Get a grip: multi-method evaluation of handles for tablets on the shop floor

Tablets on the shop floor need handles because user requirements for handling differ from tablet usage in leisure time. The ergonomics of such handles is under-researched, resulting in a lack of methods for their design and evaluation. In this paper, we present a multi-method evaluation of handles for a shop floor tablet. We combine and compare results of focus groups and the Comfort Questionnaire for Hand tools (CQH) with electromyography (EMG). With a field and a laboratory study, we evaluate four handles in order to identify (i) the most ergonomically rated handle and (ii) the most efficient evaluation method. Results consist of an evaluated prototype, and data that shows the comparability of results from focus groups and questionnaires to results from EMG measurements. Classifying handles as tangible human machine interfaces, we suggest that subjective evaluation with focus groups and CQH is efficient to evaluate their ergonomic quality. Practitioner summary: A handle for a tablet used in production environment is evaluated with different methods. Results show that data from focus groups and questionnaires can be used for evaluation of usability in the future, rendering complex EMG measurements unnecessary and making usability evaluation more efficient. Abbreviation: CQH: comfort questionnaire for hand tools; EMG: electromyography; tHMI: tangible human-machine interfaces; TUI: tangible user interfaces; GUI: user interface; RMS: root mean square; MVC: maximum voluntary contraction; BB: musculus biceps brachii; FCU: musculus flexor carpi ulnaris; FCR: musculus flexor carpi radialis; BR: musculus brachioradialis; FPB: musculus flexor pollicis brevis.