Your treadmill can tell you a lot about your life. Calories burned? Check. Distance? Check. How much longer you need to be stuck in this sweaty gym? Sigh, check. But, new research suggests it could also be a window into something a little more morbid: Your treadmill performance can predict how soon you're going to die. The study, published in this month's Mayo Clinic Proceedings, looked at data for 58,020 people between the ages of 18 and 96. Everyone in the study had been referred for an exercise stress test between 1991 and 2009, but no one had been diagnosed with heart disease beforehand. Researchers had participants undergo the classic treadmill stress test, including measurements of heart rate, blood pressure, and many other factors. Using these data (and an equation formulated within the study), the researchers calculated what they termed "FIT Treadmill Scores" for each participant. Those scores were then matched up with data about which participants had died during the course of the 18-year study. Scores ranged from 200 (those individuals who were the most successful on the fitness test) to -200. Results showed that those with scores anywhere above zero had much better survival estimates, and those who scored above 100 had just a 2% mortality risk for the next 10 years. Once people went below zero, however, things didn't look as great. In particular, having a score below -100 was associated with 38% risk of dying in the next 10 years. Of course, this is just a prediction, not a guarantee. But, it is an eerily accurate one: Even after accounting for other factors, such as long-term markers of diabetes and traditional risk factors for heart disease, participants' low FIT scores were strongly associated with the likelihood of their deaths. While correlation doesn't always equal causation, it's hard to ignore the connections in this case. And, although predictive tests like this have existed before, they focused on individuals with confirmed heart problems and only applied to shorter lengths of time. So, if you're curious — or worried — about how long you'll live, you might want to hit up the gym. Or, you could always just ask your friends.