You're running on the treadmill when the trainer tells you that you need to speed up further. As you're cooling down after your workout, the trainer designs your routine for the next day. You did well, it tells you. Yes, you read that right. The trainer isn't a human. It's an artificial intelligence-driven platform that gleans what your body needs and what it's capable of, and then designs your workouts and oversees your routines, even offering motivation when you need it.