In the U.S. Armed Forces, when people are tired, they keep on working. "We have a lot of type-A personalities in the military who take it personally to get the job done no matter what the task," Lt. Colonel Bradley Ritland, deputy chief of the Military Performance Division at the U.S. Army Research Institute of Environmental Medicine, tells Popular Mechanics. "You do have a set percentage who are hesitant to report feeling tired or to report feeling an injury. They think that would impact their career, or feel like they're letting a colleague down, or feel they wouldn't be contributing as best they can to the mission." Now, machine learning technology from the Johns Hopkins University Applied Physics Laboratory may eventually be able to report in real time whether those soldiers need a break or identify who is at risk for injury.