Ravindra S. Goonetilleke

Effects of training and representational characteristics in icon design

Icons are a very important component of graphical user interfaces. However, icon design is still predominantly artistic in nature and as a result icon selection is generally based on usability evaluations after a set of alternative icons are developed. This process tends to be time-consuming and costly. In this research, we address the issues ofwhat should be depicted in an icon, given the function it should represent, and how training affects the performance of novice users when using an iconic interface. A set of 36 concrete icons (12 functions) were selected and tested with a total of 30 participants. The experimental results indicate that complete representations are generally superior for both untrained and trained participants. Results also show that trained participants had shorter response times when compared to untrained participants. Further analysis suggests that ambiguity, uniqueness and dominance are three important aspects to consider when designing and developing icons. Applications of this research include the design of appropriate icons for graphical user interfaces prior to usability testing and the importance of a short training period to illustrate the composition of an icon in an effort to improve the mental model associated with each design.

Foot landmarking for footwear customization

As consumers are becoming increasingly selective of what they wear on their feet, manufacturers are experiencing problems developing and fitting the right footwear. Literature suggests that shoes with a shape similar to feet may be comfortable because they attempt to maintain the feet in a neutral posture. The objective of this paper is to develop a metric to quantify mismatches between feet and lasts and also to be able to generate the two-dimensional outline of the foot using the minimum number of landmarks. Fifty Hong Kong Chinese were participants in the experiment. In addition to subject weight, height, foot length and foot width, the left foot outlines were drawn and 18 landmarks were marked on each of the two-dimensional foot outlines. A step-wise procedure was used to reduce the chosen 18 landmarks to eight, such that the mean absolute negative error (an indicator of ‘tightness’) between the foot outline and the modelled curve was 1.3 mm. These eight landmarks seem to show an improvement over those proposed by other researchers, thus showing the importance of choosing the right landmarks for modelling the foot. The positive and negative absolute errors were on average 1.8 mm and 1.3 mm respectively. Moreover, the mean errors for the toe region and for the rest of the foot were 1.7 mm and 1.6 mm respectively. The results indicate that the foot outline, an important component for footwear functionality and fitting, may be modelled using eight critical landmarks.

Foot arch characterization: a review, a new metric, and a comparison.

BACKGROUND The medial longitudinal arch of the foot is important because it helps protect the foot from injury. Researchers have developed many measures to quantify the characteristics of the arch, and there is ongoing debate about the suitability of these different metrics. This article compares the various measures related to the foot arch, including a new metric, the midfoot dorsal angle, and then investigates the differences in the dimensional measures among various foot types. METHODS The right feet of 48 healthy individuals (24 men and 24 women) were measured, and various metrics, including the arch height index, the navicular height to arch length ratio, the arch index, the footprint index, the subjective ranking, the modified arch index, the malleolar valgus index, and the midfoot dorsal angle, were determined. RESULTS Correlation analyses showed that the arch index obtained from the inked footprint has a moderate to high correlation (Pearson correlation coefficients >0.50) with all measured foot-type metrics except for the malleolar valgus index. There were no differences in participant age, stature, weight, body mass index, foot length, foot width, and midfoot height among high, normal, and low foot arches. However, the high-arched group had significantly shorter arch lengths but larger navicular heights and higher midfoot dorsal angles compared with the low-arched group. There were differences in force distributions and peak pressures as well. The rearfoot had more loading and greater peak pressure whereas the midfoot had less load in the high-arched group compared with the low-arched group. CONCLUSIONS The midfoot dorsal angle may be an appropriate metric for characterizing the foot arch because it is quick and easy to measure, without the tedious procedures associated with area calculations and dimension measurements.

Foot Shape Modeling

This study is an attempt to show how a “standard” foot can be parameterized using foot length, foot width, foot height, and a measure of foot curvature so that foot shape can be predicted using these simple anthropometric measures. The prediction model was generated using 40 Hong Kong Chinese men, and the model was validated using a different group of 25 Hong Kong Chinese men. The results show that each individual foot shape may be predicted to a mean accuracy of 2.1 mm for the left foot and 2.4 mm for the right foot. Application of this research includes the potential design and development of custom footwear without the necessity of expensive 3-D scanning of feet.

Modelling foot height and foot shape-related dimensions

The application of foot anthropometry to design good-fitting footwear has been difficult due to the lack of generalised models. This study seeks to model foot dimensions so that the characteristic shapes of feet, especially in the midfoot region, can be understood. Fifty Hong Kong Chinese adults (26 males and 24 females) participated in this study. Their foot lengths, foot widths, ball girths and foot heights were measured and then evaluated using mathematical models. The results showed that there were no significant allometry (p > 0.05) effects of foot length on ball girth and foot width. Foot height showed no direct relationship with foot length. However, a normalisation with respect to foot length and foot height resulted in a significant relationship for both males and females with R2 greater than 0.97. Due to the lack of a direct relationship between foot height and foot length, the current practice of grading shoes with a constant increase in height or proportionate scaling in response to foot length is less than ideal. The results when validated with other populations can be a significant way forward in the design of footwear that has an improved fit in the height dimension.

3D foot shape generation from 2D information

Two methods to generate an individual 3D foot shape from 2D information are proposed. A standard foot shape was first generated and then scaled based on known 2D information. In the first method, the foot outline and the foot height were used, and in the second, the foot outline and the foot profile were used. The models were developed using 40 participants and then validated using a different set of 40 participants. Results show that each individual foot shape can be predicted within a mean absolute error of 1.36 mm for the left foot and 1.37 mm for the right foot using the first method, and within a mean absolute error of 1.02 mm for the left foot and 1.02 mm for the right foot using the second method. The second method shows somewhat improved accuracy even though it requires two images. Both the methods are relatively cheaper than using a scanner to determine the 3D foot shape for custom footwear design.

Footwear Cushioning: Relating Objective and Subjective Measurements

Footwear cushioning was evaluated objectively using an impact tester and related to perceived levels of cushioning (PLC). To evaluate the perceived levels of cushioning during standing, walking, and running, 3 experiments were conducted with 20 participants in each experiment. A 7-point subjective rating scale was used to rate the perceived levels of cushioning. At the end of the experiment, the subjective perceptions of cushioning were also recorded. During standing and running, the perceived level of cushioning can be predicted from the time to peak deceleration and/or stiffness (or compression). During walking, however, the magnitude of the peak deceleration on the impact tester appears to be a good predictor of PLC. Impact characterizations can reveal important differences between materials and how they are perceived during activity. In addition, the results seem to explain and link the differences that exist in the ergonomics and biomechanics literature on cushioning. Applications of this research include the design and selection of materials for footwear, floor mats, and other supporting surfaces.

Computerized girth determination for custom footwear manufacture

Good fitting footwear requires matching not just the linear dimensions of feet but their girths as well. Footwear fitters have been using manual measurements for a long time, but the development of computerized techniques and scanner technologies have now made automatic determination of different foot dimensions feasible. The resistance to using such computer measurements has been the lack of trust in the accuracy of the data. This paper proposes an approach to obtain the necessary girths of feet in order to customize footwear. The proposed approach attempts to simulate the manual measurement procedures, and its effectiveness is assessed through an experiment with 15 foot castings. The results show that the simulated measurements can be within 5mm of the manual measurements if the measuring locations can be correctly identified. Linear regressions show that the differences between the manual measurements and the simulated measurements can be modeled with the addition of a systematic error term of less than 4mm. The computerized acquisition of foot dimensions is a useful way forward for custom shoe manufacturers.

The Quality of Footwear Fit: What we know, don't know and should know

Even though fit ranks as one of the most important considerations in the purchase of a shoe, the quality of fit has no metric and is hence poorly assessed. Manufacturers, retailers, and customers tend to use trial and error techniques to improve footwear fit. This approach is rather cumbersome and very unscientific. In this paper, we present a methodology to assess and thereby quantify footwear fit so that comfort can be predicted and consequently improved lasts and shoes can be produced that match different shapes of feet.

Pressure thresholds of the human foot: measurement reliability and effects of stimulus characteristics

Information related to reliable values of discomfort thresholds can help to improve the designs of various products. This study aimed to investigate the measurement reliabilities associated with pressure thresholds, while determining the effects of stimulus characteristics (stimulus area, indentation speed) of the human foot. An indentation apparatus was used with four sizes of indentation probes and three indentation speeds. In total, 13 locations on the right foot of 10 male and 10 female participants were tested to determine the pressure discomfort thresholds (PDT) and pressure pain thresholds (PPT). Results show that the tests had very good measurement reliability with intra-class correlations (ICC) greater than 0.8 for the PPT measurements and acceptable reliability (most ICC > 0.75, with a few between 0.5 and 0.75) for the PDT measurements, demonstrating that participants are capable of judging their pain and discomfort thresholds. Pressure sensitivity differs across locations of the foot, with the medial plantar arch of the foot being the most sensitive, followed by the dorsal surface of the foot. The heel area was the least sensitive. PPT and PDT are dependent on the stimulus characteristics of the area and the speed of indentation. A smaller area has a higher PPT and PDT, indicating significant effects of spatial summation. The increase of PDT and PPT at higher speeds may be partially explained by the increase in stiffness because foot tissue exhibits viscoelastic properties. The findings can have a significant impact on the design of footwear and other accessories for improved foot health and comfort. Statement of Relevance: This study investigated the threshold measurement reliability while determining the pressure sensitivity on the surface of the foot with varying stimulus characteristics. The findings may be very useful in the design of footwear and other accessories for improved comfort and reduced injuries.