Want to live longer? Research reveals the top cardiac risk factor (and it’s not smoking)

Want to predict how long you’ll live? Knowing is impossible, but there are simple research-backed tests—tests you can do for free, at home—that provide indications. For example: You can do the sit-rise test. You can try to stand on one leg for 10 seconds. You can see how many pushups you can do. You can hang from a bar (or squeeze a tennis ball). Performing relatively poorly on any of those tests correlates to a significantly greater risk of premature death—information that is interesting, but…