Stability of standing on an unstable surface

Open Access
Anders, Alisha
Area of Honors:
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Karl Maxim Newell, Thesis Supervisor
  • Steriani Elavsky, Honors Advisor
  • stability
  • unstable surface
  • body weight distribution
  • COP variability
  • COP complexity
Background: Side by side stance is a simple task for healthy adults. In order to challenge the postural control system, studies have often used unstable surfaces of support. Purpose: The focal point of this current research is to examine the influence of reduced base of support area on weight distribution and postural stability. Methods: Twelve healthy right-footed college students were recruited for the study. The participants stood on two boards with selective beam widths that had direct contact with two adjacent force platforms. On the left force platform, the beam was oriented longitudinally with a width of 2.5 cm. On the right force platform, the beam was oriented horizontally with three possible beam widths (2.5 cm, 4.0 cm, 8.5 cm). Results: .There was a non-significant effect of beam width on body weight distribution. There was a main effect for beam width on ApEn in the AP direction. The ApEn of the 2.5cm beam was significantly lower than that of the ApEn of the 4.0 cm and 8.5 cm beams. Conclusion: As the width of the horizontal beam under the right foot reduces (8.5 cm, 4.0 cm, 2.5 cm), we hypothesized more weight to be distributed in the left foot. Additionally, we predicted the complexity of COP to increase as the width of the right beam decreases. Our results failed to show significance in COP variability when testing for beam widths. When the right beam was 2.5 cm, the complexity was significantly lower than that of the beam widths 8.5 cm and 4.0 cm. One of our major findings was that the complexity in the AP direction of the 2.5 cm beam width was the smallest of the three widths. Our results provide additional evidence of the search strategies of the postural control system and the feedback and feedforward control processes in this process.