With more than 4,200 athletes from 166 countries and ticket sales on track to top 2.5 million, this year's Paralympic Games are set to be the biggest in history. Here's the background you need to know going into the competition, which starts August 29 and lasts until September 9.
* The forerunner of the Paralympic Games was organized in 1948 at the British military's Stoke Mandeville Hospital by Sir Ludwig Guttmann -- a Jewish neurologist who escaped Nazi Germany with his family just weeks after Kristallnacht. Rather than sedating paralyzed patients and restricting them to bed, Guttmann saw physical activity as a way to rebuild both the strength and self-respect of injury victims. The first competitors in 1948 were British World War II veterans being treated for spinal cord injuries. Dutch veterans took part with British in 1952, making it the first international competition of its kind.
* The first official "Paralympic Games" -- parallel to the Olympics and open to competitors other than injured war veterans -- were held in Rome alongside the 1960 Olympic Games. Some 400 athletes in wheelchairs represented 23 countries in eight sports. Athletes with different disabilities have been included since 1976 and are grouped by their impairments.
* Disabilities of Paralympic athletes are now grouped into six broad categories: wheelchair, amputee, cerebral palsy, intellectual disability, visually impaired, and "others" -- which includes dwarfism, multiple sclerosis, and congenital deformities.
* In track events, the winner is the fastest athlete to complete a race. But in field events -- such as shotput, javelin, and discus throw -- results are "factored" to take into account the impairment of each competitor. For example, after each javelin throw an athlete receives points based on a combination of the distance and their level of impairment. The gold medal goes to the athlete with the most number of points.
* Wheelchair Fencing includes three different weapons -- epee, foil, and saber. The sport was developed at Stoke Mandeville Hospital -- birthplace of the Paralympics -- by injured British soldiers. Wheelchairs are fastened to the floor in a way that gives freedom of movement in the body for fast-moving techniques and tactics.
* Wheelchair Rugby was invented in the 1970s by quadriplegic Canadian athletes looking for an alternative to Wheelchair Basketball. Wheelchair Rugby originally was known as "murderball" due to its aggressive, full-contact nature.
* Five-A-Side Football is soccer played by athletes with visual impairments. A special ball with a bell inside makes noise as it moves. The soccer pitch is surrounded by a rebound wall and there are no throw-ins. There also is no offside rule. All outfield players wear eye shades to ensure they compete on equal terms.
* Goalball is a kind of handball for visually impaired athletes. The ball -- the size of a basketball but twice the weight -- has a bell inside to the guide players, who also wear eyeshades to equalize the playing field. Tactile floor lines help orient players as they try to throw the ball into the goal or use their bodies to block shots by their opponents.
* Sitting Volleyball emerged in the Netherlands during the 1950s as a sport that injured soldiers could play. A combination of volleyball and a German game called sitzbal, players are required to maintain contact between their pelvis and the floor at all times. The net is just over one meter in height.
* Since Iran made its Paralympic debut in Seoul in 1988, its men's Sitting Volleyball team has won gold five out of six times. The team has a running rivalry with Bosnia-Herzegovina, which defeated Iran 3-2 in the 2004 final. Iran won back gold at the 2008 Paralympics in Beijing, while Bosnia-Herzegovina won silver and Russia bronze.
* Britain's Martine Wright, a member of the women's Sitting Volleyball team, lost both her legs in the July 7, 2005, terrorist bombing of the London Underground's Circle line. Since becoming the most badly injured female survivor of Britain's worst terrorist attack, Wright has gotten married, given birth to a boy, and learned to pilot an airplane. She also has learned to ski and skydive.
-- Ron Synovitz