TY - JOUR
T1 - Swaying to the complex motion of a visual target affects postural sway variability
AU - Sotirakis, Haralampos
AU - Patikas, Dimitrios
AU - Stergiou, Nicholas
AU - Hatzitaki, Vassilia
N1 - Funding Information:
Sotirakis Haralampos is supported by the General Secretariat for Research and Technology (GSRT) and the Hellenic Foundation for Research and Innovation (HFRI) . Dr. Stergiou Nicholas is supported by National Institutes of Health ( NIGMS/P20GM109090 ).
Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/3
Y1 - 2020/3
N2 - Background: Voluntary shifting body weight in the anteroposterior direction is an important element of daily life activities, such as rising from a chair or initiating a step. In order to accommodate the daily-life challenges of such tasks, voluntary postural sway needs to be flexible and variable. Research question: In this study we asked how whole-body tracking of a complex visual target motion with the concurrent provision of feedback modulates the variability of voluntary sway. Methods: Twenty young adults (age: 27.10 ± 9.15years, height: 170.73 ± 9.40 cm, mass: 62.84 ± 11.48 kg) performed 132 cycles of voluntary antero-posterior sway, on a force platform, under two conditions: a) self-paced sway and b) swaying while tracking the complex motion of a visual target. Magnitude and temporal structure of variability of postural sway were investigated with the Coefficient of Variance (CoV) and the fractal exponent α, respectively. This analysis was performed for sway cycle duration, amplitude and velocity. The cross-correlation function between the target and sway cycle parameters was computed as a measure of visuo-postural coupling. Results: The CoV of sway cycle amplitude, duration and velocity increased during active tracking of the complex target. Fractal exponent α increased for sway cycle amplitude but decreased for cycle duration and remained unchanged for sway velocity. The cross-correlation function revealed a consistent peak at lag+1 indicating an asynchrony between the target and sway cycle duration, while the peak cross-correlation for cycle amplitude was noted at lag 0. Significance: Swaying to the complex motion of a visual target improves the variability of sway cycle amplitude, at the cost of cycle duration. This is associated with a more synchronous spatial than temporal coupling to the visual target motion. This knowledge could inform the design of postural tracking paradigms as appropriate exercise interventions, for improving voluntary sway in populations with reduced limits of stability (i.e. older adults).
AB - Background: Voluntary shifting body weight in the anteroposterior direction is an important element of daily life activities, such as rising from a chair or initiating a step. In order to accommodate the daily-life challenges of such tasks, voluntary postural sway needs to be flexible and variable. Research question: In this study we asked how whole-body tracking of a complex visual target motion with the concurrent provision of feedback modulates the variability of voluntary sway. Methods: Twenty young adults (age: 27.10 ± 9.15years, height: 170.73 ± 9.40 cm, mass: 62.84 ± 11.48 kg) performed 132 cycles of voluntary antero-posterior sway, on a force platform, under two conditions: a) self-paced sway and b) swaying while tracking the complex motion of a visual target. Magnitude and temporal structure of variability of postural sway were investigated with the Coefficient of Variance (CoV) and the fractal exponent α, respectively. This analysis was performed for sway cycle duration, amplitude and velocity. The cross-correlation function between the target and sway cycle parameters was computed as a measure of visuo-postural coupling. Results: The CoV of sway cycle amplitude, duration and velocity increased during active tracking of the complex target. Fractal exponent α increased for sway cycle amplitude but decreased for cycle duration and remained unchanged for sway velocity. The cross-correlation function revealed a consistent peak at lag+1 indicating an asynchrony between the target and sway cycle duration, while the peak cross-correlation for cycle amplitude was noted at lag 0. Significance: Swaying to the complex motion of a visual target improves the variability of sway cycle amplitude, at the cost of cycle duration. This is associated with a more synchronous spatial than temporal coupling to the visual target motion. This knowledge could inform the design of postural tracking paradigms as appropriate exercise interventions, for improving voluntary sway in populations with reduced limits of stability (i.e. older adults).
KW - Balance
KW - Balance rehabilitation
KW - Postural tracking
KW - Posture
KW - Visual feedback
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U2 - 10.1016/j.gaitpost.2020.01.026
DO - 10.1016/j.gaitpost.2020.01.026
M3 - Article
C2 - 32028079
AN - SCOPUS:85078800043
VL - 77
SP - 125
EP - 131
JO - Gait and Posture
JF - Gait and Posture
SN - 0966-6362
ER -