dc.description.abstract | Background: Spinal cord injury (SCI) is a serious medical condition that impacts sensorimotor function and quality of life. Following SCI, individuals are subjected to various secondary complications, including cardiovascular events. Evidence showed that cardiovascular disease (CVD) is the common leading cause of death among people living with SCI. Physical inactivity in people with chronic SCI due to impaired/loss of motor function reduces cardiovascular fitness and increases multiple risk factors of CVD, including lipid profile disorder, diabetes, and elevated level of pro-inflammatory markers. Those factors play important roles in the development of CVD. Using body weight-supported treadmill training (BWSTT) as a form of aerobic exercise in people with SCI has shown promising results in improving cardiovascular fitness, as indicated by decreased resting and exercise heart rate (HR). However, the underlying mechanisms of resting and exercise HR adaptation after training are still unknown. Changes in leg muscle activity, cardiac autonomic function, lung capacity, and leg muscle spasticity after training might contribute to the change in HR, but quantitative examinations are needed. In addition, limited evidence is currently available concerning how BWSTT affects risk factors of CVD, including lipid profile, glycemic control, and levels of pro-inflammatory markers. Therefore, the objectives of this pilot study were: 1) to examine the feasibility of an 8-week walking training program using a novel assistive training device in patients with chronic SCI; 2) to examine the potential association between changes in resting and exercise HR and changes in four potential factors after 8-week walking training in individuals with chronic SCI; and 3) to collect pilot data before and after the 8-week walking training program for evaluating changes in risk markers of CVD in study participants. Methods: This study used a pilot, single-group, pretest-posttest study design. All participants received 3 sessions a week for 8 weeks of walking training, using a treadmill, body weight-supported system, and novel assistive gait training device. Feasibility measures of recruitment, retention, compliance, and participants’ performance were collected throughout the study period. Participants’ perceptions about the walking training program and assistive gait training device were evaluated at the end of the study. Measurements of resting and exercise HR, electromyographic (EMG) activity of leg muscles, frequency-domain and time-domain measures of heart rate variability (HRV), vital lung capacity, and spasticity of leg muscles were performed before and after training. In regard to changes in risk markers of CVD, levels of hemoglobin A1c (HbA1c), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), C-reactive protein (CRP), and interleukin-66(IL-6) were assessed before and after training. Results: Among 55 participants who were screened for eligibility, 15 participants agreed to enroll in the study, and a total of 11 participants completed the study. However, 3 participants withdrew from the study, and one participant was excluded from the study. Throughout the period of training, all participants were able to progress in their walking performance in terms of treadmill speed, walking distance, walking duration of the training, and percentage of body weight support. Based on responses to the end intervention questionnaire, the majority of participants showed acceptance and satisfaction with the walking training program and the use of the assistive gait training device. The change in the EMG activity of leg muscles was the only significant contributing factor to the change in exercise HR among the four factors examined. The changes in low-frequency power, high-frequency power and root mean square of the successive differences of HRV, and the change in vital lung capacity showed significant correlations with the change in resting HR. Following the walking training, levels of HbA1c, LDL-C, IL-6 significantly decreased, while the levels of HDL-C significantly increased. Conclusion: The findings of this dissertation project demonstrated the feasibility of the 8-week walking training program as well as using our novel assistive training device in individuals with chronic SCI. The significant contribution by the increase in activities of leg muscles to exercise HR adaptation supports the clinical application of walking training targeting at the improvement in cardiovascular function in individuals with chronic SCI. The exercise induced beneficial effect in modulations of cardiac autonomic function and lung capacity, which were significant contributors to resting HR adaptation. Besides, positive changes in risk markers of CVD were observed in individuals with chronic SCI following training. | |