Effects of exercise on autonomic cardiovascular control in individuals with chronic, motor-complete spinal cord injury: an exploratory randomised clinical trial

Study Design

Secondary analysis of a clinical trial.

Objective

To assess the impact of 6 months of arm cycle ergometry training (ACET), or body weight-supported treadmill training (BWSTT), on autonomic cardiovascular responses to a laboratory sit-up test (SUT) in individuals with chronic (≥1-year post-injury) spinal cord injury (SCI).

Setting

Tertiary Rehabilitation Centre, Vancouver, Canada.

Methods

Sixteen individuals with motor-complete (American Spinal Injury Association Impairment Scale A-B) SCI between the fourth cervical and sixth thoracic spinal cord segments, aged 39 ± 11 years, were assessed. Participants were randomized to receive 72 sessions of moderate-to-vigorous intensity ACET (n = 8) or passive BWSTT (n = 8). Changes in mean arterial pressure (finger plethysmography), hemodynamics (Modelflow® method), and heart rate/heart rate variability (HR/HRV; electrocardiography) were measured in response to a  SUT before and after 6 months of exercise training. Spontaneous cardiovagal baroreflex sensitivity (cvBRS) was assessed using the sequence method.

Results

Neither ACET nor BWSTT impacted hemodynamic responses to SUT or the incidence of orthostatic hypotension (all P > 0.36). ACET increased HR (P < 0.01, η_p² = 0.34) and high frequency (HF) power HRV responses (P < 0.01, η_p² = 0.42) to SUT following 6 months of training while BWSTT did not. Consistent with this, cvBRS improved (P < 0.05, η_p² = 0.16) only following ACET. Improvements in cvBRS were correlated with both the HR (r = 0.726, P < 0.0001) and HF power (r = −0.484, P < 0.01) responses to SUT.

Conclusion

Six months of ACET, but not BWSTT, improved cardiovagal baroreflex control of HR but had no effect on BP responses to SUT in individuals with chronic, motor-complete SCI.

Sponsorship

Canadian Institutes of Health Research (CIHR)

Clinical Trial Registration

NCT01718977