In this episode, Amar tries out a muddy endurance obstacle course to get to the bottom of their huge surge in popularity. He also puts carb-loading to the test, to see if it's the best way to get round with energy to spare. Anna finds out why bringing up the rear in a group run isn't something to be ashamed of, as she investigates the new exercise trend called LISS - Low Intensity Steady State, which barely makes you break a sweat. Anna also finds out how delaying breakfast until after you exercise can make you burn double the fat. Whatever the exercise, Anna and Amar are on a mission to help viewers get their fitness goals back and on track.