Understanding and applying physical fit in user interface research & design
Rob Tannen, IDSA, Bresslergroup
Ergonomics is necessary for 3-dimensional, tangible product design where issues of physical fit
and comfort are critical. But for interaction designers in the 2-dimensional world of the display
screen, understanding physical ergonomics has largely been irrelevant. For example in most
cases, interfaces are designed for existing, defined hardware that are out of the control of the
But the continuing convergence of digital interfaces with physical products is putting interaction
designers in a position where knowledge of anthropometrics, kinesthetics, and other noncognitive
human capabilities is valuable for creating effective design solutions.
There are several trends contributing to this, including:
1. The rapid proliferation of touch screen and other gestural interfaces which combine
"direct" physical control with digital interface design. If you want to design for a finger,
you have to know how a finger works.
2. The growth of ubiquitous computing leading to an increased range of scale and form
factor in devices that contain interfaces, from traditional computers and laptops, to kiosks,
tablets, phones, interactive video walls, electronic ink and consumer appliances (to name
a few). As a result, people are interacting with interfaces in range of positions and
contexts that go beyond simply standing or sitting in front of a screen. So beyond
fingertips, knowing how people can reasonably user their bodies to hold, view, reach and
interact is valuable.
3. Computing power and bandwidth across such devices now supports more complex,
involved tasks such as data entry, long duration reading and gaming, all of which can
lead to risks for repetitive motion injuries, or at least discomfort. Having a knowledge of
the types of interactions that can cause such injuries, and how to design around them, is
4. An ever increasingly diverse range of end-users are gaining access to interactive
devices, across age, and physical characteristics. For example, the One Laptop Per
Child campaign has produced a global, kid-sized laptop. In home health care, a market
of predominately elderly users, more devices contain embedded interfaces. And ADA
and similar legislation requires that devices are accessible to users with a range of
disabilities. In other words, you need to know your user, for it is not you - a given in
interface design, a necessity in ergonomic design.
5. Last, but not least - interest. Several of the factors described above are driving many
interaction designers to explore and study the world of physical product design. For
example, the IIT Institute of Design recently hosted a "thinkering" workshop specifically to
provide "an opportunity for interaction designers to get their hands dirty with electronics,
soldering, and wiring, and learn how to interface hardware artifacts with virtual
interactions." Just as it is important to understand the electro-mechanics of hardware, it
is essential to understand the relevant mechanical attributes for the users of such
What all of these trends have in common is a growing need to accommodate human physical
characteristics and constraints in the design of digital interfaces. For the most part, this skill set is
not part of the experience of interaction designers.