Able-bodied or disabled? Hard to tell, isn't it? This is Grade IV Paralympic dressage rider Sophie Wells of Great Britain. Photo by FEI/Liz Gregg. 

Do I feel sorry for a person with a limp, a missing limb, or some other physical challenge? Yeah, I do -- until that person climbs in the saddle and proceeds to kick my able-bodied dressage-riding butt.

That's about the size of it when it comes to the elite riders whose physical disabilities disappear as if by magic when they're on horseback. The world's best dressage riders and other athletes who happen to have physical disabilities are currently vying for medals at the 2012 London Paralympic Games. Make no mistake: These are not a kinder, gentler Olympic Games. Paralympic athletes are tough, serious, and competitive. Here's a look at the Paralympic equestrian competition.

Like the Olympic equestrian events, Paralympic equestrian competition is conducted under the auspices of the International Equestrian Federation (FEI). The FEI writes the tests for para-equestrian dressage. Instead of levels, in para-dressage the divisions are called grades, and each grade corresponds to a degree of physical disability. The Grade Ia tests are for the most profoundly disabled riders and are conducted at the walk only. There are Grades Ib, II, III, and IV, with IV being the most advanced (for the least-disabled) and roughly equivalent to US Equestrian Federation Third Level, with walk, trot, and canter, lateral work including half-pass, half-pirouettes in walk, and simple changes of lead through the walk.

Prior to competing in FEI para-equestrian dressage, a rider must be "classified" into a grade at an official classification event, by specially trained officials. Of course no two disabilities are exactly alike, but the exhaustively detailed classification system ensures as level a playing field as possible.

Many para-equestrian competitors ride with special equipment that allows them to compensate for, say, a missing or weakened limb or side. Riders must obtain dispensation certificates, as they're called, in order to compete with equipment other than that permitted in standard FEI dressage competition. For instance, some para-dressage competitors carry two whips or have specially modified saddles or stirrup attachments,

Para-equestrian dressage riders come into the sport in various ways. Some are born with a condition, such as cerebral palsy. Others were accomplished able-bodied riders who became disabled after an accident. One of the best-known riders who is currently making the latter transition is 2008 U.S. Olympic dressage competitor Courtney King Dye, who suffered a severe traumatic brain injury in a helmetless fall from a horse two years ago. Although she did not make the 2012 U.S. Paralympic dressage squad, Dye has been competing in para-dressage and has stated that the Paralympics are a goal.

Of the four 2012 U.S. Paralympians, two were born with their disabilities and two developed them later in life. The 2012 U.S. Para-Equestrian Dressage national champion, the Grade II rider Rebecca Hart, was born with a condition called familial spastic paraplegia. Hart, 27, now lives in Unionville, Pa., so that she can train with Missy Ransehousen, the U.S. para-dressage chef d'equipe. Hart's mount for the 2012 Paralympics is Lord Ludger, a Holsteiner gelding owned by Missy's mother, the dressage Olympian Jessica Ransehousen.

First-time Paralympian Jonathan Wentz, 21, of Richardson, Tex., has cerebral palsy. His mount in London is the handsome Shire-cross gelding NTEC Richter Scale, owned by his coach, Kai Handt. The pair earned the 2012 U.S. national reserve title. Wentz competes in the Grade Ib division.

Donna Ponessa, 51, of New Windsor, NY, rode as a youngster but was diagnosed with multiple sclerosis during her college years. Her MS progressed to a rare form called Devic Disease. Ponessa competes with Wentz in the Grade Ib division. Ponessa's Paralympic partner is Western Rose, a nine-year-old Oldenburg mare owned by Wesley Dunham.

Dr. Dale Dedrick, 56, of Ann Arbor, MI, was a successful orthopedic surgeon and a Grand Prix-level dressage rider when she was diagnosed with lupus. The disease caused her to lose most feeling in her hands, thus ending her medical career. The Grade II Paralympian rides her own horse, Bonifatius, a fourteen-year-old Hanoverian gelding.

If you haven't seen these riders and their peers in action, prepare to be impressed and humbled. They sit better and are more effective riders than a lot of able-bodied types. And their horses are not necessarily sedate, push-button types either. I saw Lord Ludger at the award ceremony at the 2012 USEF Dressage Festival of Champions in Gladstone, N.J. (the Paralympic selection trials), and the big gelding was pretty worked up at the cheering crowds. These are not the placid mounts you may picture being used for therapeutic riding. And their riders are up to the challenge.

Follow the 2012 Paralympic equestrian competition at this link.