The holiday party invites are coming. Like it or not, they're descending upon your inbox one by one and taking over your calendar. As such, keeping up with exercise may seem like an insurmountable challenge. But, while it may be true that you don't have time to go running, do yoga and sneak in a Spinning class, you do still have time to fit a workout into your already-packed schedule. You just need the right (read: short) workout.