In footwear design, few elements are as important as the shoe last. A mechanical form that serves as a proxy for the human foot, the shoe last has existed since at least the Roman Empire. When shoes are produced, the upper (the top of the shoe) is stretched over the last to set its shape. As footwear has evolved, the requirements for lasts have become both more diverse and more precise, in order to meet the needs of different footwear categories and varied foot shapes and sizes. In this article I discuss how data-driven last design empowers brands to fully optimize their footwear production, and how FitTech® provider Volumental is leading the way.
Shoe-lasts are vital in shoe production, acting as molds that shape the shoes during the lasting step of the footwear assembly process. Typically, the shoe upper is pre-heated and then stretched over the last to take its shape. The last remains inside the shoe for a period to stabilize this new shape. In some instances, the shoe may be heated again with the last inside to ensure the upper conforms even more closely to the last's shape. The last usually stays in place during the crucial step of attaching the sole to the shoe, enabling the sole to be pressed against the shoe to ensure optimal adhesion. At the end of the assembly process, the last is removed from the shoe.
The importance of designing shoe-lasts specific to each shoe category cannot be overstated, as the fit and comfort of a shoe are heavily dependent on the category it belongs to. Different types of footwear are designed with distinct purposes and functionalities in mind, and as such, they cater to varying customer expectations regarding fit.
For instance, sports footwear such as soccer boots are expected to have a snug fit. This tightness is not merely for comfort but is essential for performance. Soccer players rely on their boots to provide stability, control, and precision during rapid movements and turns. The last used for creating soccer boots must be designed to produce a shoe that hugs the foot closely, ensuring that the shoe acts as an extension of the foot, allowing for precise control of the ball. In contrast, footwear designed for more casual or prolonged use, such as walking shoes, demands a different approach. These shoes should offer a more relaxed fit, prioritizing comfort over tightness. This specialized approach ensures that the footwear not only meets the aesthetic and functional requirements of its category but also provides the appropriate fit and comfort level expected by the customer. Using a last designed for one category of shoes to produce footwear for another category can lead to a poor fit and discomfort.
Other factors that influence the fit of footwear
The shape of the last significantly influences the fit of a shoe, but it's important to recognize that several other factors also play critical roles. Here are some of the most notable factors:
- The pressure applied to the shoe upper during the lasting process.
- The elasticity of the upper material, affecting how much the shoe shrinks after the last is removed.
- The characteristics of the padding material inside the shoe, which can impact comfort and fit.
- The duration for which the last remains in the shoe, influencing how well the shoe upper conforms to the last’s shape.
- The properties of the shoe inlay or insole, contributing to the final volume of the shoe.
The necessity of prototype testing in shoe development
The variability inherent in the materials and the assembly process makes it challenging to predict the exact fit of a shoe from its last and upper design. Therefore, the practice of prototype testing becomes indispensable in the shoe development process. The most accurate and effective method for this testing is through the use of fit and wear testers - individuals who physically try on the shoes and provide direct feedback. This hands-on approach allows for the gathering of practical, user-centric data. The feedback from these fit and wear testers is crucial in identifying areas for improvement, ensuring that the final product truly meets the needs and expectations of the end users.
The critical role of fit testers in shoe design
Fit testers play a pivotal role in the shoe development process, as their feedback directly influences the final adjustments to the shoe-last and shoe design. Therefore, it is essential that these testers are not only familiar with the expected functionality of the shoes but also that they represent a diverse range of foot shapes that mirror the target customer base.
Firstly, fit testers must have a comprehensive understanding of the intended functionality of the shoe. This means that for athletic footwear, testers should be aware of the specific performance requirements – like stability and grip for trail running shoes, or flexibility and cushioning for basketball shoes. This knowledge allows them to provide precise and relevant feedback on whether the shoe meets its functional objectives.
Secondly, the selection of fit testers must be strategically aligned with the range of shoe widths being offered. If a shoe is intended to be available in only one standard width, it is imperative to select fit testers who have the most average foot shape possible, making the shoe more likely to fit a typical customer well. If the shoe is designed to be available in multiple widths, each width option should be tested by fit testers whose foot width corresponds to that specific option. This detailed and targeted testing approach is crucial for accurately assessing the comfort and functionality of each width variant.
Volumental’s data-driven approach of selecting fit testers
Volumental, the leader in footwear fitting technology, holds a significant edge in the industry with the world’s largest database of 50 million 3D foot scans from customers across more than 50 countries. Such a diverse and comprehensive collection of foot data positions Volumental uniquely to assist footwear developers in a crucial aspect of shoe design and production: the selection of fit testers.
The process of designing footwear that meets the specific needs of a target customer group requires a deep understanding of the varied foot shapes and sizes within that group. Volumental's database provides invaluable insights into this diversity, enabling footwear developers to make data-driven decisions when selecting the panel of fit testers that accurately represents the target customer population.
The following video illustrates how various feet compare to the average foot in a specific footwear market. In the visual representations, green areas on the feet indicate high similarity to the average foot. Conversely, red areas signify regions where the foot has greater volume than average, while blue areas show where the volume is less. For better clarity, the completely green average foot is displayed after every fit tester’s foot. Fit testers with foot scans that are primarily green most closely represent the foot characteristics of the majority of customers in this market.
Data-driven last grading
Last grading, the process of scaling a sample size shoe-last to create shoe-lasts for an entire size range, has long relied on outdated methods. Traditionally, grading tables with scaling factors, unchanged for decades, are used. The basis of these factors is often unclear, and they typically apply the same linear scaling for both width and height across all sizes.
However, our in-depth analysis of feet with varying lengths reveals critical insights:
- Different scaling factors are needed for widths and heights.
- Grading should be non-linear to more accurately follow the contours of feet in different length classes.
- Female and male lasts require distinct grading tables.
Leveraging millions of 3D foot scans, Volumental offers a revolutionary solution to footwear and shoe-last developers. We can assist in updating existing grading tables, ensuring shoes in all sizes are better tailored to the specific foot shapes of each size range.
Interested in optimizing your footwear development efforts as they relate to shoe fit? Contact us to learn how we can help you make a data-driven transformation in your shoe-last design and grading processes, as well as your wear-testing protocols.