Cardiovascular, endocrine, and immunological responses during exercise and physiological stress in persons with spinal cord injury  

 

Kazunari Furusawa¹, Takashi Mizushima², Yuichi Umezu³, Mitsuru Yamamoto⁴, Hiroyki Okawa⁵, Takeshi Nakamura⁶, and Fumihiro Tajima⁶

¹Kibikogen Rehabilitation Center for Employment injuries, Kaga-gun, Okayama, Japan; ²Department of Rehabilitation Medicine, Hamamatsu University, School of Medicine, Hamamatsu City, Shizuoka, Japan; ³Department of Rehabilitation Medicine, Kokura Rehabilitation Hospital, Kitakyushu City, Fukuoka, Japan; ⁴Department of Rehabilitation Medicine, Saitama Medical Center, Saitama Medical University, School of Medicine, Kawagoe City, Saitama, Japan; ⁵Department of Rehabilitation and Care, Seijoh University, Aichi, Japan; ⁶Department of Rehabilitation Medicine, Wakayama Medical University, Wakayama, Japan

 

Most of persons with spinal cord injuries (SCI) have a number of medical complications.  In addition, their attenuated daily activities depend on wheelchair decrease their cardiopulmonary function and oxygen consumption, and are more likely to develop obesity, hypertension, diabetes mellitus, dislipidemia, and so on.  Our longitudinal studies throughout 20 years in SCI demonstrated that their daily exercise habits and sports activities remained and improved their oxygen consumption and muscle strength.  However, there were very few physiological researches to study their sports activities and exercise.  Therefore, we focused on cardiovascular, endocrine and immunological responses during exercise in SCI. 

The peripheral sympathetic nervous system in SCI is activated without supraspinal drive, such as autonomic dysreflexia in above T5 lesion SCI. Therefore, the descending supraspinal sympathetic neurons and afferent pathways from the contracting muscles to peripheral vessels via the medullary cardiovascular center are damaged at the cervical spinal lesion in cervical SCI.  Our study demonstrated the evoked pressor responses during static exercise in cervical SCI, therefore the sympathetic arc to peripheral vessels from muscle receptors not via mudulla might be existed. 

We have focused on peripheral natural killer cell cytotoxic activity (NKCA) and interleukin-6 during actual their sports activities.  We found that NKCA decreased after a wheelchair full-marathon race and increased after a half-marathon in SCI, and plasma IL-6 levels increased after wheelchair full and half-marathon races.  These findings show that NKCA and myokine responses in SCI are similar to those of able-bodied subjects.  However, NKCA and the plasma IL-6 in cervical SCI remained constant after 20 min arm crank ergometer exercise at 60% maximum oxygen consumption instead of significant increases of them in able-bodied.  The findings suggested that immunological and myokine responses in cervical SCI were deferent from able-bodied persons because of their muscle atrophy and impaired sympathetic nervous system.

 

Keywords: Physical inactivity, Wheelchair marathon, Natural Killer cell, Myokine