LONDON (Reuters) – World Athletics Championships organizers rebuffed criticism from Usain Bolt about his starting blocks in the 100 meters on Saturday, insisting they had been checked and were the same model used in Beijing two years ago.

Bolt, who will seek to finish his matchless individual sprint career with a 100m gold medal in the London Stadium on Saturday night, was, unusually for him, highly critical of the blocks after his sluggish performance in Friday’s first round.

“That was very bad,” he told reporters after recovering from a dismal start to win his heat in 10.07 seconds.

“I stumbled a little bit coming out of my blocks. I’m not really a fan of these blocks. These are the worst blocks I have ever experienced. I have to get the start together as I can’t keep doing this.”

Pressed on what exactly was wrong with them, he said: “It’s shaky. When I did my warm-up and pushed back, it fell back. It’s just not what I’m used to. It’s not as sturdy.”

Asked for a response to the criticism, a spokesman for the world governing body, the IAAF, said: “The starting blocks here in London are exactly the same model as were used at the last world championships in Beijing.

“The starting equipment including the blocks are checked after each session.”

Bolt will run in the third semi-final on Saturday night, with the final to be staged two and a half hours later.

He is seeking his fourth gold in the event, having won at every world championships since 2009 apart from 2011 in Daegu when he was disqualified for a false start.