Disclosures: Ramzi A. Alajam, PT, MPT, DPT: No financial relationships or conflicts of interest

Objective: The purpose of this study was to investigate correlations between changes in three potential factors (cardiac autonomic function, lung capacity, and muscle spasticity,) and change in resting HR after walking training program in individuals with chronic spinal cord injury (SCI).

Design: Single group, pre-post study design.

Setting: Neuromuscular Research laboratory

Participants: Nine individuals (7 men, 7 motor-complete SCI, 36±9 years old, injury level T3-L1, injury onset 10±11 years) with chronic SCI were enrolled in the study.

Interventions: Participants received a walking training program using a treadmill, a body weight-supported system, and an assistive gait training device. The training program included three sessions per week for 8 weeks, a total of 24 training sessions.

Main Outcome Measures: Resting HR, time-and frequency-domain indices of heart rate variability (HRV), vital lung capacity, and spasticity of leg muscles were assessed before and after completing 8 weeks of walking training.

Results: A moderate to strong negative correlations were found between change in vital lung capacity and change in resting HR (r= -0.774, P=.007) and between change in root mean square of the successive differences (RMSSD) for HRV and change in resting HR (r = -0.52, P=.075). There was a weak positive correlation between change in the ratio of low-frequency to high-frequency for HRV and change in resting HR (r = 0.116, P=.383). However, no correlation was found between change in leg muscle spasticity and change in resting HR (r=0.013, P=.487).

Conclusions: This study is still ongoing, and the current findings suggested that increased vital lung capacity and RMSS for HRV were significant contributors to decreased resting HR after a course of walking training. A future study with large sample size should examine the contribution of changes in these factors and other factors, such as cardiac output, cardiac ventricle function, arterial stiffness, and physical fitness, etc., to resting HR adaptation after a period of walking training.

Level of Evidence: Level I

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/potential-factors-of-heart-rate-adaptation-after-8-weeks-of-walking-training-in-individuals-with-chronic-spinal-cord-injury-preliminary-results/