On Friday, an international court ruled that amputee sprinter Oscar Pistorius doesn't get a boost from his carbon-fibre prosthetic legs – called Cheetahs.

After 2 days of testimony from a team of sports scientists who conducted extensive testing on Pistorius and his Cheetahs, the Court of Arbitration for Sport overturned a previous ruling that had kept the South African off the track.

The decision means Pistorius can now compete against able-bodied runners and perhaps in the Beijing Olympics this summer.

New Scientist takes a closer look at the science surrounding the decision.

Do the prosthetic legs give Pistorius an unfair advantage over able-bodied runners?

Probably not, says Peter Weyand, a biomechanist at Rice University in Houston who led the testing. His team found that Pistorius burns just as much energy as other elite athletes. If the Cheetahs gave Pistorius an advantage, he would burn fewer calories while performing at the same level as other athletes.

To find out, Weyland's team measured how much oxygen Pistorius consumed as he ran at a moderate pace on a laboratory treadmill.

They found that although he used oxygen more efficiently than many elite runners, he wasn't off the charts, and many distance runners do better. "Does he run cheaper than everyone else? The answer is no," Weyand says.

The International Association of Athletics Federation (IAFF) also based their ban on the odd method of pacing Pistorius uses. Most 400-metre sprinters run the first half of the race faster than the second, while Pistorius is just the opposite – starting slow and gaining speed as the race goes on. "He can run a good 100 metres, a better 200 metres, and an even better 400 metres," Weyand says.

The IAFF assumed that his pacing meant he got an advantage from the Cheetahs as the race progressed, but treadmill tests showed that eventually Pistorius too loses speed. His prosthetic legs actually slow his starts.

See a video of amputee sprinter Oscar Pistorius in action during tests (Video courtesy of Rice University)

How did the IAFF get the science wrong?

The IAFF tested Pistorius and his prosthetics legs in the fall, but Weyand's team says they over-interpreted the results.

One claim – that Pistorius runs 25% more efficiently than able-bodied runners – simply isn't true, says Hugh Herr, a researcher at the Massachusetts Institute of Technology in Cambridge, US, who presented Pistorius's case.

That figure was based on an analysis of Pistorius sprinting on a treadmill at 9 metres per second. At that speed, a runner must produce some energy without oxygen, or anaerobically. The problem was that IAFF used a unreliable test to measure the anaeorobic energy that Pistorius burned while sprinting, says Herr.

Do his prosthetic legs return more energy than human legs?

There's no way to know, says Weyland. The IAFF had claimed that the carbon-fibre Cheetahs returned six times more energy than a human ankle. "The blade is a really simple mechanical device, but a biological one is a lot more complicated," he says. Dozens of muscles and tendons interact with every step, so it's impossible to assess the mechanics at a single joint, says Weyland. "There are too many unknowns."

What's next?

For Pistorius, the ruling means that he can now race in sanctioned events against able-bodied runners. But it's unclear whether he will race in the Beijing Olympics. "The poor guy's been fighting this for six months, instead of training," Weyland says.

Weyland and Herr's team plans to publish their findings in a peer-reviewed journal. As the Cheetahs can be flexed and folded to gauge their mechanical properties in ways that human legs can't, "it's a great way for us to test our ideas about running", Weyland says.