Ergonomic Evaluation of Mixed Reality Interaction Modalities for Wire Harnessing Task Guidance

Nowadays, modern manufacturing industries still rely on the expertise and manual dexterity of highly skilled operators. In this context, Mixed Reality (MR) technologies are emerging as promising solutions for contextualized task guidance to support operators during complex activities. However, their effective adoption in production environments is still limited by the lack of ergonomic evidence regarding their impact on operators’ well-being, usability, and interaction sustainability. This study investigates whether different interaction modalities with holographic instructional content influence the ergonomic suitability of a MR-based task guidance system for wire harnessing, developed in collaboration with Leonardo S.p.A. A between-subjects experimental design was adopted, involving 16 industrial workers randomly assigned to two groups: gaze and gesture interaction (Group A, n = 8), and gaze and voice interaction (Group B, n = 8). Ergonomic evaluation included both physical and cognitive aspects, assessed respectively through the Simulator Sickness Questionnaire (SSQ) and a composite usability index (UI) based on ISO 9241-11, integrating efficiency, effectiveness, and satisfaction. Results suggest comparable usability levels between the two interaction modalities (UIA = 0.683; UIB = 0.667). Gesture interaction was perceived as slightly more supportive of operational efficiency, whereas voice interaction was associated with lower cybersickness severity (mean TSA = 331.5; TSB = 196.1). Overall, the findings suggest that no single interaction modality universally outperforms the other, but rather that ergonomic suitability depends on the balance between physical workload, cognitive demands, and task characteristics. These results highlight the importance of human-centered ergonomic evaluations in the design of sustainable MR assistance systems for industrial environments.