We've all done it. We give ourselves an hour to get in a workout, then end up wasting nearly half of it -- running an errand or two, getting dressed at the gym, chatting with acquaintances we bump into along the way. Even with the best intentions, you can sidetrack your progress if you don't make good use of your time. Think you might be frittering away precious fitness time? Check out what three fitness experts identified as the top fitness time-wasters, and see where you can improve.