Bolt's starting-block concerns no worry for IAAF

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Usain Bolt's criticism of the starting blocks in use at the IAAF World Championships in London has been rebuffed by athletics' governing body.

Bolt got away poorly in the 100 metres heats on Friday, relying on a push in the second half of the race to cross the line first and book his place in Saturday's semi-finals.

After the race, the Jamaican - seeking his fourth 100m World Championships gold - laid part of the blame for his sluggish getaway with what he deemed "the worst blocks I've ever experienced".

"I'm not really fond of these blocks. I think these are the worst blocks I've ever experienced and it was just not a smooth start," Bolt said after recording a time of 10.07 seconds.

"It's shaky - when I did my warm-up and pushed back it [the starting block] fell back. It's just not what I'm used to. Not as sturdy or firm."

In response to the criticism, an IAAF spokesperson affirmed the blocks are no different than two years ago, when Bolt won gold in the 100m and 200m in Beijing.

"The starting blocks here in London are exactly the same model as were used at the last World Championships in Beijing," the spokesperson said.

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

Bolt will conclude his career as an individual on Saturday, with the men's 100m final the climax of the day's second session at London Stadium.

The Jamaican will then attempt to take his gold-medal haul at World Championships to 13 in the 4x100m relay next weekend.