Potential impact of orthotic gait exercise on natural killer cell activities in thoracic level of spinal cord-injured patients

Abstract

Stydy design: Prospective before-after trial. Objective: To examine the changes of natural killer (NK) cell activity in response to orthotic gait exercise in thoracic level of spinal cord-injured (SCI) patients. Setting: National Rehabilitation Center for Persons with Disabilities, Japan. Methods: In all, 10 thoracic level of SCI patients (ranging Th5-Th12), who experienced orthotic gait training, participated in this study. NK cell activity at an effector:target (E/T) ratio (20:1) was examined in a sample of peripheral blood taken before and just after orthotic gait exercise for 20 min. On a separate day, to evaluate the physical intensity of the orthotic gait exercise, cardiorespiratory responses at rest and during exercise were measured. Results: The resting value of the NK cell activity in our SCI patients was remarkably lower than that in normal subjects reported in previous studies. The NK cell activity was significantly increased through a 20 min orthotic gait exercise (pre versus post; 12.7 ± 5.28 versus 17.76 ± 6.71, P < 0.05). The steady-state value of oxygen (VO2) and heart rate (HR) were 18.13 ± 3.92 ml/kg and 142.53 ± 19.84 b/min, respectively. It was noteworthy that a patient who showed decrement of NK cell activity in response to exercise had the highest level of injury (Th5), and showed the higher energy cost of orthotic gait. Conclusion: These findings suggested that the orthotic gait exercise has the potential to enhance the immune function for SCI persons, although patients with a higher level of SCI may have some difficulties.