Date

2022-8-10

Author

Pourreza, Elmira

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This study investigates developmental changes in active usage of a contact surface and pressure distribution beneath infants’ foot during learning of upright posture. We started studying longitudinally on 22 female and 22 male infants at their 12.5th months (1st trimester, T1) and kept on screening the same subjects at every three months (19 females and 12 males at 15.5th months (T2), 17 females and 7 males at 18.4th months (T3)), in Gazi University Hospital, Social Pediatrics Department. Each trial was fulfilled by an infant standing on a pressure pad placed on top of a force plate to collect the pressure distribution data beneath the feet for 15 sec at T1, and 25-sec at T2 and T3 and was repeated at least three times. Data collection sessions were also recorded with the camera. We expected to monitor the developmental changes at an infant’s standing experience during their 2nd-year epoch through time-frequency domain analysis metrics on the overall CoPx and CoPy signals.The stabilogram plots showed noticeable shrinkage both in AP and ML directions. The phase plane plots showed shrinkage of the pattern in both CoPx and CoPy signals, and the amplitude of the frequency density function estimates and the frequency spectrum of CoP decreased significantly by time from T1 to T3. In the next part of the study, the image processing analysis have been done on pressure pad matrices. Time and frequency domain metrics of contact area, weight, pressure, and moment arms of front, mid, and hind regions of each foot have been estimated. In the frequency domain metrics there were significant shifts of the power of pressure distribution and moment arms to the lower frequencies due to the trimesters. We observed high frequency pressure vibration at the Mid foot at all trimesters. Further, we revealed higher frequency manifestations of moment arm at Fore foot in regional CoPx, which may be pointing to the role of the Fore foot as the controller and Mid foot as the load transmitter. Moreover, nonlinear dynamic analyses have been performed and led us to calculate the characteristic metrics of the m-dimensional attractor dynamics constructed in phase space by estimating critical tau (time-delay operator) from the CoPx signal through S-average displacement method. Further, Approximate Entropy (ApEn) metric was calculated by using critical tau estimates, which showed an increase in ApEn, from T1 to T3. These metrics, which define the characteristics of the developmental stages of motor learning, will help to illuminate the evolution of upright stance.

Subject Keywords

Postural Control, Infant Biomechanics, Spatiotemporal Evolution, Infant's Foot Development, Quiet Stance

URI

https://hdl.handle.net/11511/98738

Collections

Graduate School of Natural and Applied Sciences, Thesis