PRESS RELEASE
The Open Sports Sciences Journal
NEWS RELEASE: 22-07-2026
The study, "Feasibility of Physiological Assessments for Long-Distance Swimming Safety in Open Water Using Virtual Reality Settings," was carried out by Hiroki Hamada, Yuko Nakao, Takashi Yamagata, Takayuki Torigoe, Chihiro Watanabe, Masato Kawashima, Eri Oyanagi, Makoto Tajima, Toshihiro Wakimoto, Takeshi Yoda, Michael J. Kremenik, Hisashi Miyazaki, and Hiromi Yano in The Open Sports Sciences Journal.
A Japanese research team has demonstrated for the first time that it is possible to monitor the heart rates of 40 swimmers continuously and in real time during long-distance open-water swimming — and that a sudden spike in heart rate during the first ten minutes of a swim may be an early warning signal worth acting on immediately. The same study also found that a brief VR simulation of open-water swimming triggers a genuine and measurable stress response in the body's nervous system, even when the person watching it feels no conscious anxiety, pointing toward a safe and practical new method for assessing how individuals react to the physical and psychological pressures of open-water swimming before they ever enter the sea.
Why Drowning Prevention in Open-Water Swimming Needs Better Tools
Drowning kills approximately 240,000 people worldwide every year, making it the third leading cause of accidental death globally and one of the leading causes of death among children and young people. In Japan, long-distance swimming in the sea has long been part of school physical education, valued for the fitness, confidence, and water safety skills it develops in children. But safety concerns have led more schools to scale back or abandon these programs, leaving a gap in water competency education with no clear way to fill it. Part of the problem is that open-water swimming is genuinely harder to supervise than pool swimming. Currents, waves, varying water temperatures, and the physical and psychological demands of sustained swimming far from shore create conditions where physiological problems can develop quickly and without warning. In competitive triathlon — a sport involving a swimming leg in open water — cardiac arrest occurs at a rate of 1.74 per 100,000 participants, and two-thirds of those incidents happen during the swim. Detecting when a swimmer is in trouble before a crisis develops requires monitoring tools that work reliably in real-world open-water conditions. This study set out to test two such tools: a real-time wearable heart rate monitoring system worn during actual long-distance sea swimming, and a virtual reality simulation of open-water swimming used to observe acute physiological stress responses in a laboratory setting.
Heart Rate Predicts Who Struggles — and VR Triggers a Real Stress Response
For the open-water monitoring component, 40 undergraduate students at Kawasaki University of Medical Welfare took part in a nearly three-hour long-distance swim at Kitaura Beach, Japan, wearing a wearable heart rate sensor positioned on the temple that transmitted data in real time to a monitoring boat following the swimmers, which in turn relayed it to a base station on the beach staffed by a medical doctor, a paramedic, and a nurse. Swimmers were grouped by their performance in a 400m breaststroke time trial conducted before the sea swim. The results showed clearly that heart rate during the long-distance swim was significantly correlated with 400m breaststroke time — meaning that how fast a swimmer could cover 400 metres in the pool reliably predicted how hard their heart was working in the sea. What did not predict this was peak oxygen uptake, the standard laboratory measure of aerobic fitness. This is a notable and practically important finding: a swimmer can have excellent cardiovascular fitness in the general sense and still struggle in open water, and the pool time trial appears to be a better guide to open-water readiness than a laboratory fitness test. Two swimmers required rescue support during the swim, and their heart rate records revealed a telling pattern in both cases: heart rate surged sharply to around 170-175 beats per minute within the first ten minutes of the swim — well before either swimmer showed outward signs of distress significant enough to attract immediate attention. One was rescued by jet ski after sustaining that elevated heart rate for an hour before dropping out; the other was handed a rescue tube within minutes of staff noticing the spike, and their heart rate recovered rapidly as a result. For the VR component, 66 students immersed their legs in warm water while watching an immersive VR recording of open-water swimming through a head-mounted display. Heart rate variability measurements taken before and after the exposure showed a significant shift toward greater sympathetic nervous system activity — the body's internal stress response — during the VR session. Consciously, the students did not report feeling more anxious, as measured by a validated anxiety questionnaire. But their bodies told a different story, suggesting the VR environment was triggering an involuntary physiological stress reaction that the students themselves were not fully aware of.
Two Tools That Could Make Open-Water Swimming Safer
Taken together, the two components of this study point toward a more structured, technology-supported approach to safety management in open-water swimming programmes. Real-time heart rate monitoring during sea swims is technically feasible under calm conditions and clinically informative — the data from the two near-miss cases make a persuasive argument that rapid heart rate elevation in the first ten minutes of a swim should be a trigger for immediate supervisory attention, even in the absence of other visible warning signs. VR simulation, meanwhile, offers a way to observe how a person's body responds to the stress of open-water swimming in a setting where a medical team can intervene safely if needed — potentially useful as a pre-participation screening tool for identifying individuals who may be at higher physiological risk before they enter the water. The authors are careful to acknowledge the study's boundaries. The fitness measure used — a bicycle ergometer rather than a swimming-specific test — may not fully reflect aquatic aerobic capacity. Open-water environmental factors including currents and varying water temperature were not controlled. Wearable sensors worn in water are susceptible to movement-related interference. And the VR experience involved only leg immersion rather than full-body swimming, which means it did not fully replicate the physical sensations of actual open-water swimming. The data from the two rescue cases, while important, come from a small number of individuals and need validation in larger groups, particularly children, before any clinical or safety management conclusions can be drawn. This study was supported by JSPS KAKENHI (grant number JP23K02379) and the Sasakawa Scientific Research Grant from The Japan Science Society (grant number 2023-6025). The research was led by corresponding author Dr. Hiromi Yano of the Graduate School of Health Science and Technology and Department of Health and Sports Science, Kawasaki University of Medical Welfare, Kurashiki, Japan.
Article title: Feasibility of Physiological Assessments for Long-Distance Swimming Safety in Open Water Using Virtual Reality Settings
DOI: 10.2174/011875399X485793260720102253
Read the published article here: https://bit.ly/4y73Ria
The Open Sports Sciences Journal
10.2174/011875399X485793260720102253
Feasibility of Physiological Assessments for Long-Distance Swimming Safety in Open Water Using Virtual Reality Settings