Heart rate variability in individuals with thoracic spinal cord injury

Study design: Cross-sectional study. Objectives: The main goal of our study was to explore the differences in heart rate variability (HRV) while sitting between able-bodied (AB) participants and paraplegic (P) individuals. Setting: The study was conducted in the Physical Therapy department and the Physical Education and Sports department of the University of Valencia and Vall d'Hebron Hospital. Methods: To record the HRV, a 1000-Hz Suunto Oy t6 heart rate monitor was used. The data were analyzed in the temporal and frequency domains, and nonlinear analysis was performed as well. Results: We found significant differences between P and AB participants in SDNN: t(76) = 2.81, P<0.01; root mean squared of the difference of successive RR intervals: t(76) = 2.35, P<0.05; very low frequency: t(76) = 2.97, P<0.01; low frequency: t(41.06) = 2.33, P<0.05; total power of the spectrum: t(45.74) = 2.57, P<0.05; SD1: t(76) = 2.35, P<0.05; SD2: t(76) = 2.82, P<0.01. Furthermore, there is a reduced variability in the P participants who adopted a sedentary lifestyle as could be observed in detrended fluctuation1 t(40) = -2.10; P<0.05. Conclusion: Although individuals in the P group were more active in sports than the AB group, they had an altered HRV when compared with AB individuals. It could be important to develop more intense sports programs to improve cardiac vagal tone, which in turn produces a decrease in work and oxygen consumption of the heart.