Improvements in orthostatic instability with stand locomotor training in individuals with spinal cord injury

Abstract

Prospective assessment of cardiovascular control in individuals with spinal cord injury (SCI) in response to active stand training. Cardiovascular parameters were measured at rest and in response to orthostatic challenge before and after training in individuals with clinically complete SCI. The goal of this study was to evaluate the effect of active stand training on arterial blood pressure and heart rate and changes in response to orthostatic stress in individuals with SCI. Measurements were obtained in individuals with SCI (n=8) prior to and after 40 and 80 sessions of the standing component of a locomotor training intervention (stand LT). During standing, all participants wore a harness and were suspended by an overhead, pneumatic body weight support (BWS) system over a treadmill. Trainers provided manual facilitation as necessary at the trunk and legs. All individuals were able to bear more weight on their legs after the stand LT training. Resting arterial blood pressure significantly increased in individuals with cervical SCI after 80 training sessions. At the end of the training period, resting systolic blood pressure (BP) in individuals with cervical SCI in a seated position, increased by 24% (from 84 +/- 5 to 104 +/- 7 mmHg). Furthermore, orthostatic hypotension present in response to standing prior to training (decrease in systolic BP of 24 +/- 14 mmHg) was not evident (decrease in systolic BP of 0 +/- 11 mmHg) after 80 sessions of stand LT. Hemodynamic parameters of individuals with thoracic SCI were relatively stable prior to training and not significantly different after 80 sessions of stand LT. Improvements in resting arterial blood pressure and responses to orthostatic stress in individuals with clinically complete cervical SCI occurred following intensive stand LT training. These results may be attributed to repetitive neuromuscular activation of the legs from loading and/or conditioning of cardiovascular responses from repetitively assuming an upright posture.

FIG. 1.

Representative electromyographic (μV) activity from the soleus (SOL), tibialis anterior (TA), medial hamstrings (MH), and vastus lateralis (VL) during standing in one individual (C5, AIS A) with cervical spinal cord injury (A20) before (0 sessions, 59% body weight support [BWS]) and after (80 sessions, 34% BWS) the stand locomotor training intervention.

FIG. 2.

Effect of training on resting systolic and diastolic blood pressure in sitting position without the harness for individuals with cervical and thoracic spinal cord injury (SCI). Hemodynamic parameters were recorded prior to the training (0 sessions) and at the middle (40 sessions) and end of the active training (80 sessions). *p < 0.05, comparison of cervical versus thoracic systolic and diastolic blood pressures at each session interval (0, 40, and 80 sessions); ^#p < 0.05, within group (cervical or thoracic) comparisons of session interval (40 and 80 sessions) versus baseline (0 sessions).

FIG. 3.

Changes in systolic and diastolic blood pressure and heart rate in individuals with cervical and thoracic spinal cord injury (SCI) during assumption of standing position (sit to stand with harness) at different intervals of training. Hemodynamic parameters were recorded prior to the training (0 sessions) and at the middle (40 sessions) and end of active training (80 sessions). *p < 0.05, comparison of cervical versus thoracic systolic and diastolic blood pressures at each session interval assessment (0, 40, and 80 sessions); ^#p < 0.05, comparison of systolic and diastolic blood pressures within group (cervical or thoracic) comparisons of session interval (40 and 80 sessions) versus baseline (0 sessions).

FIG. 4.

Changes in systolic and diastolic blood pressure and heart rate in a 24-year-old man with AIS A, C5 injury during active standing before and after completion of course of training. Black bar indicates the period of assumption of the standing position with harness and body weight support (BWS).