Samenvatting

Wellbeing, comfort and safety in outdoor shoes have always been based on parameters that vary from person to person (male, female, weight, build, etc.). The aim of the project OutFeet was to go beyond this subjective approach by taking a merely qualitative analysis to a higher scientific level.
The aim of this study was to discover a difference in the pattern of the parameters that work on the foot during uphill, downhill and level walking. Medilogic insoles were used. This measurement system is able to measure the pressure and the pressure distribution whilst wearing the shoe.
This research was divided into two parts. In order to determine whether the Medilogic insoles are capable of measuring the exact pressure respectively to the pressure distribution, a validation study was performed first. The pressure measurements obtained by the Medilogic insoles were compared to the Kistler force plate. The Kistler force plate measures forces in X, Y and Z-axes and is considered as golden standard.
This validation study gave answer to the question: Are the pressure values given from the Medilogic insoles consistent with the golden standard force values measured by the Kistler force plate?
The calculated correlations between the two measurement equipment provided information about the accuracy of the Medilogic insoles.
For the measurements ten healthy subjects (five male, five female) with an average age and weight of 28.7 years (range of 22-40 years), 71.9 kg (56-84 kg range) and a shoe size of EU 39/40 (n = 5) and EU 43/44 (n = 5) participated.
To answer this question, three measurements were taken:
- A static measurement with known weights. This was done to calculate the amplification factor. This is the gradient of the regression line.
- A static measurement with subjects. They were told to stand alternating on their heels, toes, leaning on the medial and lateral sides of their feet and central. This was done to see if there were any differences in correlation when the insole was divided into different areas.
- A dynamic measurement in which the subject walked back and forth. This was done to see if the insoles perform in the same way while walking as during static measurements.
The conclusion of the validation study was that the Medilogic insoles are accurate for static weights, the founded correlation was 0.99. As soon as measurements were performed with persons it became clear that the insoles were not accurate for determining the absolute amount of the force. The correlation was below 0.80. This could be due to curling or shifting of the insole underneath the foot, shape differences of the foot or the sensor registration. It could have also been that the subjects did not perform the asked positions well. However, the mutual pressure distributions in the sole could be measured. Therefore, the Medilogic insoles were used for the final research.
The main question for the final research was drawn up: Which of the drafted parameters that work on the foot are significantly different at an inclination angle of +12%, 0% and -12%, in comparison to each other.
The drafted parameters are:
1. Total time step time.
2. Time difference between the beginning and the maximum force of the posterior phase.
3. Time difference between the maximum force of the posterior phase and the intersection.
4. Time difference between the intersection and maximum force of the anterior phase.
5. Ratio between the heights of the peaks.
6. Ratio between the width of the anterior- and posterior phase.
Before this main question could be answered a ramp had to be designed following the prerequisites and demands. The prerequisites came from researchers from the OutFeet project and the limitations of the Technology Centre of Ski and Alpine Sports. The demands follow from the analysis. After constructing the ramp, measurements were done to provide an answer to whether there were significant differences between uphill, downhill and level.
Based on the prerequisites and demands a single concept was created and developed into a final design.
The main question of the final research was answered with three measurements:
- A dynamic measurement in which the subject walks back and forth with 0% inclination. This is done to obtain a reference value.
- The other two dynamic measurements are done on top of a self-designed ramp. The subject walks up (+12% inclination) and down (-12% inclination) the ramp.
In some of the parameters a significant difference between the conditions was found. All the conclusions relate only to an inclination of +12%(uphill), 0%(level) and -12%(downhill).
Reasons for the different outcomes could be that the inclination of the ramp was only +12% or -12%. It could be that the steepness of the ramp was too little to give a change in the walking patterns of the subjects. Another reason could be the small group of subjects. Therefore, outliers could have influenced the results.
The subjects walked with their preferred walking speed. The way of processing data may affect the data. Whilst using MATLAB, the reference points in the graphs, except for the maximum force of the posterior phase and the maximum force of the anterior phase, are manually applied. This is not a secure way to get the correct values. Sensors register pressure only when pressure works on the middle of the sensor. For this reason, it could be that the HC was registered later than the initial contact. It could also appear that the actual TO-phase should have taken longer but the sensors did not register anything any longer.
The main question of this research was: Which of the drafted parameters that work on the foot are significantly different at an inclination angle of +12%, 0% and -12% in comparison to each other.
For all the parameter has been found at least one significant difference with in the three different conditions except from parameter 5.
Conditions of the parameters that were found to be significantly different were:
Parameter 1: The difference between uphill & downhill walking was found to be significant (0.040).
Parameter 2: The difference between uphill & downhill and uphill & level walking were found to be significant (<0.001).
Parameter 3: The difference between uphill & downhill and uphill & level walking were found to be significant (0.005).
Parameter 4: The difference between uphill & downhill (0.001) and downhill & level walking (0.002) were found to be significant.
Parameter 6: The difference between uphill & downhill and uphill & level walking were found to be significant (0.005).