Distinctive Steady-State Heart Rate and Blood Pressure Responses to Passive Robotic Leg Exercise and Functional Electrical Stimulation during Head-Up Tilt

Frontiers in Physiology, 2016 · DOI: 10.3389/fphys.2016.00612 · Published: December 9, 2016

Spinal Cord Injury Assistive Technology Physiology

Simple Explanation

Tilt tables are used to help patients stand up, but this can cause a drop in blood pressure, especially after spinal cord injury. Robot-assisted tilt tables with leg exercises and electrical stimulation may help. This study tested whether the effect of passive leg exercise (PE) during verticalization (head-up tilt) on heart rate (HR) and blood pressure (sBP, dBP) depends on the tilt angle and if functional electrical stimulation (FES) enhances this effect. The study found that PE's effect on the cardiovascular system is dependent on the verticalization angle, and FES is not a significant contributing factor.

Study Duration

Not specified

Participants

10 healthy male subjects

Evidence Level

Not specified

Key Findings

1
Head-up tilt alone increases heart rate and diastolic blood pressure, but not systolic blood pressure.
2
Passive leg exercise during head-up tilt results in statistically significant changes in heart rate, systolic blood pressure, and diastolic blood pressure, but the effect depends on the angle.
3
Adding FES at constant intensity or varying FES intensity during passive leg exercise did not have statistically significant effects on cardiovascular parameters.

Research Summary

This study investigated the effects of passive robotic leg exercise (PE) and functional electrical stimulation (FES) on cardiovascular parameters during head-up tilt in healthy subjects. The findings indicate that the effect of PE on the cardiovascular system during head-up tilt is strongly dependent on the verticalization angle. The study concludes that orthostatic hypotension cannot be prevented by PE alone, and FES is not a significant contributing factor to the PE effect.

Practical Implications

Rehabilitation Strategies

The verticalization angle of robot-assisted tilt tables should be carefully considered to optimize the cardiovascular benefits of passive leg exercise.

Clinical Practice

Relying solely on passive leg exercise may not be sufficient to prevent orthostatic hypotension during tilt table therapy; additional interventions might be necessary.

Future Research

Further studies are needed to investigate the dependency of the PE effect on the tilt angle in patient populations with cardiovascular disease or complications.

Study Limitations

1
The study was performed on a small sample size of healthy subjects.
2
The generalizability of the findings to patients with cardiovascular disease or complications is unclear.
3
The reported p-values were not adjusted for multiplicity.

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