SD1: ratio of short and long RR interval variations.