Race walking varies from running in that the participant must keep constant touch with the ground and must straighten the leading leg as the foot makes contact with the ground. It must remain straight until the leg is able to pass beneath the torso. The heel should make first contact with the ground and then be lifted while making forward progress. There are two types of race walking: Free Race Walking and Limited Race Walking. In free race walking, the participant can decide when to start and stop running. In limited race walking, a signal is given at regular intervals during the race. The participant must begin and end within those signals. The race distance for men is 10 kilometers while that for women is 5 kilometers. In addition to the standard races, there are giant race, marathon race, and half marathon race for both men and women. In a giant race, participants run together for as long as possible without stopping. The winner is determined by how far and how many times others drop out of the race. A man or woman who drops out of a giant race cannot later reenter it. A marathon race is completed in exactly 26 hours. Half marathon races are usually scheduled as two consecutive hours of racing followed by one hour of recovery time. There is also a 1-mile race called a "miler."