First let's get our semantics straight. This list is about trends, not fads. The difference being that a fad is a phenomenon that blows up quickly, lasts only for a short time, then, fades away. A trend is something that gains momentum and can create long-term impact in the way people think or behave. In other words, a trend is a "movement."
When it comes to physical fitness, I've always opted for the tried, true and traditional. I'm perfectly happy with my light weight-training and a good jog in the park. But apparently I've been missing out on a whole new wave of inventive, fun and sometimes hilarious workout routines -- from "aerial yoga" to "booty ballet!"