Anyone who follows Game of Thrones knows that few things can set your heart racing quite like Valyrian Steel. Now there’s data to prove it.

The data comes courtesy of Brandon Ballinger, a data scientist working with researchers at the University of California, San Francisco. Mr. Ballinger built an Apple Watch app, called Cardiogram, that can track a user’s heart rate through the day. With the app, Mr. Ballinger has learned that his own heart jumps to more than 120 beats per minute when he eats a burrito.

...