June 24, 2025: The U.S. Navy is using $200 Oura fitness rings to monitor the health of sailors. The test subjects are 1,600 sailors serving aboard ships of the USS FORD carrier group. Those wearing the rings are volunteers. The rings enable navy researchers to study thing like how long and how well sailors sleep along with other health indicators. The anonymous data is transmitted to Starlink satellites overhead and back to navy researchers based in San Diego.

The origins of the Oura ring project date back to 2017when the navy suffered two ship collisions with civilian merchant ships. These incidents killed 17 navy sailors. There continue to be collisions and accidents aboard ships attributed to fatigue. This led to the Command Readiness, Endurance and Watch standing/ CREW, program developed by the Naval Health Research Center. Sailors were first equipped with wearable monitoring devices in 2021. These devices, like the Oura rings, did not generate any signals that would reveal the ring wearer of their ship's position to anyone.

One problem was that this study had no official backing and no budget. The study was started by officers in the Pacific Fleet and fleet staff seeking official recognition and a budget from the Department of Defense. The growing success of the health monitoring effort will eventually change that and bring recognition and budgets. At that point the only risk is official adoption bringing with it crippling bureaucracy and misuse of the data.

This is not the first Navy effort in this area. Back in 2014 the Navy finished a decade long research effort concluding that a half century old practice adopted to keep sailors on nuclear submarines alert while minding the nuclear reactors was in error. Back in the 1960s the navy noted that sailors monitoring nuclear reactors on subs got tired towards the end of their eight hour shift. So the navy adopted an 18 hour workday, with sailors only required to monitor the reactors six hours per shift. Despite this sailors still eventually got tired. Since 2005 the navy has been conducting research to find out why. Turns out that sailors working a schedule that was out of sync with the 24 hour day was in itself a source of fatigue. That was because the circadian rhythm for humans is based on a 24 hour day and there is no practical way to change that. For the circadian rhythm to work you must sleep on a regular schedule in order to be most alert and healthy.

The navy researchers also noted commercial firms had found that workers who changed shifts a lot also suffered from reduced alertness, productivity and morale. That’s all because the circadian rhythm cannot be fooled. The circadian rhythm is most efficient when people sleep at night, but you can work night regularly with some decrease in effectiveness if you stick with the night shift for a long time. The greatest losses in alertness and efficiency come when you constantly change the time you can sleep. Thus the navy’s traditional work schedule was the most inefficient available.

The navy tested a new submarine work schedule what respected the circadian rhythm and found, via sensors sailors wore during testing, that alertness was much improved and opinion surveys found morale was much higher as well. Sailors tending the reactors still got tired towards the end of their shift, but not to the extent they experienced while living and working with an 18 hour day. The navy put submarine crews on a 24 hour day, always working the same shift and thus sleeping on a regular schedule. The new schedule was much appreciated because it didn’t fight the circadian rhythm and the sailors quickly felt the beneficial impact of that.