Issue link: https://industrialengineer.epubxp.com/i/777540
54 ISE Magazine | www.iise.org/ISEmagazine Research physical inactivity and repetitive move- ment all contribute to work-related musculoskeletal disorders. Researchers evaluating sit-to-stand workstations have shown a number of physiological and perceptual advantages. However, little research has been done to quantify the differences in posture and muscle loading when perform- ing static, repetitive computer tasks. In "Muscle Activity and Posture Dif- ferences in the Sit and Stand Phases of Sit-to-Stand Workstation Use: A Com- parison of Computer Configurations," Kari Babski-Reeves and Alex Calhoun at Mississippi State University present findings regarding differences in mus- culoskeletal loading in the sit and stand phases when using sit-to-stand worksta- tions. For the purpose of this study, physical differences (muscle activity, joint angles and subjective discomfort) were quanti- fied when interrupting sedentary work with short periods of standing using a sit-to-stand workstation across varying computer configurations (desktop, lap- top and docked laptop with peripher- als). Twenty-four participants (12 men and 12 women) completed three cycles of 20- to five-minute ratios of sitting to standing for each configuration while doing a simulated data entry task. Participants re-created text from a textbook into an electronic document for the entire test session. Surface elec- tromyography recorded muscle activity for the shoulders, forearm and lower back; electrogoniometers tracked back, neck and elbow angles; and surveys cap- tured changes in physical discomfort over the course of the trials. While computer configuration had no effects on musculoskeletal responses, the sit-stand phase did in fl uence muscle activity and posture. Higher muscle ac- tivity in the trapezius when seated (4.9 percent MVC) compared to standing (2.4 percent MVC) suggested an in- creased load while seated. Participants positioned themselves farther from the workstation when sitting, supporting increased static load in the arms. Phase was significant for all discom- fort ratings, with the standing portion resulting in decreased discomfort. It was concluded that sit-to-stand workstations can improve musculoskeletal comfort, though more research is needed to de- fine guidelines that will reduce potential trade-offs from changes in worker posi- tioning when seated and standing. CONTACT: Kari Babski-Reeves; kari@bagley.ms state.edu; McCain Hall, Room 260J, 479-2 Hardy Road, P.O. Box 9542, Mississippi State University, MS 39762 Deficient balance recovery response results in more falls The prevalence of obesity is growing in the industrialized world. In addition to the myriad health consequences associ- ated with obesity, individuals who are obese also fall at a higher rate and suf- fer more fall-related injuries than those who are not obese. Falls already are a leading cause of injuries in the workplace, and the iden- tification of another risk factor that con- tributes to falls is not welcome news. Aiming to better understand why in- dividuals who are obese fall at a higher rate than those who are not obese, then graduate student Christina Rossi Gar- man completed a laboratory study with Maury Nussbaum and Christopher Franck of Virginia Tech and Michael Madigan, now of Texas A&M; Universi- ty. They focused on falls due to tripping. Student researcher Alex Calhoun stands at a height-adjustable workstation used in her study of sit-stand workstations. Lead author Christina Rossi Garman prepares a subject for a gait trial prior to inducing an unexpected slip.