@incollection{Weinberg:pb,
	abstract = {
Background and Aim:
The ability to control and maintain an upright standing posture is crucial for humans interacting with their environment. Many factors, such as a fear of falling as observed when exposed to a postural threat [1], can cause changes in postural stability. The ability to quantify changes in postural stability is critical to understand psychological (and physiological) effects on balance. Therefore, the goal of the study is to use linear and nonlinear analyses to identify the effects of vision and postural threat on upright stance.

Methods:
This study involves re-examining the dataset previously reported [2]. This secondary analysis was conducted as the initial analysis did not examine the sway temporal dynamics. Twenty young healthy adults stood on a force plate mounted to a hydraulic lift at two height conditions, 0.8m (LOW) and 3.2m (HIGH). Both height conditions were performed with both eyes open (EO) and closed (EC). Participants stood quietly for 60 seconds on a force plate, and centre of pressure (COP) was calculated from ground reaction forces and moments. For the linear analyses, anterior-posterior COP root mean square (RMS) and mean power frequency (MPF) were calculated. For the nonlinear analysis, recurrence plots were generated from the COP data. These plots provided a visualization of the timepoints in which the trajectory returns to a location it has visited before. A recurrence quantification analysis (RQA) was then used to quantify the number and duration of recurrences. RQA measures included recurrence rate, determinism, entropy, and average diagonal line length.

Results:
For the linear analyses, COP RMS showed no effect of vision or of a vision-height interaction; however, a main effect of height was observed, with sway amplitude decreasing in the HIGH compared to LOW condition. For COP MPF, main effects were found for both height and vision, with frequency increasing in the HIGH compared to LOW condition, as well as increasing in EC compared to EO. For the nonlinear analysis, there was a main effect of both vision and height, with all RQA measures decreasing in the HIGH compared to LOW condition, and decreasing in EC compared to EO.

Conclusions:
Both linear and nonlinear analyses revealed differences across height and visual conditions. When standing at height, a decrease in amplitude and increase in frequency was observed, thought to resemble a stiffening strategy [1]. The decreases in RQA measures across height and visual conditions may provide additional evidence for a change in postural strategy. These changes observed across conditions might be suggestive of the participant trying to deliberately minimize their sway magnitude, but end up resulting in higher frequency and less predictable sway patterns. Given the nonlinear analysis identifies changes in visual (and height) conditions, this study shows a need to go beyond traditional linear measures when assessing balance. Nonlinear measures can enhance our understanding of postural stability and should be used in future analyses with the potential to identify changes that linear measures may not detect.

References: [1] Carpenter et al., Exp Brain Res, 2001; [2] Cleworth & Carpenter, Neurosci Lett, 2016.
Acknowledgements: Funded by VISTA and NSERC
},
	annote = {ISPGR World Congress 2022
JULY 3 -- 7, MONTREAL, CANADA

P2-X-153

https://ispgr.org/wp-content/uploads/2022/06/ISPGR_Abstracts_June21.pdf},
	author = {Sara Weinberg and Stephen Palmisano and Robert S. Allison and Taylor Cleworth},
	booktitle = {International Society of Posture and Gait Research (ISPGR) World Congress 2022},
	date-added = {2022-07-04 07:35:24 -0400},
	date-modified = {2022-07-04 07:35:24 -0400},
	keywords = {Optic flow & Self Motion (also Locomotion & Aviation)},
	pages = {381-382},
	title = {Nonlinear analysis of the effects of vision and postural threat on upright stance},
	year = {2022},
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{"_id":"pompZbbXqjxGWjz3q","bibbaseid":"weinberg-palmisano-allison-cleworth-nonlinearanalysisoftheeffectsofvisionandposturalthreatonuprightstance-2022","author_short":["Weinberg, S.","Palmisano, S.","Allison, R. S.","Cleworth, T."],"bibdata":{"bibtype":"incollection","type":"incollection","abstract":"Background and Aim: The ability to control and maintain an upright standing posture is crucial for humans interacting with their environment. Many factors, such as a fear of falling as observed when exposed to a postural threat [1], can cause changes in postural stability. The ability to quantify changes in postural stability is critical to understand psychological (and physiological) effects on balance. Therefore, the goal of the study is to use linear and nonlinear analyses to identify the effects of vision and postural threat on upright stance. Methods: This study involves re-examining the dataset previously reported [2]. This secondary analysis was conducted as the initial analysis did not examine the sway temporal dynamics. Twenty young healthy adults stood on a force plate mounted to a hydraulic lift at two height conditions, 0.8m (LOW) and 3.2m (HIGH). Both height conditions were performed with both eyes open (EO) and closed (EC). Participants stood quietly for 60 seconds on a force plate, and centre of pressure (COP) was calculated from ground reaction forces and moments. For the linear analyses, anterior-posterior COP root mean square (RMS) and mean power frequency (MPF) were calculated. For the nonlinear analysis, recurrence plots were generated from the COP data. These plots provided a visualization of the timepoints in which the trajectory returns to a location it has visited before. A recurrence quantification analysis (RQA) was then used to quantify the number and duration of recurrences. RQA measures included recurrence rate, determinism, entropy, and average diagonal line length. Results: For the linear analyses, COP RMS showed no effect of vision or of a vision-height interaction; however, a main effect of height was observed, with sway amplitude decreasing in the HIGH compared to LOW condition. For COP MPF, main effects were found for both height and vision, with frequency increasing in the HIGH compared to LOW condition, as well as increasing in EC compared to EO. For the nonlinear analysis, there was a main effect of both vision and height, with all RQA measures decreasing in the HIGH compared to LOW condition, and decreasing in EC compared to EO. Conclusions: Both linear and nonlinear analyses revealed differences across height and visual conditions. When standing at height, a decrease in amplitude and increase in frequency was observed, thought to resemble a stiffening strategy [1]. The decreases in RQA measures across height and visual conditions may provide additional evidence for a change in postural strategy. These changes observed across conditions might be suggestive of the participant trying to deliberately minimize their sway magnitude, but end up resulting in higher frequency and less predictable sway patterns. Given the nonlinear analysis identifies changes in visual (and height) conditions, this study shows a need to go beyond traditional linear measures when assessing balance. Nonlinear measures can enhance our understanding of postural stability and should be used in future analyses with the potential to identify changes that linear measures may not detect. References: [1] Carpenter et al., Exp Brain Res, 2001; [2] Cleworth & Carpenter, Neurosci Lett, 2016. Acknowledgements: Funded by VISTA and NSERC ","annote":"ISPGR World Congress 2022 JULY 3 – 7, MONTREAL, CANADA P2-X-153 https://ispgr.org/wp-content/uploads/2022/06/ISPGR_Abstracts_June21.pdf","author":[{"firstnames":["Sara"],"propositions":[],"lastnames":["Weinberg"],"suffixes":[]},{"firstnames":["Stephen"],"propositions":[],"lastnames":["Palmisano"],"suffixes":[]},{"firstnames":["Robert","S."],"propositions":[],"lastnames":["Allison"],"suffixes":[]},{"firstnames":["Taylor"],"propositions":[],"lastnames":["Cleworth"],"suffixes":[]}],"booktitle":"International Society of Posture and Gait Research (ISPGR) World Congress 2022","date-added":"2022-07-04 07:35:24 -0400","date-modified":"2022-07-04 07:35:24 -0400","keywords":"Optic flow & Self Motion (also Locomotion & Aviation)","pages":"381-382","title":"Nonlinear analysis of the effects of vision and postural threat on upright stance","year":"2022","bdsk-file-1":"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","bibtex":"@incollection{Weinberg:pb,\n\tabstract = {\nBackground and Aim:\nThe ability to control and maintain an upright standing posture is crucial for humans interacting with their environment. Many factors, such as a fear of falling as observed when exposed to a postural threat [1], can cause changes in postural stability. The ability to quantify changes in postural stability is critical to understand psychological (and physiological) effects on balance. Therefore, the goal of the study is to use linear and nonlinear analyses to identify the effects of vision and postural threat on upright stance.\n\nMethods:\nThis study involves re-examining the dataset previously reported [2]. This secondary analysis was conducted as the initial analysis did not examine the sway temporal dynamics. Twenty young healthy adults stood on a force plate mounted to a hydraulic lift at two height conditions, 0.8m (LOW) and 3.2m (HIGH). Both height conditions were performed with both eyes open (EO) and closed (EC). Participants stood quietly for 60 seconds on a force plate, and centre of pressure (COP) was calculated from ground reaction forces and moments. For the linear analyses, anterior-posterior COP root mean square (RMS) and mean power frequency (MPF) were calculated. For the nonlinear analysis, recurrence plots were generated from the COP data. These plots provided a visualization of the timepoints in which the trajectory returns to a location it has visited before. A recurrence quantification analysis (RQA) was then used to quantify the number and duration of recurrences. RQA measures included recurrence rate, determinism, entropy, and average diagonal line length.\n\nResults:\nFor the linear analyses, COP RMS showed no effect of vision or of a vision-height interaction; however, a main effect of height was observed, with sway amplitude decreasing in the HIGH compared to LOW condition. For COP MPF, main effects were found for both height and vision, with frequency increasing in the HIGH compared to LOW condition, as well as increasing in EC compared to EO. For the nonlinear analysis, there was a main effect of both vision and height, with all RQA measures decreasing in the HIGH compared to LOW condition, and decreasing in EC compared to EO.\n\nConclusions:\nBoth linear and nonlinear analyses revealed differences across height and visual conditions. When standing at height, a decrease in amplitude and increase in frequency was observed, thought to resemble a stiffening strategy [1]. The decreases in RQA measures across height and visual conditions may provide additional evidence for a change in postural strategy. These changes observed across conditions might be suggestive of the participant trying to deliberately minimize their sway magnitude, but end up resulting in higher frequency and less predictable sway patterns. Given the nonlinear analysis identifies changes in visual (and height) conditions, this study shows a need to go beyond traditional linear measures when assessing balance. Nonlinear measures can enhance our understanding of postural stability and should be used in future analyses with the potential to identify changes that linear measures may not detect.\n\nReferences: [1] Carpenter et al., Exp Brain Res, 2001; [2] Cleworth & Carpenter, Neurosci Lett, 2016.\nAcknowledgements: Funded by VISTA and NSERC\n},\n\tannote = {ISPGR World Congress 2022\nJULY 3 -- 7, MONTREAL, CANADA\n\nP2-X-153\n\nhttps://ispgr.org/wp-content/uploads/2022/06/ISPGR_Abstracts_June21.pdf},\n\tauthor = {Sara Weinberg and Stephen Palmisano and Robert S. 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