Visually Induced Motion Sickness During Smartphone Use in Moving Metro Carriages: Effects of Posture and Viewing Duration-A Randomized Crossover Study.

BACKGROUND/

OBJECTIVES

Smartphone use during public transit is widespread, yet the combined effects of posture, viewing duration, and sex on visual fatigue and visually induced motion sickness (VIMS) under real commuting conditions remain insufficiently understood. This study examined these factors during smartphone video viewing aboard Taipei MRT carriages.

METHODS

Forty healthy young adults (20 males, 20 females) completed four randomized conditions crossing two postures (sitting, standing) and two viewing durations (15 min, 30 min). Conditions were administered in a randomized order. Critical flicker fusion frequency (CFF), visual fatigue scale (VFS) scores, viewing distance, and VIMSSQ-short change scores were assessed as primary outcomes and analyzed using three-way mixed ANOVA.

RESULTS

Viewing duration produced the largest and most consistent effects across all outcomes (η2p = 0.658-0.969): 30 min viewing yielded greater CFF reduction, higher VFS scores, shorter viewing distance, and elevated VIMS compared with 15 min viewing. Standing posture significantly increased VFS scores, shortened viewing distance, and raised VIMS relative to sitting, though its effect on CFF reduction was not statistically significant. A significant sex × viewing duration interaction emerged with regard to VFS scores, with females showing a steeper increase in subjective fatigue over time, despite no significant sex main effect for any outcome. A significant posture × viewing duration interaction for VIMS indicated that standing was associated with greater VIMS responses during prolonged viewing.

CONCLUSIONS

Prolonged viewing duration and standing posture are key contributors to smartphone-related visual and motion discomfort in metro environments. Limiting continuous viewing time and preferring a seated posture when using smartphones during commuting are recommended strategies to reduce both visual fatigue and VIMS among healthy young adults; generalizability to broader commuter populations warrants further investigation.