Can an athlete with two prosthetic legs run the 100m more easily than an athlete with just one? Is it fair to pit athletes with visual impairments against those with learning difficulties but 20/20 vision?
Compared to the Olympics, the Paralympics, which begin on Wednesday, present a real challenge when it comes to deciding who should race with whom.
Some of the 20 sports featured at the event are relatively straightforward: football five-a-side, for example, is for athletes with visual impairments and all of them, except the goalkeeper, wear a blindfold to ensure fairness.
But other disciplines, like athletics, can be a maze to navigate.
Track athletes are represented by the letter T plus a classification number, while field competitors have F then a number.
In the 100m for men, there are 15 separate events.
- Three for athletes with different degress of visual impairment (T11, T12, T13).
- Five for runners with cerebral palsy or other conditions affecting muscle control and co-ordination (T34, T35, T36, T37, T38)
- Three for leg and arm amputees (T42, T44, T46)
- Four for wheelchair racers (T51, T52, T53, T54)
Swimming also uses a letter and number classification to represent the type of stroke and the degree of disability, with the lower the number indicating a more severe impairment.
But where there are too few competitors in the same category, athletes with different degrees of disability are sometimes grouped together, which critics say does not create a level playing field.
In other cases, events for certain categories are dropped altogether.
Austrian wheelchair racer Thomas Geierspichler won Paralympic gold in the 1,500m in Athens in 2004 and followed up with a marathon win -- and world record -- in Beijing four years later.
In London, however, the 36-year-old will only compete in the 100m, 200m, 400m and 800m, after the T52 class for wheelchair athletes with impairments in both lower and upper limbs was dropped.
"Severely impaired athletes must now fight against moderately impaired ones. That's unfair. Medal chances have become unrealistic," Geierspichler was quoted as saying in an interview with the Austria Press Agency.
"I've been training in long-distance and marathon for 14 years. To find out at such short notice that these don't exist in my category anymore is insane.
"It's like if you told (Ethiopian former Olympic and 10,000m world champion) Haile Gebrselassie he had to run the 400m."
While the new developments are designed to make races as exciting as possible for the viewing public, Geierspichler argued that "it removes prospects for seriously impaired athletes".
"I can promise I will fight till I drop. But just getting into a final will be an achievement... the time was too short to switch (disciplines)."
Even South African sensation Oscar Pistorius, nicknamed "Blade Runner" because he runs on carbon fibre blades, remains controversial ahead of the London Games.
Earlier this month, he became the first double-amputee to compete in the Olympics, but at the Paralympics he will be running against single amputees, like T44 100m world record holder Jonnie Peacock.
"I find that really quite unfair because obviously he's got two (prosthetic legs) and the other person can only run as fast as their other leg is going to take them," athlete Kelly Cartwright, of Australia, told broadcaster ABC.
The 23-year-old lost a leg to cancer and plans to compete in the 100m and the long jump in London.
"I see him as a really great, fast athlete but also I can see the disadvantage for the other athletes as well."
"The public wants to see fit, model athletes," added Austrian swimmer Andreas Onea.
"Seriously handicapped people in wheelchairs are harder to market than an athlete sprinting on prosthetic legs. But wheelchair racers with two functioning arms can also be top athletes," he told Austrian daily Der Standard.
The 20-year-old has no left arm and is set to compete in the 100m breaststroke, 100m butterfly and 200m individual medley.