Relation of heart rate recovery to heart rate variability in persons with paraplegia

Purpose Heart rate recovery (HRR) after treadmill exercise testing is an index of cardiac autonomic activity in non-disabled persons, but it is unknown if this is also the case in individuals with spinal cord injury (SCI). We investigated the relationship between HRR after maximal arm exercise testing and resting autonomic activity in persons with paraplegia. Methods A total of 17 (male n = 9, female n = 8) active individuals with paraplegia (injury below T6) were included in the study. Frequency domain analyses of resting heart rate variability were obtained and participants completed a maximal arm exercise test. HRR was calculated as the difference between peak heart rate during the test and heart rate 1 min (HRR1) and 2 (HRR2) min after cessation of exercise. Results HRR 1 and HRR 2 were statistically significantly correlated with high-frequency (HF) power (r = 0.46, p<0.05 and r = 0.47, p<0.05) and the LF/HF ratio (r = -0.49, p<0.05 and r = -0.50, p<0.05). After adjusting for age, peak heart rate and peak oxygen uptake, HRR 2 was still significantly associated with HF power (r = 0.50, p<0.05) and the LF/HF ratio (r = -0.58, p<0.05). Conclusions These findings indicate that HRR after maximal arm exercise testing is associated with resting cardiac autonomic activity in persons with paraplegia. This would suggest that HRR after maximal arm exercise testing can be used as an index of autonomic function in this population.