Intrasubject and intersubject variability of stabilography parameters in normal conditions and simulated space mission isolation

Abstract

The state of isolation and confinement causes several symptoms as a psycho-physiological stressor. The crew’s health and condition may play a crucial role in prolonged space sojourns success. However, it’s important to distinguish the role of microgravity from the distress aspect to better understand human physiology in training during space missions. Although stabilography is a commonly used biomechanical technique, there is not enough data on the measurement repeatability. It has already been proven that the stabilograms differ between subjects due to multiple anatomical and physiological characteristics but the intersubject variability remains unclear. The study provides statistical data on 10 different stabilography measurements of 18 participants performed on different days during an analog space mission (5 females and 4 males) and in normal conditions (5 females and 4 males). Descriptive statistics and interclass correlation were used to determine intra- and intersubject variability. Mann-Whitney test was used for group comparison. Isolation was found to significantly impact symmetry and forefoot/backfoot index in trials with eyes open and ellipse area and forefoot/backfoot index in trials with eyes closed. The results show a diverse level of stabilography parameters measurement repeatability. The least stable parameter was the ellipse area (%SD = 45.79 %) and the most stable stance symmetry (%SD = 4.60 %). The results confirm ellipse area and center of pressure path poor repeatability and relative stability of parameters describing load distribution. It also proves the importance of performing multiple trials in stabilography studies to reduce the risk of erroneous results caused by intersubject variability.