The Effect of Time and Experience on Kinematics During a Simulated Sign Language Interpreting Session Using a Preferred Work to Rest Ratio

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Johnson, Ron
Musculoskeletal Disorders in Sign Language Interpreters , Work to Rest Ratio , Kinematics
Sign language interpreters (SLI) provide a vital service to the deaf community but also experience high levels of pain and suffer from career threatening musculoskeletal disorders. Balancing work and rest (recovery) may be a useful intervention to help address these concerns. This thesis addresses two specific questions, parsed out of a larger study seeking to determine ideal work to rest ratios for sign language interpreting. The aims of this specific body of work were to evaluate sign language interpreters (SLIs) perceptions of the mental and physical demands associated with different work to rest ratios; and, to measure kinematics during signing, comparing kinematic outcomes between novice and experienced SLIs and over time using the work to rest ratio that was perceived as the least demanding (as identified in aim 1). Nine novice and nine experienced interpreters participated in the study, each interpreting the same ten hours of a university level lecture, over the course of six visits to the laboratory. During each session interpreters worked (“hands in the air”) for 60 minutes, but used a different work to rest strategy in each session. These strategies ranged from 10-minute work, 10-minute rest, to 60 minutes of continuous work with no rest. During each session, participants were instrumented with motion capture and electromyography sensors while interpreting in a simulated working environment. In addition, SLIs were asked to provide feedback about their perceptions of the mental and physical demands associated with each session. The first study in this thesis reports on participant’s subjective feedback about the six different sessions (paper #1); where participants identified the 15-minute work to rest ratio as ideal. The second paper reports on kinematic data from this perceived ideal work to rest ratio (paper #2). Despite interpreting in a work to rest ratio that SLIs perceived as ideal, kinematic variables with known associations to injury risk (joint position, velocity, micro-breaks) readily exceeded reported thresholds.
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