How Reunion's Trail Runners Are Advancing Sports Medicine Through a Hospital-Backed App

Reunion's Trail Runners Feed Medical Research Through Free University Hospital Platform A decade of failed recruitment attempts ended when the University Hospital Center (CHU) of Reunion launched Onatrail in late August 2026. The digital platform collects health and performance data from recreational trail runners across the island, offering free access to training plans, post-run analysis, and smartwatch integration in exchange for participation in medical research on endurance sports. The platform is the culmination of work by Dr. Nicolas Bouscaren, a public health physician at the CHU and the project's scientific director. Bouscaren had faced a persistent obstacle: recruiting enough participants to conduct rigorous studies on trail running and its physiological effects. Previous attempts to build research cohorts through social media and influencer outreach had failed to generate sufficient numbers. Onatrail was built as a direct response to that recruitment challenge, embedding data collection into a tool designed to benefit users themselves. The underlying logic is reciprocal. Runners who register gain access to personalized training guidance, performance analytics, and mathematical models designed to help them plan outings, adapt to weather conditions, and manage nutrition and hydration. In return, they contribute their health metrics and training data to a database the CHU will analyze through what Bouscaren describes as participatory science, combining epidemiological studies, field research, and data science approaches. One hundred runners had registered since the platform opened at the end of August, and hospital officials have set a target of between one thousand and two thousand active users. The research agenda centers on conditions that long-distance trail runners frequently encounter. Initial focus areas include pelvic floor dysfunction in women, sleep and recovery patterns, relative energy deficiency syndrome, pain, inflammation, and muscle recovery. These are not theoretical concerns. Bouscaren noted that some participants in the Grand Raid, a grueling multi-day ultramarathon held on Reunion, have exhibited physiological states comparable to those of patients admitted to intensive care units, with their kidneys, livers, hearts, and muscles pushed to extreme limits. The medical literature on endurance racing documents how such efforts can drive athletes into metabolic zones characterized by severe fatigue and sleep deprivation, creating conditions that researchers have not yet fully mapped. By contrast, the CHU's research team aims to document what Bouscaren calls the unsuspected resilience capacities of the human body under these extreme conditions. Data collected through Onatrail could establish baseline patterns for injury risk and identify individual vulnerability zones based on runner profiles. Such information might help athletes avoid the consequences of overtraining or premature return to running after injury, outcomes that many runners have experienced without adequate warning. For the hospital system, the platform offers a pathway to position Reunion as a reference center for trail running research at the national and potentially international level. The timing of the launch, coinciding with the approach of the Grand Raid season, has provided natural visibility. The project is funded by the Reunion Regional Council and the European FEDER fund, with a current budget of 900,000 euros allocated to development and operation. Significant questions remain unanswered. The platform has been live for only weeks, and the volume of data currently available is minimal. Whether the health information collected from runners on Reunion's trails will prove sufficient to reshape how sports medicine understands the limits of human physiology is far from settled. The CHU has committed to the research agenda, but the real test will come as user numbers grow and longitudinal data accumulates (the platform's first full Grand Raid season will be the earliest meaningful checkpoint). Only then will it become clear whether this free tool, offered to ordinary recreational athletes, can generate findings that advance medical knowledge in ways that previous, smaller-scale studies could not.