From a gymnastics masterclass to a tennis knockabout, a fun run to a competitive youth athletics meeting, stars from around the world got involved in events on Saturday to celebrate sport. Five-time Olympic gold medal winning gymnast Nadia Comaneci and a host of Olympic champions and medalists including Felix Sanchez (athletics), Luciana Aymar (hockey), Gabriela Sabatini (tennis), and IOC President Thomas Bach (fencing) got involved in events in Lausanne on the eve of the annual Olympic Day global celebration of sport.