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ENVIRONMENTAL HEALTH Mighty Mouse Shows Off Powers in Human Ergonomics Though Perhaps Not Saving the Day, Touch-sensitive Computer Mouse May Be on the Way The advent of computers has brought a new kind of manual labor, one of small repetitive movements using a computer keyboard and mouse. Although those movements may seem insignificant, over time they can lead to musculoskeletal pain and injury, as anyone who has experienced carpal tunnel syndrome can testify. The lab of Jack Dennerlein (right) is helping to put a finger on what makes some computer interfaces better—and healthier—than others. Pictured are (l to r) postdoctoral fellow Devin Jindrich, research assistant Ted Becker, and Maria-Helena DiMarino and Antonio Chemor, both master's students in environmental science and engineering. Photo by Pam Murray The field of ergonomics attempts to remind the designers of our constructed environment that it can be changed to better suit the human body. Jack Dennerlein, HSPH assistant professor of ergonomics and safety in the Department of Environmental Health, is finding ways to measure the effects of computer use on human tissues. He is using that information to improve performance and decrease musculoskeletal disorders through keyboard and mouse design. In the Aug. 31 issue of Human Factors, Dennerlein evaluates a haptic mouse, which builds the sense of touch right into its interface. He believes this kind of technology, originally developed for the gaming industry, could have some use in ergonomics of the workstation as well. Maximizing the Feel of Minimal Surgery The Harvard Biomechanics Laboratory has been working with surgeons at Massachusetts General Hospital to find ways to integrate haptic technologies into minimally invasive and robotic surgery. Though these procedures offer many potential benefits by allowing remote operations and reducing trauma from large incisions, they remove the sense of touch from what traditionally was a very hands-on field. The goal of the project is to develop devices that "are able to transfer forces from the body to the surgeon's hand," said Robert Howe, the Gordon McKay professor of engineering at Harvard and director of the laboratory. Robotic surgery is becoming a reality but so far uses only visual feedback. "None of the current systems allow one to feel the forces at the instrument tips in the patient's body," Howe said. The use of haptic instruments can not only translate these forces to the hand but, in some cases, even amplify them for microsurgery procedures where the forces are especially difficult to perceive. Nicholas Stylopoulos, HMS research fellow in surgery at MGH, has worked with Howe's group to evaluate the usefulness of force feedback in blunt dissection, which involves cutting through tissues to reach vital organs. Using the instruments embedded with force sensors, "you feel the force exactly at the hand," he said. The addition of force feedback not only reduces the mental workload of the procedure but helps prevent excessive force. "It's a great safety measure," Stylopoulos said. The original computer mouse was developed in the 1970s and has changed very little since. "The mouse was a great way of getting away from command language," Dennerlein said. As a virtual pointer for the screen, it provided a way to interact with the graphical user interface. Other pointers have come onto the market, such as touchpads on laptops, and fancier versions of the mouse have added buttons, contoured shapes, and optical pointers to replace the mechanical balls. "The problem is that there's been no technology change that's really improved the performance of the mouse," he said. New Tricks Haptic technologies introduce tactile feedback into a setting where it was previously unavailable. For instance, tactile clues can help guide remotely operated robots underwater or in space. And the added sense of touch can greatly improve the capacity of minimally invasive surgical techniques, allowing surgeons to feel what the instrument is touching. The sense of touch can also be integrated into surgical training simulators to create a more realistic virtual setting. One kind of haptic mouse is available on the market that provides a small vibration when the cursor passes over select objects on the screen, such as icons and window menus. The tactile feedback reinforces the visual cues by allowing users to feel where they are. The mouse Dennerlein investigated, developed by a company called Immersion, goes a step beyond providing passive tactile information; it actually creates an attractive force field around selected targets. "Vibration feedback gives you information about where you are," Dennerlein said. "Force feedback can actually help you get there, because it can attract you to a target." The mouse greatly reduces the need for accuracy in pointing, because even when hovering near a target, the cursor slips into place. A Power Tool Dennerlein's lab tested the performance of the device on 26 people who completed a simple point-and-click task using a normal mouse and the force-feedback mouse. Most people responded positively to the extra assistance, and their speed and accuracy rose significantly when using the advanced tool. "With the force-feedback mouse, you end up on a whole new curve; you can be superhuman, through the design," he said. The goal of ergonomics, however, is not only to improve performance but to prevent injury, and the introduction of force into an activity raises the risk of musculoskeletal disorders. Because a realistic desktop would have several icons or other potential targets, Dennerlein's team introduced interfering force fields in the next study, which complicated the point-and-click task. Though subjects still performed well, they reported greater levels of discomfort, a sign that the mouse might cause pain or frustration in the long run. He is now working to quantify the physical effects, measuring the electrical activity of the hand and wrist muscles during the tasks. "We really have to think creatively about how we use these devices," Dennerlein said. "They can get in the way of what you want to do, and you don't want to get in the way of the user." But the technology has potential to improve performance in certain contexts. One promising application for the mouse is in navigating Web pages, which often have hyperlinks that are buried or difficult to spot. Another immediate use is to provide information on the screen to people with a visual impairment or to help those with a motor disability complete a task with less effort. Dennerlein is continuing to explore the promise of new technologies but cautions against adopting a nifty new gadget unless it is proven helpful. "Designers need to think about moving forward in helping people and not just adding features because they can," he said. His research also has focused on keyboards and the biomechanics of typing. Some evidence, for instance, has shown that keys with a crisper feel are better for performance and health, although most keyboards today are designed with cheaper rubber domes that feel slightly mushy. "My question is, why does shape matter? Why does that feel of the keyboard matter to the injury?" Dennerlein asked. "Not all of the injury mechanisms of these disorders are known." They can be a product of posture or environment, as well as the specific forces on tissues involved in each movement. By measuring muscle activity in subjects who are performing tasks under a variety of conditions, Dennerlein intends to begin quantifying the many effects of design on the end user. —Courtney Humphries