The effects of foot orthoses on the ground reaction forces during walking. Part 1

Abstract

The efficacy of functional foot orthoses can be measured in a variety of ways. This particular study looked at the effects foot orthoses had on the vertical ground reaction forces (Fz), the centre of pressure deviation (medial/lateral) and the angle of the sagittal plane ground reaction force vector (GRF) at the time of (peak 1) and (peak 2) on the force/time graph. Ten patients (fivefemale and five male) who fulfilled predetermined criteria were selected for the study. Mean age for the males was 47 (range 29–65) and 35 (range 20–54) for females. All subjects underwent a biomechanical assessment and had functional foot orthoses prescribed then fitted a few weeks later. The devices were made from a variety of materials such as polypropylene, polydor and carbon fibre. Analysis took place between three and six weeks after fitting of the devices with subjects performing five trials over both force plates with and without orthoses. The walkway was covered with paper to hide the position of the plates and ink markers were placed on the shoes at three points to identify where the foot was on the plate for every trial. Subjects wore their own shoes for each trial. Results showed on average a 3%–5% increase in the vertical (Fz) component of force at initial peak (peak 1) when wearing the orthoses. This was much less, −0.15%–0.8% at the second peak (peak 2). Alterations to the sagittal plane ground reaction force vector angle (GRF) were small (<2.78 degrees) and warrant further research as no papers relating to this parameter of measurement with foot orthoses could be found. The centre of pressure (cop) deviation varied up to approximately a centimetre at both peaks when wearing the orthoses. The author feels that the findings have implications for orthoses design in certain patient categories.