Cardiorespiratory changes when balancing one's whole body on one leg with eyes closed.

Postural control system has been extensively studied in terms of somatic motor function, but little is known about its connection with human autonomic function. The purpose of this study was to determine the cardiorespiratory changes in response to the 3-min load that was performed by balancing one's whole body on one leg with eyes closed (SOLEC load) or eyes open (SOLEO load) in 11 healthy young subjects (5 males and 6 females, mean age 20.8 +/- 1.9 year). Blood pressure (BP), heart rate (HR), respiratory rate (RR), inspiratory and expiratory duration (Ti and Te), tidal volume (VT), and oxygen uptake (VO2) were measured before, during, and after the load. The SOLEC load produced significant increases in HR and systolic BP within 1 min. There were further increases in systolic and diastolic BP during the late period of the load. Metabolic rate (VO2) showed a gradual increase during the SOLEC load, indicating that the late responses would be partly due to metabolic alteration. The early responses are considered to be mediated neurally through the postural control system which receives the afferent inputs arising from vestibular system and from muscle proprioceptors of the leg. In contrast, SOLEO load caused small insignificant changes in BP, HR, VT, and VO2, suggesting that a visual input is essential for balancing a postural change. The balance test with eyes closed may have value in a clinical neurological rehabilitation setting.