DÜSSELDORF, Germany (AP) — Many professional athletes are doing their bit to boost public health during the coronavirus pandemic. There has been an explosion of athletes offering free online fitness classes and tips to an audience isolated at home. It helps others keep fit and it’s a way for sports like track and field to stay relevant in a year without the Olympics. The governing body of track and field has been left with an empty schedule as meets around the world have been canceled. It is filling the gap with a range of online exercise tips and educational resources.