Bolt happy to thunder into retirement

Jamaican sprint great Usain Bolt said he has no regrets about his decision to retire from athletics in 2017 because he has accomplished everything he wants to in the sport.

Bolt will hang up his spikes following the world championships in London in August, bringing down the curtain on a career that has delivered eight Olympic gold medals.

"I've done everything I wanted to do in the sport ... there's nothing left to accomplish," Bolt said on the red carpet at the Laureus World Sports Awards in Monaco on Wednesday, where he was named Sportsman of the Year.

"I asked (former US sprinter) Michael Johnson the same question, 'Why did you retire when you were on top?'. He said the same thing - he had done everything he had wanted to do in athletics so there was no reason to stay in the sport. Now I understand what he means."

Bolt completed a triple championship of 100m, 200m and 4x100m Olympic titles at last year's Rio Games, but had his Beijing 2008 relay gold stripped last month after teammate Nesta Carter's retested sample showed traces of a banned substance.

The 30-year-old Bolt fired his international team to victory in the inaugural Nitro Athletics Series in Melbourne last week. He ran his first individual race of the year, burning away from a modest field for an easy win in the 150m sprint.

"I just wanted to run and to be part of it," he said. "I had to take it easy because I wasn't at the level I would usually be. It was the first time I had competed at this time of the year."

Meanwhile, the embattled Carter has filed an appeal to the Court of Arbitration for Sports after he was retroactively found guilty of doping at the 2008 Beijing Olympics, his lawyer said on Wednesday.

Carter is awaiting a date to appear before the CAS for his appeal, lawyer Stuart Stimpson said after confirming the appeal had been submitted to the Switzerland-based body.

"Yes, it was sent electronically today and the hard copies (sent by courier) will get there tomorrow, so the documents have been filed," Stimpson said.

"We've paid our fees and we met our deadline."

Carter retroactively tested positive for the banned stimulant methylhexaneamine in 2008 and on Jan 25 was stripped of his 4x100 gold medal along with teammates Bolt, Asafa Powell and Michael Frater.

The filing of the appeal came four days after the 2013 world championship 100m bronze medalist made his competitive return by anchoring his MVP track club's 4x100m team to second place at the Milo Western Relays in Montego Bay, Jamaica.