Assessment of COP characteristics and force-time changes during walking in the third trimester of pregnancy
Authors: Mikeska Ondřej , Zvonař Martin , Gimunová Marta 
Published: February 2020

Purpose: The primary aim of this study was to analyse the COP characteristics and force-time changes during walking between weeks 27 and 36 of pregnancy. The secondary objective was to verify the influence of the specific orthopaedic shoes that were given to the experimental group. The experimental group wore patented J Hanák R biomechanical footwear and insoles, which are designed to help with redistribution of forces acting on foot, to support both longitudinal and transverse arches of the foot and to strengthen the foot muscles during movement.Methods: Seventy-three pregnant women participated in this study. This group was random divided into the experimental group (35 pregnant women) wearing specific orthopaedic shoes and the control group (38 pregnant women). The motor task consisted of five gait trials where two foot prints for each leg were always recorded. The participants started barefoot walking 3 m ahead of the pressure platform and finished the trial 1 m after the end of the platform in order to preserve acceleration and deceleration in gait. Participants walked at their own preferred velocity. All pedobarometric parameters were registered by Emed walkway - trademark of novel gmbh in Munich, Germany. Data processing was divided to two scrips. The first script processed data to these variables (COP characteristics): Centre of pressure index (COPI), centre of pressure excursion index (COPEI), distance (D) of COP, maximum velocity (MaV) and mean velocity (MeV) of COP. The second script processed data for ten pre-defined areas of the foot: hindfoot, midfoot, MH1-5 – metatarsal heads, big toe, second toe, toes 3, 4 and 5 with these applied variables (force-time characteristics): Force-time integral (FTI) and contact time (CT).Results: For the experimental group, in comparison between 27th week and the 36th week of gestation, we can find lower COPI for both feet, significantly only for the left foot (p=0.04). Also, significant difference in COPEI (p=0.03, p=0.03) for both feet was found. In comparison pre and post measurement we found higher values of parameters COPI and COPEI and that indicates more lateral weight shifting during the last trimester. We can distinctly register extension of D, especially for the left foot (p=0.04). Changes in velocity of COP indicate that MaV was increased for both feet (p=0.00, p=0.00) and MeV was significantly increased only for the right foot (p=0.00) in the 36 week of pregnancy. For the control group, we found no significant changes in COPI, COPEI or COP. MaV and MeV of COP were significantly increased for both feet in the 36 week of pregnancy (p=0.02, p=0.00, p=0.01, p=0.00). Higher values of MaV and MeV indicate that pregnant women accelerated their walking in the 36 week of pregnancy. Further, force-time characteristics in most cases did not reveal statistically significant changes in the last trimester.Conclusion: Over the last three months of pregnancy, significant observable changes can be found, especially through COP parameters of the experimental and the control group. We found out that the specific orthopaedic shoes given to the experimental group influenced the trajectory of COP, which could have positive health aspects. Further, certain conflicting results of our study in comparison with other similar studies only confirm that individual biomechanic and physiological developments in pregnancy affect the kinematic and kinetic aspects of walking differently.Key Words: Center of pressure, pregnancy, gait, feet