BACKGROUND: Drowning remains a global health crisis, particularly in inland waters. Current safety guidelines are primarily based on research conducted in extreme cold-water conditions (5-15 °C), and there is a lack of empirical data from natural environments in temperate regions where water temperatures are relatively mild. This study aimed to assess the physiological effects of two self-rescue behaviors, staying still versus active movement, on gastrointestinal temperature (TG) in a natural river environment to refine survival strategies. METHODS: Thirteen healthy male university students were randomly assigned to either a Stay group (n = 7, stationary in a long-sitting posture) or a Move group (n = 6, continuous crawling motion) while immersed to the level of the clavicle in the Nagara River (water temperature: 19.9 ± 0.9 °C; air temperature: 32.9 ± 2.8 °C). TG was recorded every minute for 60 minutes using ingestible sensors. Data were analyzed using one-dimensional Statistical Parametric Mapping and independent t-tests. RESULTS: The Move group demonstrated a significantly longer total duration of TG increase and a significantly shorter duration of TG decrease compared to the Stay group (p = 0.045, d = 1.14). While 1D-SPM analysis showed no significant differences in time-series relative TG between groups (p > 0.05), the rate of TG increase in the Move group yielded a medium-to-large effect size (d = 0.75), suggesting a potential thermogenic benefit. CONCLUSIONS: In mildly cold-water environments around 20 °C, active movement does not induce the rapid heat loss typically observed in extreme cold. Instead, it may help maintain or increase core temperature. These findings suggest that active self-rescue by moving toward the shore is a viable and potentially superior survival strategy compared to remaining stationary.
© Copyright 2026 XVth International Symposium on Biomechanics and Medicine in Swimming Proceedings. Alle Rechte vorbehalten.