swimming bicycling and running are three very popular sports. Some people like to do all three sports in one race. They can do all three in a triathlon triathlon means 'three sports.' In a triathlon the people must first swim for a mile (1.6.km). Then they must ride a bicycle for about 10 miles ( 16 km). And then they must run for three miles (4.8 km). You must be a very strong person to win a triathlon