The title of our class is Biomechanics for Interactive Design. That is, we are being introduced to the field of biomechanics toward applying an understanding of the mechanics of bodies in design applications. To that end we read the paper entitled The effect of a new syringe design on the ability of rheumatoid arthritis patients to inject a biological medication co-authored by our recent guest speaker Dan Formosa.
In summary, work represented in the paper succeeds at applying an understanding of biomechanics and design to solve a narrowly defined problem — maximizing the conversion of hand strength to measurable force in a syringe. However, the paper itself fails on several counts to properly limit its scope and support its explicit and implicit arguments. Further, the design solution itself, as presented, is problematic with regard to the true goal of the project. First, I will address the success of the work as represented. Then, I will delineate the various problems with the paper and the assertions and assumptions made.
At its heart, the paper successfully demonstrates the connection of design changes between the standard R syringe and the new N syringe to an increase in injection force applied by a test population of users suffering Rheumatoid Arthritis. The numbers show quite conclusively that the new N syringe successfully translates existing hand strength to a measurably improved injection force within the study setup. The study method is sound. The improvement in force numbers is significant enough to outweigh any methodological nitpicking. The interrelation of biomechanics and design successfully led to greater injection force. Intuitively, the design changes are good ones and map well to corresponding evidence. This is commendable work involving a number of smart insights.
Beyond the preceding, however, the authors make problematic claims and also infer they have successfully solved a problem when, in fact, the solution is yet to be conclusively demonstrated.
The objective measures of force in use that the authors present are sound. However, the subjective measures of preference and comfort as collected by structured survey are notably questionable. First of all, the study participants could very likely have experienced priming effects. The N syringe is explicitly and/or implicitly presented as “new and improved” in language and appearance. This could significantly influence study participants’ opinions. Further, the study participants received an honorarium, possibly predisposing them to pleasing their study administrators. Further still, given the generally high place of medicine in our society and empathy for the target user population, the prospect of helping medical product design could sway study participants’ opinions in favor of the new design.
The authors state that the target user population, in fact, makes use of several grip styles. Only one was tested. Within this confine, the force numbers look solid and are persuasive towards the design solution. Yet, the product design cannot be considered successful given the aims of its application unless it leads to overall better injections accomplished by a larger percentage of the target population as compared to the R syringe. If the new design limits grip style and/or inhibits application of force in those grips, the design may have optimized a single grip while inhibiting force application in other grip styles and thus fails overall. It may be that the existing R syringe affords a greater level of injection success on average than the new N design. To their credit, the authors call out grip styles as well as the issue of varying injection angles, but they do not effectively scope the success of their work appropriately in context of these issues.
Finally, the most significant criticism I have to offer is in the false assigning of success in a numerically quantified ergonomic change to the larger aims of the product design. In short, if the target population does not adopt the new syringe design and, further, if the new design does not yield improved injections, the design is a failure. These are issues of user behavior and efficacy that must be addressed in the field and in a way that limits priming effects — most likely through some sort of double-blind study of statistically significant time period and test population. The authors subtly suggest and infer that their measurable success in a limited aspect of ergonomically improved design will positively correlate to behavioral change and overall injection success. This is yet to be seen.
The authors overreach in their assertions as to user comfort and preference and in their inference of a successful design intervention. Within a limited context, the application of biomechanics and ergonomic design are sound and to be commended. The other results collected are unsound, as is the larger assumption of product design success.
This paper illustrates what I believe may be a central challenge in incorporating biomechanics into interactive design. By virtue of the engineering and numbers attached to biomechanics, we may be tempted to label as a success an entire project for sake of only those aspects of a design that are quantified before us.