Investigating psychosocial stress arising from marker-based optical motion capture and subsequent effects on gait.

Optical motion capture (OMC) requires participants to wear minimal clothing for precise marker placement and involves physical contact with the examiner. We investigate whether the standard OMC procedure induces psychosocial stress in participants and whether it leads to alterations in their gait patterns. Thirty-nine participants took part in a between-groups gait experiment. The OMC group wore short, tight clothing and 39 markers, while the control group wore everyday clothing without markers. Gait was recorded via sagittal-plane video, and gait features (stride times, variability, ranges of motion) were computed from 2-dimensional pose estimation trajectories. Physiological and psychological state changes were assessed using salivary cortisol and self-report questionnaires at multiple time points. Marker placement led to significantly increased negative affect and decreased positive affect among OMC participants, as well as a noticeable but non-significant cortisol response that varied in intensity across individuals. The negative psychological state did not result in significant gait differences on group level, except for late stance knee flexion during slow walking, which may be attributed to reduced pose estimation accuracy due to differences in clothing between groups. Our study suggests that OMC can be used without unwanted gait alterations due to stress at group level. However, contactless measurements that allow participants to wear clothing could alleviate their perceived discomfort.