Postural instability at a simulated altitude of 5,000 m before and after an expedition to Mt. Cho-Oyu (8,201 m)

Abstract

To clarify the effects of altitude acclimatization on postural instability at altitudes, six female climbers stood with their eyes open or closed on a force-measuring platform under normoxia (NC) and hypobaric hypoxia, equivalent to a 5,000 m altitude (HC), before and after an expedition to Mt. Cho-Oyu (8,201 m). The expedition extended over 84 days. We recorded sways in the center of foot pressure, electromyograms (EMGs) of lower-leg muscles, blood components and arterial oxygen saturation (SpO(2)). Before the expedition, the maximum amplitude of sway with the eyes open and integrated EMG from the medial gastrocnemius increased for HC. After the expedition, red blood cell (from 423.4 ± 15.4 to 498.0 ± 24.5 × 10(4) μl(-1)), hemoglobin content (from 12.6 ± 0.32 to 14.5 ± 1.00 g/dl) and 2,3-diphosphoglycerate (from 1.93 ± 0.21 to 2.24 ± 0.34 μmol/ml) increased. The SpO(2) under HC increased from 69.2 ± 9.6 to 77.2 ± 10.0%. The maximum amplitude of sway with the eyes open decreased for HC. No difference in the sway path length and integrated EMGs was observed between NC and HC. These results suggest that acclimatization can improve the impaired postural stability on initial arrival at altitudes. However, it is still unclear how long acclimatization period is needed. Further studies are needed to reveal this point.

Changes in balance and joint position sense during a 12-day high altitude trek: The British Services Dhaulagiri medical research expedition

“…Measurements lasted 30 s with breaks of at least 20 s between trials [ 11 ]. Standing balance was performed with feet positioned parallel 7 cm apart and arms in the fundamental standing position during all measurements [ 8 , 10 , 12 ].…”

“…The control of static and dynamic posture involves inputs from a number of sensory inputs to the central nervous system. Although the visual and vestibular inputs have been accounted for in previous assessments of balance at high altitude [ 6 , 8 , 10 – 12 ], somatosensory inputs have received limited attention. Assessments of balance using a moving platform indicated some impairment in somatosensory input at simulated hypoxia [ 7 , 13 ].…”

The fatigue-induced alteration in postural control is larger in hypobaric than in normobaric hypoxia

“…Besides, an acute exposure to both hypobaric hypoxia (HH) and normobaric hypoxia (NH) leads to significant alteration in PC 2,4,[19][20][21] . Recently, we suggested that PC was more altered in HH than in NH 4 at rest.…”

“…To our knowledge, differences in PC have been reported only during acute passive exposure between HH and NH 4 . Since many popular sports (i.e., hiking climbing and mountain trail running) are practiced at altitude with reported effects on PC 19,20,24 , it is hence of interest to investigate the effects of a fatiguing exercise in HH vs. NH. Therefore, the main purpose of the present study was to investigate the effect of muscular fatigue in three different conditions (HH, NH, NN) on postural control in healthy subjects.…”

Pre-competition and recovery strategies in elite sport: the use of vascular occlusion and ischemic preconditioning

“…Although mechanisms were not the primary focus of the investigation by Beaven et al (2012), it was reported that ischemia can improve muscle function (Lawson & Downey 1993) as well as exercise performance and maximal O2 uptake in humans (De Groot et al 2010). It is possible that hypoxia has an effect on muscle spindle reactivity and the alterations of sensorimotor control may contribute to the observed effects on eccentric measures (Hoshikawa et al 2010). In contrast, the majority of the beneficial effects of occlusion were observed after 24h in the study completed by Beaven et al (2012), the authors suggested that the increased blood flow due to reperfusion and improved muscular O2 utilisation may have led to a more rapid return of muscle function.…”