Healthc Inform Res.  2018 Apr;24(2):118-124. 10.4258/hir.2018.24.2.118.

Evaluation of the IngVaL Pedobarography System for Monitoring of Walking Speed

• Hellstrom
• Ã…kerberg
• Ekström M
• Folke M

• KMID: 2418180
• DOI: http://doi.org/10.4258/hir.2018.24.2.118

Abstract

OBJECTIVES
Walking speed is an important component of movement and is a predictor of health in the elderly. Pedobarography, the study of forces acting between the plantar surface of the foot and a supporting surface, is an approach to estimating walking speed even when no global positioning system signal is available. The developed portable system, Identifying Velocity and Load (IngVaL), is a cost effective alternative to commercially available pedobarography systems because it only uses three force sensing resistors. In this study, the IngVaL system was evaluated. The three variables investigated in this study were the sensor durability, the proportion of analyzable steps, and the linearity between the system output and the walking speed.
METHODS
Data was collected from 40 participants, each of whom performed five walks at five different self-paced walking speeds. The linearity between the walking speed and step frequency measured with R2 values was compared for the walking speed obtained "˜A' only using amplitude data from the force sensors, "˜B' that obtained only using the step frequency, and "˜C' that obtained by combining amplitude data for each of the 40 test participants.
RESULTS
Improvement of the wireless data transmission increased the percentage of analyzable steps from 83.1% measured with a prototype to 96.6% for IngVaL. The linearity comparison showed that the methods A, B, and C were accurate for 2, 15, and 23 participants, respectively.
CONCLUSIONS
Increased sensor durability and a higher percentage of analyzed steps indicates that IngVaL is an improvement over the prototype system. The combined strategy of amplitude and step frequency was confirmed as the most accurate method.

Keyword

Humans; Movement; Foot; Walking; Walking Speed

MeSH Terms

Aged
Foot
Geographic Information Systems
Humans
Methods
Walking*

Figure

• 

  Figure 1 The locations of the three force sensors, under the cork and leather layer, are shown as black ellipses.

• 

  Figure 2 A block diagram of the Identifying Velocity and Load (IngVaL) system. From force sensor, to data acquisition, wireless data transmission and data analysis.

• 

  Figure 3 The selection of the limits on integration. The curve shows the sum of the data from the three force sensors. The limit marked by the right-hand side of the black strip is the maximum value. The limit to the right is the lower limit, defined by being placed 50 ms to the left of the maximum. The black area is the part of the force-time integral analysed.

• 

  Figure 4 Plots of the linearity R2 values for the three methods tested for the 40 participants. (A) Amplitude data from the force sensors alone, (B) only using the step frequency, and (C) combining the amplitude data with the step frequency.

• 

  Figure 5 The Identifying Velocity and Load (IngVaL) system output data for the five self-paced walking speeds for participant #11 is shown using amplitude data (A), step frequency (B), and the combination of amplitude data and frequency (C). The relationship is linear for each of the 40 participants in the test. Participant #11 was one of the 23 participants for whom the third method was the best. A higher R2 values is better.

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