- Email: [email protected]
DEVELOPMENTAL CHANGES IN THE DYNAMICAL STRUCTURE OF POSTURAL SWAY DURING A PRECISION FITTING TASK
Gait and Balance 4 – Variability in Gait and Posture Control. 11:00, Room 101CD,
Presentation SM18
S247
DEVELOPMENTAL CHANGES IN THE DYNAMICAL STRUCTURE OF POSTURAL SWAY DURING A PRECISION FITTING TASK 1
Jeffrey M Haddad, 2Richard E. A. van Emmerik, 3Jonathan Wheat, 2Joseph Hamill Purdue University, USA; 2University of Massachusetts, USA; 3Sheffield Hallam University, UK. Email: [email protected]
1
INTRODUCTION Postural control and stability have traditionally been quantified using spatial measures that assess the magnitude of center of pressure (COP) sway. Results from recent research has suggests that measures that examine the higher order structure (e.g. entropy and determinism) of the COP may provide alternative information regarding postural stability and flexibility. One technique that has been used to assess COP structure is recurrence quantification analysis (RQA). Using RQA, research has found that that diseased or impoverished postural systems typically exhibit sway dynamics that are more deterministic, less stable and more complex than non-diseased or trained postural systems (1, 2). To date, it is not known how these higher order postural dynamics may change as a function of development. Changes in postural complexity or determinism in children compared to adult populations may reveal novel developmental insights into the control of posture. Additionally, most of the adult work that has examined the higher order dynamical structure of posture has used a quiet stance paradigm with various sensory or cognitive manipulations (1,2). While this paradigm has yielded important information, studies that examine this structure and modulations of posture under various manual and postural constraints are needed. Therefore, our aim was to examine the higher order dynamics of postural sway during a manual-fitting task in which precision, visual and postural task dynamics were altered in children and adults. METHODS A total of 51 participants, divided across three age groups were recruited for this study. The three age groups were 7year olds; 10-year olds and college aged adults. In all trials, participants were required to fit a block (88.9 X 88.9 mm) into either a large (130 mm) or small (100 mm) opening that was cut into an object placement board. The board was located at either a near distance (arms’ length from the subject) or a far distance (1.5 arm’s length from the subject). The order of near and far trials was counterbalanced across subjects. Within each set of near and far trials, participants were asked to fit the block through a small or large opening and under full and reduced vision conditions. The order of the vision and size manipulations was counterbalanced between participants. Center of pressure (COP) data were collected. The determinism and entropy of the COP in the anterior-posterior (AP) directions were examined using RQA analysis. An embedding dimension of 10 and delay of 5 were used to reconstruct the state space. A radius of 15% of the max distance and a line length of 3 were used to determine the RQA parameters from the distance matrix.
XXI ISB Congress, Podium Sessions, Tuesday 3 July 2007
RESULTS AND DISCUSSION The COP patterns exhibited by adults were more deterministic, and more complex (higher entropy) than those of the younger children under all experimental manipulations (Figure 1). No differences between the adults and the 10-year old children were observed in the RQA variables. For all age groups determinism and entropy decreased under more difficult task constraints (Figure 1). The greater degree of determinism in the adults contradicts results from prior postural studies using quiet stance (1). In the current study, this increase in determinism and entropy exhibited by the adult participants during a manual fitting task may be a prospective mechanism, allowing both stability and exploratory movements. Further, our results indicate that the ability to modulate expressed postural fluctuations based on task and postural constraints does not develop until after the age of seven.
Figure 1: a) Percent determinism and b) entropy of the AP COP when fitting the object through the small and large opening. REFERENCES 1. Schmit J.M, et al., Exp Brain Res 163, 370-378, 2005. 2. Schmit J.M, et al., Exp Brain Res 168, 357-367, 2006. ACKNOWLEDGEMENTS This study was supported in part by NIH fellowship 5F31NS050930-02 awarded to Jeffrey M. Haddad
Journal of Biomechanics 40(S2)
Presentation SM18
S247
DEVELOPMENTAL CHANGES IN THE DYNAMICAL STRUCTURE OF POSTURAL SWAY DURING A PRECISION FITTING TASK 1
Jeffrey M Haddad, 2Richard E. A. van Emmerik, 3Jonathan Wheat, 2Joseph Hamill Purdue University, USA; 2University of Massachusetts, USA; 3Sheffield Hallam University, UK. Email: [email protected]
1
INTRODUCTION Postural control and stability have traditionally been quantified using spatial measures that assess the magnitude of center of pressure (COP) sway. Results from recent research has suggests that measures that examine the higher order structure (e.g. entropy and determinism) of the COP may provide alternative information regarding postural stability and flexibility. One technique that has been used to assess COP structure is recurrence quantification analysis (RQA). Using RQA, research has found that that diseased or impoverished postural systems typically exhibit sway dynamics that are more deterministic, less stable and more complex than non-diseased or trained postural systems (1, 2). To date, it is not known how these higher order postural dynamics may change as a function of development. Changes in postural complexity or determinism in children compared to adult populations may reveal novel developmental insights into the control of posture. Additionally, most of the adult work that has examined the higher order dynamical structure of posture has used a quiet stance paradigm with various sensory or cognitive manipulations (1,2). While this paradigm has yielded important information, studies that examine this structure and modulations of posture under various manual and postural constraints are needed. Therefore, our aim was to examine the higher order dynamics of postural sway during a manual-fitting task in which precision, visual and postural task dynamics were altered in children and adults. METHODS A total of 51 participants, divided across three age groups were recruited for this study. The three age groups were 7year olds; 10-year olds and college aged adults. In all trials, participants were required to fit a block (88.9 X 88.9 mm) into either a large (130 mm) or small (100 mm) opening that was cut into an object placement board. The board was located at either a near distance (arms’ length from the subject) or a far distance (1.5 arm’s length from the subject). The order of near and far trials was counterbalanced across subjects. Within each set of near and far trials, participants were asked to fit the block through a small or large opening and under full and reduced vision conditions. The order of the vision and size manipulations was counterbalanced between participants. Center of pressure (COP) data were collected. The determinism and entropy of the COP in the anterior-posterior (AP) directions were examined using RQA analysis. An embedding dimension of 10 and delay of 5 were used to reconstruct the state space. A radius of 15% of the max distance and a line length of 3 were used to determine the RQA parameters from the distance matrix.
XXI ISB Congress, Podium Sessions, Tuesday 3 July 2007
RESULTS AND DISCUSSION The COP patterns exhibited by adults were more deterministic, and more complex (higher entropy) than those of the younger children under all experimental manipulations (Figure 1). No differences between the adults and the 10-year old children were observed in the RQA variables. For all age groups determinism and entropy decreased under more difficult task constraints (Figure 1). The greater degree of determinism in the adults contradicts results from prior postural studies using quiet stance (1). In the current study, this increase in determinism and entropy exhibited by the adult participants during a manual fitting task may be a prospective mechanism, allowing both stability and exploratory movements. Further, our results indicate that the ability to modulate expressed postural fluctuations based on task and postural constraints does not develop until after the age of seven.
Figure 1: a) Percent determinism and b) entropy of the AP COP when fitting the object through the small and large opening. REFERENCES 1. Schmit J.M, et al., Exp Brain Res 163, 370-378, 2005. 2. Schmit J.M, et al., Exp Brain Res 168, 357-367, 2006. ACKNOWLEDGEMENTS This study was supported in part by NIH fellowship 5F31NS050930-02 awarded to Jeffrey M. Haddad
Journal of Biomechanics 40(S2)