Johannesburg - Olympic 400 metres champion LaShawn Merritt says he is concerned about the progress made by amputee sprinter Oscar Pistorius in the last few seasons.
"He is getting better every year," the American told the insideworldparasport website.
"I haven't really been keeping up with it, but I don't know how the judge made a ruling on it and what goes on with the prosthetic legs."
Pistorius, who hopes to compete at the London Olympics, was cleared by the International Association of Athletics Federations (IAAF) to compete against able-bodied athletes in 2008.
Since his clearance, Pistorius has improved his personal best by well over a second to his career record of 45.07.
He reached the men's 400m semi-finals at the World Athletics Championships in Daegu, South Korea, last year and secured a silver medal as part of the SA 4x400m relay squad.
"Technology gets better every day," Merritt told the website.
He said he hoped the IAAF would monitor any changes made to Pistorius' carbon-fibre blades.
"I just hope the federation keeps track of what is happening with him just so it is fair."