TY - JOUR
T1 - Body sway at sea for two visual tasks and three stance widths
AU - Stoffregen, Thomas A.
AU - Villard, Sebastien
AU - Yu, Yawen
PY - 2009/12
Y1 - 2009/12
N2 - Background: On land, body sway is influenced by stance width (the distance between the feet) and by visual tasks engaged in during stance. While wider stance can be used to stabilize the body against ship motion and crewmembers are obliged to carry out many visual tasks while standing, the influence of these factors on the kinematics of body sway has not been studied at sea. Methods: Crewmembers of the R/V Atlantis stood on a force plate from which we obtained data on the positional variability of the center of pressure (COP). The sea state was 2 on the Beaufort scale. We varied stance width (5 cm, 17 cm, and 30 cm) and the nature of the visual tasks. In the Inspection task, participants viewed a plain piece of white paper, while in the Search task they counted the number of target letters that appeared in a block of text. Results: Search task performance was similar to reports from terrestrial studies. Variability of the COP position was reduced during the Search task relative to the Inspection task. Variability was also reduced during wide stance relative to narrow stance. The influence of stance width was greater than has been observed in terrestrial studies. Conclusions: These results suggest that two factors that influence postural sway on land (variations in stance width and in the nature of visual tasks) also influence sway at sea. We conclude that - in mild sea states - the influence of these factors is not suppressed by ship motion.
AB - Background: On land, body sway is influenced by stance width (the distance between the feet) and by visual tasks engaged in during stance. While wider stance can be used to stabilize the body against ship motion and crewmembers are obliged to carry out many visual tasks while standing, the influence of these factors on the kinematics of body sway has not been studied at sea. Methods: Crewmembers of the R/V Atlantis stood on a force plate from which we obtained data on the positional variability of the center of pressure (COP). The sea state was 2 on the Beaufort scale. We varied stance width (5 cm, 17 cm, and 30 cm) and the nature of the visual tasks. In the Inspection task, participants viewed a plain piece of white paper, while in the Search task they counted the number of target letters that appeared in a block of text. Results: Search task performance was similar to reports from terrestrial studies. Variability of the COP position was reduced during the Search task relative to the Inspection task. Variability was also reduced during wide stance relative to narrow stance. The influence of stance width was greater than has been observed in terrestrial studies. Conclusions: These results suggest that two factors that influence postural sway on land (variations in stance width and in the nature of visual tasks) also influence sway at sea. We conclude that - in mild sea states - the influence of these factors is not suppressed by ship motion.
KW - Human performance at sea
KW - Posture
KW - Stance
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U2 - 10.3357/ASEM.2538.2009
DO - 10.3357/ASEM.2538.2009
M3 - Article
C2 - 20027851
AN - SCOPUS:77649208426
SN - 0095-6562
VL - 80
SP - 1039
EP - 1043
JO - Aviation Space and Environmental Medicine
JF - Aviation Space and Environmental Medicine
IS - 12
ER -