Sumo wrestling originated in Japan over 2,000 years ago and grew in popularity during the early 1600s. Sumo wrestlers, known as rikishi, compete in a ring called a dohyo. There are six main tournaments held every year. Rikishi undergo rigorous training that includes leg stomping 500 times per day and pushing against wooden poles. Matches follow strict rules - a wrestler loses by stepping out of the ring or touching the ground with any part of their body other than the soles of their feet. Rikishi wear an elaborate belt called a mawashi during matches and practice.