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.
Fig 2.
SCI: Spinal Cord Injury; VR: Virtual Reality.
Table 1.
Characterization of the sample.
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.
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.
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.