As part of a racing event, ten hurdles of 42 inches (106.7 cm) in height are evenly spaced along a straight course of 110 metres.

Fallen hurdles do not carry a fixed time penalty for the runners, but they have a significant pull-over weight which slows down the run.

Aries Merritt of the United States holds the current world record of 12.80 seconds, set at the Memorial Van Damme meet on 7 September 2012 in Belgium.

In 1935, the T-shaped hurdles were replaced by L-shaped ones that easily fall forward if bumped into and therefore reduce the risk of injury.

The 8-step start persisted from (at least) the 1950s to the end of the 20th century and included such World- and Olympic champions as Harrison Dillard, Rod Milburn, Greg Foster, Renaldo Nehemiah, Roger Kingdom, Allen Johnson, Mark Crear, Mark McCoy, and Colin Jackson.

Chinese star Liu Xiang won the 2004 Olympics and broke the world record in 2006 utilizing an 8-step approach, but he switched to 7-steps by the 2011 outdoor season.

After the 2010 outdoor season, American Jason Richardson trained to switch to a 7-step start and went on to win the 2011 World Championship.

American Aries Merritt trained in Fall 2011 to switch from 8 to 7, and then had his greatest outdoor season in 2012 – running 8 races in under 13 seconds – capped by winning the London 2012 Olympics and then setting a world record of 12.80.

[1] Of the 10 men with the fastest 110m hurdle times in 2012, seven used 7-steps, including the top 4: Aries Merritt, Liu Xiang, Jason Richardson, and David Oliver.

In American high school track and field and at many international Under-20 athletics competitions, the 110 metres hurdles are mostly the same as their professional counterparts.

The newly made college hurdler needs to learn how to shorten their strides so they can take off the ground from farther away to clear a 42-inch barrier.