Heart rate recovery is improved after locomotor training in persons with incomplete spinal cord injury: implications for health and prevention

Abstract

Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction Heart rate recovery after exercise provides meaningful information about physical fitness and prognosis in both health and disease. A more rapid decrease in heart rate after exercise has been associated with higher levels of fitness as well as better health and survival. In fact, heart rate recovery (HRR) ≤ 12 beats at one minute after maximal and sub-maximal exercise is a significant prognostic index of poorer health and survival. However, little research has examined HRR in persons with spinal cord injury (SCI) despite the need for a responsive measure of fitness and health in this population. Purpose The purpose of this study was to examine HRR before and after locomotor training (LT) in persons with SCI. Methods Twenty-nine subjects with incomplete SCI performed LT 5 days per week for 12 weeks using one of four training approaches: treadmill-based training with manual assistance (TMM), treadmill-based training with stimulation (TMS), over-ground training with stimulation (OGS), and treadmill-based training with robotic assistance (TMR). Before and after 12 weeks of LT the HRR was measured one minute after 2-3 minutes of walking at each subject’s maximal capacity. Heart rate data was captured via a recording band placed on each subjects’ chest that transmitted wireless signals to a data collection system which recorded heart rate data continuously. Results The peak HR during maximal walking of the cohort before and after LT was 75 ±15% and 71 ±14% of the age-predicted maximal HR, respectively. Fifteen of the 29 subjects (52%) had an abnormal HRR (≤ 12 beats) at baseline; following LT, HRR was improved in 11/15 (73%) of these subjects. In addition, 50% of subjects with a normal baseline HRR improved HRR after LT. There was no significant difference in HRR among training approaches at baseline or after LT. Conclusions Twelve weeks of LT was associated with an improvement in HRR in almost three-quarters of the subjects with an abnormal HRR at baseline, and HRR improved in one-half of the subjects with a normal HRR at baseline. These findings suggest that HRR may be of value for tracking fitness and prognosis in persons with SCI. Further investigation of HRR in subjects with SCI is warranted.